text:
Poison Idea

Poison Idea was an American punk rock band formed in Portland, Oregon, in 1980.

Formation, 1980s, and 1990s
Poison Idea was formed in 1980 by vocalist Jerry A. (aka Jerry Lang). The initial lineup consisted of Jerry A., Chris Tense (bass), and Henry Bogdan (later of Helmet) on drums. Jerry described this early version of the band, in which he sang and played sax, as a "kind of PIL thing" and only lasted a few shows. Jerry and Tense (now on guitar) then hooked up with Glen Estes (bass), and Dean Johnson (drums). Inspired by Black Flag and other early Southern California hardcore acts, they were further influenced by Discharge and Los Angeles's Germs. Germs singer Darby Crash's influence on singer Jerry A., vocally, lyrically, and philosophically, was considerable, and Poison Idea followed the Germs' extremist punk ethic. Tense was replaced within a year by Tom "Pig Champion" Roberts (guitar), formerly of the Imperialist Pigs but he would soon return to the band, this time on bass, replacing Glen Estes (later of Portland, Oregon punk/metal band Final Warning).

Poison Idea's debut, 1983's Pick Your King EP, was a short, lo-fi blast of hardcore fury. The jacket featured a "choice" of two kings, Jesus (front cover) and Elvis Presley (back cover).

In 1984, the group released the Record Collectors Are Pretentious Assholes 12-inch (the cover features Pig Champion's substantial vinyl collection). The record found the band incorporating subtle rock elements into their music, which was further honed on their contributions to two 1985 compilations, "Laughing Boy" on the Drinking is Great EP (on which appeared other Oregon punk bands Final Warning, Lockjaw and E-13), and "Typical" and "Die on Your Knees" on the Cleanse the Bacteria LP (compiled by Pushead for his own Pusmort label).

With the release of 1986's Kings of Punk LP, Poison Idea had fully moved beyond the breakneck hardcore of their early records to a potent, driving and ultimately more intricate and sophisticated hardcore/hard rock fusion that incorporated the accessibility of hard rock without sacrificing the power of hardcore.

Following the release of Kings of Punk, the lineup changed again and the band added lead guitarist Eric "Vegetable" Olsen and drummer Steve "Thee Slayer Hippy" Hanford from local thrash metal band Mayhem. The band then released War All the Time (named for the Charles Bukowski book) in 1987. After the release of War All The Time, Chris Tense departed and was replaced by Craig "Mondo" Lower, also formerly of Mayhem. War All the Time and the EPs that followed (the Getting the Fear 12-inch and the Filthkick 7-inch) found them further developing the rock/hardcore sound first established on Kings of Punk, which they would hone in 1990 with Feel the Darkness.

Membership in Poison Idea continued to fluctuate. Mondo and Vegetable departed. Charley "Myrtle Tickner" Nims joined on bass and on second guitar there was, briefly, Kevin "Kid Cocksman" Sanders and then Aldine Strichnine. They also established their own record label in 1989, American Leather (named for the Germs song), and released two records the same year: a reissue of their 1982 demo Darby Crash Rides Again and the Discontent 7-inch.

In 1990, the band released Feel the Darkness. After the album's release, Aldine Strycnine was thrown out of the band, and Mondo returned, this time on guitar, for the 1991 tour. Poison Idea then released Blank Blackout Vacant in 1992, and We Must Burn in 1993. By this time, their drinking habits and hard living were beginning to catch up with them: the band weighed in at about 1,300 lb. collectively, and Pig Champion in particular was very fat, often having to play sitting down. After the release of We Must Burn, Pig Champion announced he was no longer willing to tour. The band's final hometown show with Pig Champion was recorded and released as the Pig's Last Stand CD by Sub Pop in 1996. The group continued on briefly as a 4-piece (as documented on the 1995 Your Choice Live release) before calling it quits. Jerry and Thee Slayer Hippy would soon form a short-lived band with Jerry's wife, May May Del Castro, called The Gift. A few years later, Jerry resurrected Poison Idea with Dean Johnson, Chris Tense and new guitarist Ian Miller. This lineup appeared on 1998's Learning To Scream 7-inch but the band dissolved shortly afterwards.

Reformation and recent events
Jerry and Pig Champion resurrected Poison Idea again with new members in 2000 to record new material. This material was released in 2006 as The Latest Will and Testament LP. Prior to the album's release, on January 31, 2006, Tom "Pig Champion" Roberts was found dead in his home.

On October 6, 2008, Portland police arrested Steve "Thee Slayer Hippy" Hanford, 39, in connection with a string of pharmacy robberies in late summer.

In 2015, Poison Idea released the LP Confuse & Conquer on Southern Lord Records. The album featured the return of former guitarist Eric "Vegetable" Olsen and is, as of 2022, their last studio LP.

After a 19 month absence, the band returned for one show on July 21, 2018, at the Bossanova Ballroom in Portland, Oregon. It was in celebration of the release of Feel the Darkness 28 years prior. A remixed and remastered album including B-sides, outtakes, alternate mixes, plus Live in London, has been re-issued by American Leather / TKO Records.

In December 2018, Metallica performed a cover of Poison Idea's "Taken By Surprise," a track from Feel the Darkness.

It was stated that in Portland, at the Northwest Hesh Fest, September 19–21, 2019, the band would, "reportedly play their last-ever hometown show."

Steven "Thee Slayer Hippy" Hanford, the band's former drummer, died of heart attack at age 50 on May 22, 2020.

In 2022, Jerry A. Lang released a three-part autobiography entitled Black Heart Fades Blue through Rare Bird Books.

Last lineup

 * Jerry A – vocals
 * Jeff Walter – guitar
 * Andrew "The King Slayer" Stromstad – guitar
 * Chris "Spider" Carey – bass (died 2022)
 * Chris Cuthbert – drums

Former

 * Tom "Pig Champion" Roberts – guitar (died 2006)
 * Chris Tense – bass
 * Glen Estes – bass
 * Dean Johnson – drums
 * Henry Bogdan – drums
 * Jim Taylor – guitar
 * Charley "Myrtle Tickner" Nims – bass
 * Steve "Thee Slayer Hippy" Hanford – drums (died 2020)
 * Craig "Mondo" Lower – guitar, bass
 * Kevin "Kid Cocksman" Sanders – guitar
 * Aldine Strycnine – guitar
 * Matt Brainard – guitar
 * Ian Miller – guitar
 * Andy Kessler (a.k.a. Joe Spleen) – guitar
 * Rob "Rawbo Nox" Hume – bass (died 2021)
 * Natalie Lucio – bass
 * Gordon Scholl – drums
 * Nathan "Skinny" Richardson – drums
 * Alexa "Barbie" Grey – drums, live (2016)
 * Eric "Vegetable" Olsen – guitar
 * Brandon Bentley – guitar
 * Mickey Widner – drums
 * Eric Roll – guitar

Studio albums

 * 1986 Kings of Punk LP (originally released on Pusmort Records)
 * 1987 War All the Time LP (originally released on Alchemy Records (U.S.))
 * 1990 Feel the Darkness LP (originally released on Vinyl Solution and American Leather)
 * 1992 Blank Blackout Vacant LP (originally released on Taang Records and Vinyl Solution)
 * 1993 We Must Burn LP (originally released on Vinyl Solution and Tim/Kerr)
 * 2006 Latest Will and Testament CD/LP (originally released on Farewell Records / Network of Friends)
 * 2015 Confuse & Conquer CD/LP (released on Southern Lord Records)

Singles and EPs

 * 1983 Pick Your King 7-inch EP (Fatal Erection, American Leather, TKO Records)
 * 1984 Record Collectors Are Pretentious Assholes 12-inch EP (Fatal Erection)
 * 1988 Filthkick 7-inch EP (Shitfool, TKO Records)
 * 1988 Getting the Fear 12-inch, 7-inch EP (Rockport, TKO Records)
 * 1989 Just to Get Away 7-inch Picture Disc Single (American Leather)
 * 1989 Darby Crash Rides Again 7-inch EP (American Leather, TKO Records)
 * 1989 Plastic Bomb Cassette Single (self-released)
 * 1990 Taken By Surprise 7-inch (Sub Pop)
 * 1990 Discontent 7-inch (American Leather)
 * 1991 Punish Me 7-inch, 12-inch & CD EP (Vinyl Solution, American Leather)
 * 1991 Dead Boy – A Tribute to Stiv w/ Jeff Dahl, 7-inch Single (Triple X Records)
 * 1991 Official Bootleg 2×7″ EP (Vinyl Solution, American Leather)
 * 1992 Return of the Rat/Up Front w/ Nirvana 7-inch (Tim/Kerr)
 * 1993 Religion & Politics Part 1 & 2 2×7″, 10-inch & CD EP (Insipid Vinyl, Tim/Kerr)
 * 1993 Single at X-mas w/ Ray & Grover 7-inch Single (Tim/Kerr)
 * 1993 Split Single w/ Babes In Toyland 7-inch Single (Insipid Vinyl)
 * 1993 Feel the Darkness (Remix) 7-inch Single (Dirter Promotions)
 * 1998 Learning to Scream 7-inch EP (Taang! Records)
 * 2007 Bipolar Hardcore Split 7-inch Picture Disc Single w/ Kill Your Idols (TKO Records)
 * 2013 2013 Black Friday X-mas Split w/Angry Snowmans 7-inch Single (TKO Records)
 * 2014 Triple Chocolate Penetration 7-inch Single RECORD STORE DAY 2014 (Voodoo Donut)
 * 2014 The Badge w/ Pantera Split 7-inch Single RECORD STORE DAY 2014 (Rhino Records)
 * 2015 Rövsvett 7-inch (Just 4 Fun)
 * 2016 Calling All Ghosts 12-inch (American Leather)
 * 2016 Something Better Single (self-released)

Collections

 * 1988 Get Loaded and Fuck Cassette (self-released) - reissued as "Ian MacKaye" in 1989
 * 1992 Pajama Party Covers Album Picture Disc & LP (Vinyl Solution, Tim/Kerr)
 * 1993 Dysfunctional Songs for Codependent Addicts CD (Tim/Kerr)
 * 1994 The Early Years CD (Bitzcore)
 * 2000 Best of Poison Idea CD (Taang! Records)
 * 2002 Kings of Punk / Record Collectors Are Pretentious Assholes CD (Rhythm Vicar)
 * 2005 Pick Your King / Learning to Scream LP (Reflex/Wolfpack)
 * 2017 Legacy of Dysfunction LP (American Leather Records)

Kings of Punk reissue series

 * 2011 Darby Crash Rides Again: The Early Years demos and rarities collection CD/LP (TKO Records & Southern Lord Records)
 * 2012 The Fatal Erection Years collection of rarities and early releases CD/LP (TKO Records & Southern Lord Records)
 * 2013 Kings of Punk expanded reissue  2×CD/2×LP (TKO Records & Southern Lord Records)
 * 2016 ''Latest Will And Testament" 10th Anniversary reissue CD/LP (TKO Records & American Leather Records)
 * 2016 War All The Time reissue CD/LP (TKO Records & American Leather Records)
 * 2018 Feel The Darkness expanded reissue 2×LP (TKO Records & American Leather Records)
 * 2019 Pig's Last Stand reissue 2×LP & DVD (TKO Records & American Leather Records)
 * 2020 Blank Blackout Vacant expanded reissue 2×LP (TKO Records & American Leather Records)

Live recordings

 * 1991 Live in Vienna 7-inch EP (American Leather)
 * 1991 Dutch Courage LP & CD (Bitzcore)
 * 1992 Keep Warm, Burn the Rich 7-inch EP (Bootleg)
 * 1993 Record Bootleggers Are Potential Millionaires LP (Bootleg)
 * 1995 Your Choice Live Series LP & CD (Your Choice Records)
 * 1996 Pig's Last Stand LP & CD (Sub Pop)

title: Poison Idea


text:
Talk:Bloodflowers

A trilogy? Has Robert Smith said this? I'd have though that if Pornography was part of a trilogy, it'd be "Seventeen Seconds > Faith > Pornography".

Bloodflowers and disintegration are linked inasmuch as they're his once-in-a-decade moans about getting old.

Robert Smith has said this, yes, and the DVD entitled "Trilogy" makes it pretty clear.

=mystery text= The recently added statement, "vendio 5 millones de discos" (It sold 5 million albums) should certainly be translated, if it is not innacurate. Having written that, I'm not entirely sure what to do with it. --Amanaplanacanalpanama 08:06, 3 August 2006 (UTC)

with Trilogy being the end.
What does that mean? The end of their recording career?

Circular links?
Does it not annoy anyone else that the links for Out of This World and Maybe Someday just come back to this page? eg the page essentially just refreshes? Do other pages redirect here or can't the links just go? You're on this page anyway after all. 79.71.220.61 (talk) 15:46, 13 March 2010 (UTC)

Done. 78.54.99.126 (talk) 19:45, 9 August 2010 (UTC) Adrian.Neumann

Changing songs last played etc.
Edits that may be inaccurerate have been made see diff. The diff shows changing songs last played etc. Jonpatterns (talk) 11:31, 5 July 2016 (UTC)

Missing track?
The track listing section lists a bonus Internet-only track ("Spilt Milk") as track number 11. But what is track 10? Is it "Coming Up," which is only referenced once on the page? — Preceding unsigned comment added by 2601:46:C803:4B00:80D2:E9B:9AD2:7662 (talk) 17:47, 1 May 2017 (UTC)

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Talk:Bloodflowers


text:
User talk:Saline

Welcome to the Wikipedia
Here are some links I find useful

 * Policy Library
 * Cite your sources
 * Verifiability
 * Wikiquette
 * Conflict resolution
 * Brilliant prose
 * Neutral point of view
 * Pages needing attention
 * Peer review
 * Bad jokes and other deleted nonsense
 * Village pump
 * Boilerplate text

Cheers, Sam [Spade] 06:10, 14 May 2004 (UTC)

title: User talk:Saline


text:
Dicks (band)

Dicks were an American punk rock band from Austin, Texas, formed in 1980 and initially disbanded in 1986. After the first breakup, singer Gary Floyd formed the band Sister Double Happiness, with drummer Lynn Perko, then later fronted a project called Black Kali Ma. In 2004, The Dicks reunited and were active until 2016.

The Dicks went through two incarnations in the 1980s, changing its lineup when Floyd moved from Austin to San Francisco in 1983. As a political band with Marxist lyrics during the Reagan Era, they did not shy from controversy. Floyd was one of a handful of openly gay musicians in the 1980s punk scene.

Austin lineup (1980–1983)
Dicks were formed in Austin in 1980 by Gary Floyd, Buxf Parrott, Pat Deason, and Glen Taylor. Their first single "Dicks Hate The Police", released in 1980, brought them much attention and is now regarded as a classic hardcore punk record. In the song Floyd sings from the perspective of a policeman who abuses his power by targeting minorities and abusing civilians.

Dicks often played shows with fellow pioneering Texas hardcore bands MDC, The Offenders, and The Big Boys; Dicks' full-length debut was the split album with The Big Boys, Live at Raul's Club. Dicks were among the first punk bands to address issues of homophobia and sexual identity, as in such songs as "Saturday Night at the Bookstore" and "Off-Duty Sailor".

San Francisco lineup (1983–1986)
In 1983, Floyd left Texas for San Francisco along with Debbie Gordon, the band's manager, who was considered a member of the band. Floyd and Gordon, along with new members Tim Carroll, Sebastian Fuchs, and Lynn Perko (formerly of all-women band The Wrecks), formed a second version of Dicks. The LP Kill From The Heart was released in 1983 on SST Records and These People followed in 1985 on Alternative Tentacles. The group disbanded in 1986, although occasional one-off reunion shows featuring the Austin lineup occurred through the 1980s and 1990s.

Breakup and continuing influence
The band remained influential in punk and underground circuits. San Antonio's Butthole Surfers had ended their 1984 album Psychic... Powerless... Another Man's Sac with the cowpunk anthem "Gary Floyd" in tribute to the Dicks' bandleader. Dicks saw a resurgence in popularity during the popularity of grunge when Seattle band Mudhoney released a cover of Dicks' "Hate The Police" on Sub Pop Records. Soon after, Chicago noise rockers The Jesus Lizard (three fourths of whom were also from Austin) released their cover version of Dicks' "Wheelchair Epidemic".

Gary Floyd later started Sister Double Happiness in San Francisco in 1986. After that band ended he formed and primarily played in Europe with The Gary Floyd Band; an overview of this material, "Backdoor Preacher Man", is available in the United States. Toward the late 1990s, Floyd played in Black Kali Ma, who released an album on Alternative Tentacles. Floyd later formed the band the Buddha Brothers, while Parrott and Deason went on to play in the Austin neo-bluegrass band Shootin' Pains and Trouser Trout, while Parrott and Taylor also played in Pretty Mouth. Perko went on to join Imperial Teen.

Reunion, disbandment and Gary Floyd's death (2004–2024)
In 2004, Dicks began playing regular reunion concerts in Austin and elsewhere. The lineup for the shows consists of the original Dicks, with the exception of Glen Taylor, who died in 1997. His role was filled by three other Austin guitarists: Mark Kenyon, Brian McGee, and Davy Jones. At the 2009 Austin Music Awards show, Jesus Lizard singer David Yow joined the band onstage for "Wheelchair Epidemic". At the same show, Dicks were inducted into the Texas Music Hall of Fame.

A documentary film, The Dicks from Texas, was released in 2015 about the Dicks and Austin, Texas punk scene along with a tribute album, The Dicks From Texas and Friends, with 27 bands covering 28 Dicks songs.

The Dicks announced that their final show would be October 30, 2016, at Grizzly Hall in Austin, Texas; however, due to popular demand, a second show was added the day afterward.

On April 30, 2024, Gary Floyd died after a series of health-related issues. He was 71, and was survived by his husband.

Members

 * Gary Floyd – vocals (1980–1986, 2004–2016); died 2024
 * Buxf Parrott – bass, guitar, vocals (1980–1983, 2004–2016)
 * Pat Deason – drums (1980–1983, 2004–2016)
 * Glen Taylor – guitar, bass (1980–1983); died 1997
 * Debbie Gordon – manager (1982–1986)

 * Tim Carroll – guitar (1983–1986)
 * Lynn Perko – drums (1983–1986)
 * Sebastian Fuchs – bass, vocals (1983–1986)
 * Mark Kenyon – guitar (2004–2016)
 * Brian Magee – guitar (2004–2005, 2016)
 * Davy Jones – guitar (2005–2015); died 2015

Timeline

Albums

 * Kill from the Heart LP (1983), SST Records
 * These People LP (1985), Alternative Tentacles

10"

 * Ten Inches 10-inch (2006), Delta Pop Music

Lives

 * Live at Raul's Club LP (1980), Rat Race – Split with The Big Boys
 * Dicks Live! Hungry Butt (2006), Hot Box Review

Singles, EPs

 * "Hate the Police" 7-inch (1980), R Radical Records
 * Peace? 7-inch EP (1984), R Radical Records: "No Fuckin' War"/"I Hope You Get Drafted"/"Nobody Asked Me"
 * Live at Raul's 2×7″ (1992), Selfless Records - split with The Big Boys
 * Hog 7-inch (2006), Delta Pop Music

Compilations

 * 1980–1986 CD (1997), Alternative Tentacles (compilation of out of print material)

Compilation appearances

 * "Gilbeau" on Cottage Cheese from the Lips of Death (1983), Ward 9 Records
 * "I Hope You Get Drafted" on the International P.E.A.C.E. Benefit Compilation (1984), R Radical Records
 * "Legacy of Man" on Rat Music for Rat People Vol. 2 (1984), CD Presents, Ltd

title: Dicks (band)


text:
User talk:Aramgutang

Current • Archive 1

ahh...the smell of a freshly archived talk page...

AfD nomination of List of significant others of Friends
An article that you have been involved in editing, List of significant others of Friends, has been listed for deletion. If you are interested in the deletion discussion, please participate by adding your comments at Articles for deletion/List of significant others of Friends (2nd nomination). Thank you. • 97198  talk  06:47, 26 October 2007 (UTC)

WikiProject Pharmacology Update
Here are a few updates in the realm of WikiProject Pharmacology:

 * The Pharmacology Collaboration of the Week has been changed to Collaboration of the Month, based on current participation levels. It is also more likely that articles collaborated on for one month are more likely to achieve featured quality than articles worked on for only a week or two.

 * The current Collaboration of the Month for November is Receptor antagonist. Please take a look at that article and contribute to it if you get a chance. Ideally, the article should adhere to the featured article criteria.

 * Therapies for multiple sclerosis is currently a featured article candidate. If you are familiar with the featured article criteria, please visit WP:FAC and review the article.

 * Anabolic steroid is the wikiproject's newest Featured Article, having been promoted on October 8, 2007.

 * Theobromine was delisted as a Good Article. The Peer review and GA reassessment discussions provide suggestions on improvement. Muscle relaxant was recently reviewed for Good Article status, but not promoted. Please see the full review full review here for details.

Dr. Cash 22:05, 31 October 2007 (UTC)

"Book"
Hi. (No pun intended ...) Can you help me out? An anonymous editor made a change to Arabic language, claiming that the Arabic word "kitab" (book) is used in Armenian. Is this true? Thanks. Cbdorsett (talk) 12:05, 17 December 2007 (UTC)
 * Thanks for your help. Cbdorsett (talk) 12:55, 19 December 2007 (UTC)

Little context in Category:Tourist attractions in Armenia
Hello, this is a message from an automated bot. A tag has been placed on Category:Tourist attractions in Armenia, by another Wikipedia user, requesting that it be speedily deleted from Wikipedia. The tag claims that it should be speedily deleted because Category:Tourist attractions in Armenia is very short providing little or no context to the reader. Please see Wikipedia:Stub for our minimum information standards for short articles. To contest the tagging and request that administrators wait before possibly deleting Category:Tourist attractions in Armenia, please affix the template to the page, and put a note on its talk page. If the article has already been deleted, see the advice and instructions at WP:WMD. Feel free to contact the bot operator if you have any questions about this or any problems with this bot, bearing in mind that '''this bot is only informing you of the nomination for speedy deletion; it does not perform any nominations or deletions itself. To see the user who deleted the page, click here''' CSDWarnBot (talk) 02:30, 2 February 2008 (UTC)

Fair use rationale for Image:WPI logo.gif
Thanks for uploading or contributing to Image:WPI logo.gif. I notice the image page specifies that the image is being used under fair use but there is not a suitable explanation or rationale as to why each specific use in Wikipedia constitutes fair use. Please go to the image description page and edit it to include a fair use rationale.

If you have uploaded other fair use media, consider checking that you have specified the fair use rationale on those pages too. You can find a list of 'image' pages you have edited by clicking on the "my contributions" link (it is located at the very top of any Wikipedia page when you are logged in), and then selecting "Image" from the dropdown box. Note that any non-free media lacking such an explanation will be deleted one week after they have been uploaded, as described on criteria for speedy deletion. If you have any questions please ask them at the Media copyright questions page. Thank you. Project FMF (talk) 03:44, 2 March 2008 (UTC)

Image:WPI logo.gif listed for deletion
An image or media file that you uploaded or altered, Image:WPI logo.gif, has been listed at Images and media for deletion. Please see the to see why this is (you may have to search for the title of the image to find its entry), if you are interested in it not being deleted. —PNG crusade bot (feedback) 21:45, 14 April 2008 (UTC)

Orphaned non-free media (Image:WPI logo.gif)
Thanks for uploading Image:WPI logo.gif. The media description page currently specifies that it is non-free and may only be used on Wikipedia under a claim of fair use. However, it is currently orphaned, meaning that it is not used in any articles on Wikipedia. If the media was previously in an article, please go to the article and see why it was removed. You may add it back if you think that that will be useful. However, please note that media for which a replacement could be created are not acceptable for use on Wikipedia (see our policy for non-free media).

If you have uploaded other unlicensed media, please check whether they're used in any articles or not. You can find a list of 'image' pages you have edited by clicking on the "my contributions" link (it is located at the very top of any Wikipedia page when you are logged in), and then selecting "Image" from the dropdown box. Note that all non-free media not used in any articles will be deleted after seven days, as described on criteria for speedy deletion. Thank you. NotifyBot (talk) 12:17, 17 April 2008 (UTC)

re:Olympic heat ranks - overall or specific?
Hi, the convention for the rank athletic events to be given as the position in the heat and for swimming events to give the overall rank is due to the differences in how next round qualifiers are decided in the two sports. In swimming qualifing competitors are decided only on a time basis, so if, e.g., heat 1 is is faster than heat 2 it is possible that all the competitors from heat 1 and none from heat 2 would get through to the next round. An example is Men's 50m freestyle. However in athletics qualifiers for the next round are decided by the first X athletes in each heat getting through, i.e. at least X athletes from every heat will get into the next round. Hopefully i've explained this without being too confusing but if not leave me another message and i'll try and find the right page on the olympic website to direct you to. Basement12 (talk) 10:35, 19 August 2008 (UTC)

Possibly unfree Image:Calayan_Rail.jpg
An image that you uploaded or altered, Image:Calayan_Rail.jpg, has been listed at Possibly unfree images because its copyright status is unclear or disputed. If the image's copyright status cannot be verified, it may be deleted. You may find more information on the image description page. You are welcome to add comments to its entry at if you are interested in it not being deleted. Thank you. Jordan 1972 (talk) 15:33, 18 October 2008 (UTC)

File copyright problem with File:Tom & Jerry-Piano Concerto 2.jpg
Thank you for uploading File:Tom & Jerry-Piano Concerto 2.jpg. However, it currently is missing information on its copyright status. Wikipedia takes copyright very seriously. It may be deleted soon, unless we can determine the license and the source of the file. If you know this information, then you can add a copyright tag to the image description page.

If you have uploaded other files, consider checking that you have specified their license and tagged them, too. You can find a list of files you have uploaded by following this link.

If you have any questions, please feel free to ask them at the media copyright questions page. Thanks again for your cooperation. Closedmouth (talk) 14:17, 16 September 2009 (UTC)

Speedy deletion nomination of File:Esperite under UV light.jpg

A tag has been placed on File:Esperite under UV light.jpg requesting that it be speedily deleted from Wikipedia. This has been done under section I2 of the criteria for speedy deletion, because it is an image page for a missing or corrupt image or an empty image description page for a Commons-hosted image.

If you think that this notice was placed here in error, you may contest the deletion by adding to the top of the page that has been nominated for deletion (just below the existing speedy deletion, or "db", tag; if no such tag exists, then the page is no longer a speedy delete candidate and adding a hang-on tag is unnecessary), coupled with adding a note on the talk page explaining your position, but be aware that once tagged for speedy deletion, if the page meets the criterion, it may be deleted without delay. Please do not remove the speedy deletion tag yourself, but don't hesitate to add information to the page that would render it more in conformance with Wikipedia's policies and guidelines. Logan Talk Contributions 23:53, 25 January 2011 (UTC)

Notification: changes to "Mark my edits as minor by default" preference
Hello there. This is an automated message to tell you about the gradual phasing out of the preference entitled "Mark all edits minor by default", which you currently have (or very recently had) enabled.

On 13 March 2011, this preference was hidden from the user preferences screen as part of efforts to prevent its accidental misuse (consensus discussion). This had the effect of locking users in to their existing preference, which, in your case, was. To complete the process, your preference will automatically be changed to  in the next few days. This does not require any intervention on your part and you will still be able to manually mark your edits as being minor in the usual way.

For established users such as yourself there is a workaround available involving custom JavaScript. With the script in place, you can continue with this functionality indefinitely (its use is governed by WP:MINOR). If you have any problems, feel free to drop me a note.

Thank you for your understanding and happy editing :) Editing on behalf of User:Jarry1250, LivingBot (talk) 19:17, 15 March 2011 (UTC)

File:Sevanavank locator map.png missing description details
Dear uploader: The media file you uploaded as: is missing a description and/or other details on its image description page. If possible, please add this information. This will help other editors make better use of the image, and it will be more informative to readers.
 * File:Sevanavank locator map.png

If the information is not provided, the image may eventually be proposed for deletion, a situation which is not desirable, and which can easily be avoided.

If you have any questions, please see Help:Image page. Thank you. Theo's Little Bot (error?) 10:08, 14 April 2013 (UTC)

The Wikipedia Library now offering accounts from Cochrane Collaboration (sign up!)
Cochrane Collaboration is an independent medical nonprofit organization consisting of over 28,000 volunteers in more than 100 countries. The collaboration was formed to organize medical scholarship in a systematic way in the interests of evidence-based research: the group conducts systematic reviews of randomized controlled trials of health-care interventions, which it then publishes in the Cochrane Library.

Cochrane has generously agreed to give free, full-access accounts to 100 medical editors. Individual access would otherwise cost between $300 and $800 per account. Thank you Cochrane!

If you are stil active as a medical editor, come and sign up :)

Cheers, Ocaasit | c 19:56, 16 June 2013 (UTC)

Notification of automated file description generation
Your upload of File:Armenia locator map template.png or contribution to its description is noted, and thanks (even if belatedly) for your contribution. In order to help make better use of the media, an attempt has been made by an automated process to identify and add certain information to the media's description page.

This notification is placed on your talk page because a bot has identified you either as the uploader of the file, or as a contributor to its metadata. It would be appreciated if you could carefully review the information the bot added. To opt out of these notifications, please follow the instructions here. Thanks! Message delivered by Theo's Little Bot (opt-out) 12:19, 4 January 2014 (UTC)

ArbCom elections are now open!
Hi, You appear to be eligible to vote in the current Arbitration Committee election. The Arbitration Committee is the panel of editors responsible for conducting the Wikipedia arbitration process. It has the authority to enact binding solutions for disputes between editors, primarily related to serious behavioural issues that the community has been unable to resolve. This includes the ability to impose site bans, topic bans, editing restrictions, and other measures needed to maintain our editing environment. The arbitration policy describes the Committee's roles and responsibilities in greater detail. If you wish to participate, you are welcome to review the candidates' statements and submit your choices on the voting page. For the Election committee, MediaWiki message delivery (talk) 22:16, 30 November 2015 (UTC)

Non-free rationale for File:Tom & Jerry-Piano Concerto.jpg
Thanks for uploading or contributing to File:Tom & Jerry-Piano Concerto.jpg. I notice the file page specifies that the file is being used under non-free content criteria, but there is not a suitable explanation or rationale as to why each specific use in Wikipedia is acceptable. Please go to the file description page, and edit it to include a non-free rationale.

If you have uploaded other non-free media, consider checking that you have specified the non-free rationale on those pages too. You can find a list of 'file' pages you have edited by clicking on the "my contributions" link (it is located at the very top of any Wikipedia page when you are logged in), and then selecting "File" from the dropdown box. Note that any non-free media lacking such an explanation will be deleted one week after they have been tagged, as described on criteria for speedy deletion. If the file is already gone, you can still make a request for undeletion and ask for a chance to fix the problem. If you have any questions, please ask them at the Media copyright questions page. Thank you. Nthep (talk) 13:43, 18 July 2016 (UTC)

Proposed deletion of File:Geghard locator map.png

The file File:Geghard locator map.png has been proposed for deletion because of the following concern: "Orphaned map."

While all constructive contributions to Wikipedia are appreciated, pages may be deleted for any of several reasons.

You may prevent the proposed deletion by removing the notice, but please explain why in your edit summary or on the file's talk page.

Please consider addressing the issues raised. Removing will stop the proposed deletion process, but other deletion processes exist. In particular, the speedy deletion process can result in deletion without discussion, and files for discussion allows discussion to reach consensus for deletion. ~ Rob 13 Talk 01:18, 25 February 2018 (UTC)

Proposed deletion of File:Odzun locator map.png

The file File:Odzun locator map.png has been proposed for deletion because of the following concern: "Orphaned map."

While all constructive contributions to Wikipedia are appreciated, pages may be deleted for any of several reasons.

You may prevent the proposed deletion by removing the notice, but please explain why in your edit summary or on the file's talk page.

Please consider addressing the issues raised. Removing will stop the proposed deletion process, but other deletion processes exist. In particular, the speedy deletion process can result in deletion without discussion, and files for discussion allows discussion to reach consensus for deletion. ~ Rob 13 Talk 01:18, 25 February 2018 (UTC)

Orphaned non-free image File:GavrilovMatrix.ogg
Thanks for uploading File:GavrilovMatrix.ogg. The image description page currently specifies that the image is non-free and may only be used on Wikipedia under a claim of fair use. However, the image is currently not used in any articles on Wikipedia. If the image was previously in an article, please go to the article and see why it was removed. You may add it back if you think that that will be useful. However, please note that images for which a replacement could be created are not acceptable for use on Wikipedia (see our policy for non-free media).

Note that any non-free images not used in any articles will be deleted after seven days, as described in section F5 of the criteria for speedy deletion. Thank you. --B-bot (talk) 17:17, 28 August 2018 (UTC)

title: User talk:Aramgutang


text:
Transgressive art

Transgressive art is art that aims to outrage or violate basic morals and sensibilities. The term transgressive was first used in this sense by American filmmaker Nick Zedd and his Cinema of Transgression in 1985. Zedd used it to describe his legacy with underground film-makers like Paul Morrissey, John Waters, and Kenneth Anger, and the relationship they shared with Zedd and his New York City peers in the early 1980s.

Definition
From an academic perspective, many traces of transgression can be found in any art which is considered offensive because of its shock value; from the French Salon des Refusés artists to Dada and Surrealism. Philosophers Mikhail Bakhtin and Georges Bataille have published works on the nature of transgression. Transgressional works share some themes with art that deals with psychological dislocation and mental illness. Examples of this relationship, between social transgression and the exploration of mental states relating to illness, include many of the activities and works of the Dadaists, Surrealists, and Fluxus-related artists, such as Carolee Schneemann – and, in literature, Albert Camus's L'Etranger or J.D. Salinger's The Catcher in the Rye.

In visual art
Transgressive artist Richard Kern began making films in New York City with actors Nick Zedd and Lung Leg in the early 1980s. Some were videos for musical artists, including the Butthole Surfers and Sonic Youth.

During the 1980s, artists such as Dread Scott created art that was so controversial that it ended up in the supreme court. In the case of Scott, United States v. Eichman, the Supreme Court ruled that it was unconstitutional for the government to prohibit an artwork that desecrates the American Flag. Another artist, Robert Mapplethorpe, caused the Director of the Contemporary Arts Center in Cincinnati to be put on trial for obscenity in 1990. Both cases were ruled in favor of the artists.

Among the most notorious works of transgressive art among the general public have been sculpture, collages, and installation art which offended Christian religious sensibilities. These include Andres Serrano's Piss Christ, featuring a crucifix in a beaker of urine, and Chris Ofili's The Holy Virgin Mary, a multi-media painting which is partially made of elephant dung.

Jeffrey Weiss of Artforum considers some of the work of Cy Twombly to be transgressive, citing "drawing as a form of scrawl".

In literature
The term can also be applied to transgressive literature as well. Examples include Trainspotting by Irvine Welsh, Blood and Guts in High School by Kathy Acker, American Psycho by Bret Easton Ellis, Fight Club by Chuck Palahniuk, Behead All Satans by MNM-DR, and J. G. Ballard's short story "The Enormous Space". These works deal with issues that were considered to be outside the social norms. Their characters abuse drugs, engage in violent behaviour, and could be considered sexual deviants.

Trangressive writing can also be reflected in non-fiction, such as in the writing style of Jim Goad.

In music
Subsequent transgressive artists of the 1990s overlapped the boundaries of literature, art, and music, including GG Allin, Lisa Crystal Carver, Shane Bugbee, and Costes. With these artists came a greater emphasis on life itself (or death) as art, rather than simply depicting a certain mindset in film or music. They were instrumental in creating a new type of visionary art and music, and influenced artists including Alec Empire, Cock E.S.P., Crash Worship, Usama Alshaibi, Liz Armstrong, Lennie Lee, Weasel Walter, Andy Ortmann, and the later work featured in Peter Bagge's comic Hate.

Rock and roll music has inspired controversy and been transgressive from its inception. As certain other musical genres grew in popularity, some transgressive artists used controversy to make a statement, gain attention, or make a profit (or a combination of these). Among certain musical genres and movements, offending modern sensibilities was an integral part of the music. Musical genres that utilize transgressive themes or music include genres such as shock rock, punk rock, trap, grindcore, black metal and death metal, and various bands within the avant-garde rock or experimental rock genre. Since the late twentieth century, the term has been most frequently applied to artists of musical genres such as hardcore hip hop, gangsta rap, and horrorcore. Eminem was a major subject of such controversy; his early works, most notably The Slim Shady LP (1999) and The Marshall Mathers LP (2000), were subjects of backlash surrounding their violent lyricism. Another major figure of criticism was rapper Tyler, the Creator, whose horrorcore-influenced debut studio album, Goblin (album), described graphic violence, which subsequently got his concerts banned from countries such as New Zealand and the United Kingdom. Though his former negative reputation softened to the masses, Tyler, the Creator and his former hip-hop group, Odd Future's music still faced major criticism for graphic lyrics present in their songs in the early 2010s.

Some musical artists use the controversy that surrounds transgressive art as a form of publicity.

Recent examples
Since the late 1990s, a new group of transgressive artists has emerged, such as the Canadian artist Rick Gibson who made a pair of earrings out of human fetuses and ate a piece of human testicle. In China, several artists have produced transgressive art; these include Zhu Yu (who published images of himself eating what appeared to be a human fetus) and Yang Zhichao (who is known for extreme body art).

title: Transgressive art


text:
Legendary Shack Shakers

The Legendary Shack Shakers (originally Those or Th' ) are an American rock band from Murray, Kentucky that was formed in 1995 by J.D. Wilkes. The original line-up formed the band out of a shared interest in rockabilly, blues and Western swing. Subsequently, the band gained prominence in the alternative country scene with a sound that encompassed rockabilly, blues, country and punk rock and a lyrical focus on Southern Gothic themes. Over time, the band's sound shifted to emphasize country music.

Formation
Singer and harmonica player J.D. Wilkes developed an interest in Delta blues music as a teenager living in Paducah, Kentucky as a result of disinterest in the decade's popular music styles, familiarizing himself with the music of Muddy Waters, Lightning Hopkins, Brownie McGhee and Charlie Patton before moving backward into older styles of music "to see the roots of the roots". He formed the Legendary Shack Shakers in Paducah with members of another band, Solid Rocket Boosters, who shared his interest in rockabilly, blues and Western swing; according to Wilkes, the only difference between the two bands was that they have different drummers. The original lineup of the Legendary Shack Shakers consisted of Wilkes, guitarists Nathan Brown and Brian Berryman, upright bassist Todd Anderson and drummer Chris Dettloff -- three of which were Murray State art majors, while the remaining two were a physics major and a psychology major. The band's line-up subsequently changed to Wilkes on lead vocals and harmonica, JoeBuck on guitar, Mark "The Duke" Robertson on upright bass, and Pauly Simmonz on drums, all of which alternatively played for local country music acts, most notably with Wilkes and JoeBuck touring as members of Hank Williams III's backing band.

Breakthroughs
Legendary Shack Shakers' 2002 album, Cockadoodledon't, established their prominence in the alternative country scene. After self-releasing their recordings, including Cockadoodledon't, the self-classified "insurgent country" record label Bloodshot Records reissued Cockadoodledon't in 2003. After JoeBuck left the band to join Hank Williams III's band full time, David Lee became the Legendary Shack Shakers' new guitarist, and the band signed with Yep Roc Records.

In 2005, Simmonz left the band and was replaced by Brett Whitacre. that year, Robert Plant asked the Legendary Shack Shakers to open for him on his European tour. The following year, the band opened for Marty Stewart and Travis Tritt in 2006 at the Ryman Auditorium in Nashville, Tennessee. Subsequently, the band experienced increased mainstream media attention when GEICO featured their song "CB Song" in one of their commercials, and the band's song "Swampblood" was included on the soundtrack to the HBO series True Blood, earning the band a Grammy Award nomination. 2009 saw the addition of Duane Denison, formerly of the Jesus Lizard, to the line-up. The band released their seventh studio album; AgriDustrial, on April 13, 2010 on their own Colonel Knowledge record label. The band would subsequently go on hiatus from 2010 to 2015, after which they reformed with a new line-up consisting of Wilkes on vocals, harmonica and banjo, Robertson on bass, Rod Hamdallah on guitar, and Brett Whitacre on drums, and signed with Alternative Tentacles.

In 2017, Wilkes released his first solo album, Fire Dream, and the Legendary Shack Shakers' line-up changed to Wilkes, Hamdallah and new rhythm section, bassist Fuller Condon and drummer Preston Corn, before the band recorded and released the album After You've Gone, a song cycle inspired by Wilkes' divorce. In 2019, the band performed on the PBS television series Sun Studio Sessions, and released an album of this performance under the title Live from Sun Studio. In 2020, the band planned to play in Aurora, Kentucky, but the performance was cancelled due to the COVID-19 pandemic and subsequently delayed until the following year. With a new line-up consisting of Wilkes, guitarist Gary Siperko, upright bassist Fuller Condon and drummer Preston Corn, the band released Cockadoodledeux, an album of traditional country and Western songs which includes guest appearances by seven former members of the band, as well as Alternative Tentacles founder Jello Biafra.

Musical style
Bass Frontiers wrote that Legendary Shack Shakers "have been billed as everything from rockabilly to gothic country, psychobilly and alt. country". J.D. Wilkes says that the original incarnation of the Legendary Shack Shakers focused on playing rockabilly, "hillbilly" music, Memphis blues and Western swing. Wilkes described the Legendary Shack Shakers' music as "Americana rockabilly"; Vail Daily said that the band performs a mix of blues, rock, punk rock, and country music. The Phoenix New Times said that "the southern gothic rockabilly act goes above and beyond much of those genres to throw down their captivating version of hillbilly blues-rock." The Kalamazoo Gazette described the Legendary Shack Shakers' music as "mutant Southern rock". AllMusic described the Legendary Shack Shakers as a "raucous roots rock band". According to City Beast, the band's musical style also encompasses country blues and carnival music.

Wilkes publicly disavowed the psychobilly label the band is sometimes categorized under, considering the genre's performers "all pompadour and no substance", stating of the scene, "These new bands trying to sound like the Cramps or doing the ‘hellbilly’ thing — they only pick up on the clichés of it." Wilkes took issue with the genre's fans' lack of familiarity with rockabilly artists like Charlie Feathers and dismissed psychobilly performers as "mall punk with pompadours", calling psychobilly fans "pompadork". Additionally, Wilkes "openly expressed disdain for alt-country and its musical carpetbaggers", according to The A.V. Club.

Wilkes stated regarding the band's use of the term "Southern Gothic", "I don’t think we’re Goth in the sense of veils and black clothing, people in perpetual mourning, funereal mode. [...] It’s the traditional term, rather than the trendy, Americanized, fad version of it. [...] [Southern Gothic] takes an angle that there’s something grotesque and beautiful in the traditions of the South, the backdrop of Southern living." Wilkes connects the many styles the band performs to the blues, saying that he considers rockabilly "the white man's version of blues" and klezmer to be "the Jew's blues". He described the band's performance as being "like a Pentecostal church revival, whipping them into a frenzy and getting them involved in the moment."

When Duane Denison joined the band, the Legendary Shack Shakers shifted their sound again, with Wilkes calling this new sound "agridustrial", explaining that it is "kind of chunky industrial patterns, but give it kind of a rustic feel [...] like the sounds of farm implements, that clanking cacophony of rural industry. Kind of like how Johnny Cash used a train rhythm." Since 2015, the Legendary Shack Shakers have predominantly played country music.

Wilkes cited as musical influences Little Walter, Howlin' Wolf, Tom Waits, the Louvin Brothers, Dock Boggs, James Harman and Roscoe Holcomb. Outside of musical influences, Gary Larson's The Far Side cartoon "Cow Tools" inspired the name of one of the band's introductions.

Discography

 * Studio albums
 *  J.D.'s Tasteless Chill Tonic  (Conan Records, 1996)
 *  Hunkerdown (Spinout, 1998)
 * Cockadoodledon't (Bloodshot, 2003)
 * Believe (YepRoc, 2004)
 * Pandelirium (YepRoc, 2006)
 * Swampblood (YepRoc, 2007)
 * AgriDustrial (Colonel Knowledge, 2010)
 * The Southern Surreal (Alternative Tentacles Records, 2015)
 * After You've Gone (Last Chance Records, 2017)
 * Cockadoodledeux (Alternative Tentacles, 2021)

 * Live albums
 *  Lower Broad Lo-Fi (Arkam Records, 2007)
 *  Live from Sun Studio  (Chicken Ranch Records, 2020)

Filmography

 * Seven Signs, shown at the Raindance Film Festival 2008

title: Legendary Shack Shakers


text:
Deterministic finite automaton

In the theory of computation, a branch of theoretical computer science, a deterministic finite automaton (DFA)—also known as deterministic finite acceptor (DFA), deterministic finite-state machine (DFSM), or deterministic finite-state automaton (DFSA)—is a finite-state machine that accepts or rejects a given string of symbols, by running through a state sequence uniquely determined by the string. Deterministic refers to the uniqueness of the computation run. In search of the simplest models to capture finite-state machines, Warren McCulloch and Walter Pitts were among the first researchers to introduce a concept similar to finite automata in 1943.

The figure illustrates a deterministic finite automaton using a state diagram. In this example automaton, there are three states: S0, S1, and S2 (denoted graphically by circles). The automaton takes a finite sequence of 0s and 1s as input. For each state, there is a transition arrow leading out to a next state for both 0 and 1. Upon reading a symbol, a DFA jumps deterministically from one state to another by following the transition arrow. For example, if the automaton is currently in state S0 and the current input symbol is 1, then it deterministically jumps to state S1. A DFA has a start state (denoted graphically by an arrow coming in from nowhere) where computations begin, and a set of accept states (denoted graphically by a double circle) which help define when a computation is successful.

A DFA is defined as an abstract mathematical concept, but is often implemented in hardware and software for solving various specific problems such as lexical analysis and pattern matching. For example, a DFA can model software that decides whether or not online user input such as email addresses are syntactically valid.

DFAs have been generalized to nondeterministic finite automata (NFA) which may have several arrows of the same label starting from a state. Using the powerset construction method, every NFA can be translated to a DFA that recognizes the same language. DFAs, and NFAs as well, recognize exactly the set of regular languages.

Formal definition
A deterministic finite automaton $M$ is a 5-tuple, $(Q, Σ, δ, q_{0}, F)$, consisting of
 * a finite set of states $Q$
 * a finite set of input symbols called the alphabet $Σ$
 * a transition function $δ : Q × Σ → Q$
 * an initial or start state $$q_0 \in Q$$
 * a set of accept states $$F \subseteq Q$$

Let $w = a_{1}a_{2}...a_{n}$ be a string over the alphabet $Σ$. The automaton $M$ accepts the string $w$ if a sequence of states, $r_{0}, r_{1}, ..., r_{n}$, exists in $Q$ with the following conditions:
 * 1) $r_{0} = q_{0}$, for $r_{i+1} = δ(r_{i}, a_{i+1})$
 * 2) $$r_n \in F$$.
 * 1) $$r_n \in F$$.

In words, the first condition says that the machine starts in the start state $i = 0, ..., n − 1$. The second condition says that given each character of string $w$, the machine will transition from state to state according to the transition function $δ$. The last condition says that the machine accepts $w$ if the last input of $w$ causes the machine to halt in one of the accepting states. Otherwise, it is said that the automaton rejects the string. The set of strings that $M$ accepts is the language recognized by $M$ and this language is denoted by $q_{0}$.

A deterministic finite automaton without accept states and without a starting state is known as a transition system or semiautomaton.

For more comprehensive introduction of the formal definition see automata theory.

Example
The following example is of a DFA $M$, with a binary alphabet, which requires that the input contains an even number of 0s.

$L(M)$ where
 * $M = (Q, Σ, δ, q_{0}, F)$ and
 * $δ$ is defined by the following state transition table:
 * {| border="1" cellpadding="1" cellspacing="0"
 * $Q = {S_{1}, S_{2}} |undefined$ and
 * $M$ is defined by the following state transition table:
 * {| border="1" cellpadding="1" cellspacing="0"

 * || 0 || 1
 * S1 || S2 || S1
 * S2 || S1 || S2
 * }
 * S2 || S1 || S2
 * }

The state $Σ = {0, 1}$ represents that there has been an even number of 0s in the input so far, while $q_{0} = S_{1}$ signifies an odd number. A 1 in the input does not change the state of the automaton. When the input ends, the state will show whether the input contained an even number of 0s or not. If the input did contain an even number of 0s, $M$ will finish in state $F = {S_{1}} |undefined$, an accepting state, so the input string will be accepted.

The language recognized by $n$ is the regular language given by the regular expression, where   is the Kleene star, e.g.,   denotes any number (possibly zero) of consecutive ones.

Complete and incomplete
According to the above definition, deterministic finite automata are always complete: they define from each state a transition for each input symbol.

While this is the most common definition, some authors use the term deterministic finite automaton for a slightly different notion: an automaton that defines at most one transition for each state and each input symbol; the transition function is allowed to be partial. When no transition is defined, such an automaton halts.

Local automata
A local automaton is a DFA, not necessarily complete, for which all edges with the same label lead to a single vertex. Local automata accept the class of local languages, those for which membership of a word in the language is determined by a "sliding window" of length two on the word.

A Myhill graph over an alphabet A is a directed graph with vertex set A and subsets of vertices labelled "start" and "finish". The language accepted by a Myhill graph is the set of directed paths from a start vertex to a finish vertex: the graph thus acts as an automaton. The class of languages accepted by Myhill graphs is the class of local languages.

Randomness
When the start state and accept states are ignored, a DFA of $k$ states and an alphabet of size $n$ can be seen as a digraph of $k$ vertices in which all vertices have $k$ out-arcs labeled $S_{1}$ (a $k$-out digraph). It is known that when $S_{2}$ is a fixed integer, with high probability, the largest strongly connected component (SCC) in such a $k$-out digraph chosen uniformly at random is of linear size and it can be reached by all vertices. It has also been proven that if $n$ is allowed to increase as $F$ increases, then the whole digraph has a phase transition for strong connectivity similar to Erdős–Rényi model for connectivity.

In a random DFA, the maximum number of vertices reachable from one vertex is very close to the number of vertices in the largest SCC with high probability. This is also true for the largest induced sub-digraph of minimum in-degree one, which can be seen as a directed version of $S_{1}$-core.

Closure properties
If DFAs recognize the languages that are obtained by applying an operation on the DFA recognizable languages then DFAs are said to be closed under the operation. The DFAs are closed under the following operations.

• Union

• Intersection (see picture)

• Concatenation

• Complement

• Kleene closure

• Reversal

• Quotient

• Substitution

• Homomorphism

For each operation, an optimal construction with respect to the number of states has been determined in state complexity research. Since DFAs are equivalent to nondeterministic finite automata (NFA), these closures may also be proved using closure properties of NFA.

As a transition monoid
A run of a given DFA can be seen as a sequence of compositions of a very general formulation of the transition function with itself. Here we construct that function.

For a given input symbol $$a \in \Sigma$$, one may construct a transition function $$\delta_a : Q \rightarrow Q$$ by defining $$\delta_a(q) = \delta(q,a)$$ for all $$q \in Q$$. (This trick is called currying.) From this perspective, $$\delta_a$$ "acts" on a state in Q to yield another state. One may then consider the result of function composition repeatedly applied to the various functions $$\delta_a$$, $$\delta_b$$, and so on. Given a pair of letters $$a, b \in \Sigma$$, one may define a new function $$\widehat\delta_{ab}=\delta_a \circ \delta_b$$, where $$\circ$$ denotes function composition.

Clearly, this process may be recursively continued, giving the following recursive definition of $$\widehat\delta : Q \times \Sigma^{\star} \rightarrow Q$$:
 * $$\widehat\delta ( q, \epsilon ) = q$$, where $$\epsilon$$ is the empty string and
 * $$\widehat\delta ( q, wa ) = \delta_a(\widehat\delta ( q, w ))$$, where $$ w \in \Sigma ^*, a \in \Sigma $$ and $$q \in Q$$.

$$\widehat\delta$$ is defined for all words $$w\in\Sigma^*$$. A run of the DFA is a sequence of compositions of $$\widehat\delta$$ with itself.

Repeated function composition forms a monoid. For the transition functions, this monoid is known as the transition monoid, or sometimes the transformation semigroup. The construction can also be reversed: given a $$\widehat\delta$$, one can reconstruct a $$\delta$$, and so the two descriptions are equivalent.

Advantages and disadvantages
DFAs are one of the most practical models of computation, since there is a trivial linear time, constant-space, online algorithm to simulate a DFA on a stream of input. Also, there are efficient algorithms to find a DFA recognizing:

Because DFAs can be reduced to a canonical form (minimal DFAs), there are also efficient algorithms to determine:
 * the complement of the language recognized by a given DFA.
 * the union/intersection of the languages recognized by two given DFAs.
 * whether a DFA accepts any strings (Emptiness Problem)
 * whether a DFA accepts all strings (Universality Problem)
 * whether two DFAs recognize the same language (Equality Problem)
 * whether the language recognized by a DFA is included in the language recognized by a second DFA (Inclusion Problem)
 * the DFA with a minimum number of states for a particular regular language (Minimization Problem)

DFAs are equivalent in computing power to nondeterministic finite automata (NFAs). This is because, firstly any DFA is also an NFA, so an NFA can do what a DFA can do. Also, given an NFA, using the powerset construction one can build a DFA that recognizes the same language as the NFA, although the DFA could have exponentially larger number of states than the NFA. However, even though NFAs are computationally equivalent to DFAs, the above-mentioned problems are not necessarily solved efficiently also for NFAs. The non-universality problem for NFAs is PSPACE complete since there are small NFAs with shortest rejecting word in exponential size. A DFA is universal if and only if all states are final states, but this does not hold for NFAs. The Equality, Inclusion and Minimization Problems are also PSPACE complete since they require forming the complement of an NFA which results in an exponential blow up of size.

On the other hand, finite-state automata are of strictly limited power in the languages they can recognize; many simple languages, including any problem that requires more than constant space to solve, cannot be recognized by a DFA. The classic example of a simply described language that no DFA can recognize is bracket or Dyck language, i.e., the language that consists of properly paired brackets such as word "()". Intuitively, no DFA can recognize the Dyck language because DFAs are not capable of counting: a DFA-like automaton needs to have a state to represent any possible number of "currently open" parentheses, meaning it would need an unbounded number of states. Another simpler example is the language consisting of strings of the form anbn for some finite but arbitrary number of as, followed by an equal number of bs.

DFA identification from labeled words
Given a set of positive words $$S^+ \subset \Sigma^*$$ and a set of negative words $$S^- \subset \Sigma^*$$ one can construct a DFA that accepts all words from $$S^+$$ and rejects all words from $$S^-$$: this problem is called DFA identification (synthesis, learning). While some DFA can be constructed in linear time, the problem of identifying a DFA with the minimal number of states is NP-complete. The first algorithm for minimal DFA identification has been proposed by Trakhtenbrot and Barzdin and is called the TB-algorithm. However, the TB-algorithm assumes that all words from $$\Sigma$$ up to a given length are contained in either $$S^+ \cup S^-$$.

Later, K. Lang proposed an extension of the TB-algorithm that does not use any assumptions about $$S^+$$ and $$S^-$$, the Traxbar algorithm. However, Traxbar does not guarantee the minimality of the constructed DFA. In his work E.M. Gold also proposed a heuristic algorithm for minimal DFA identification. Gold's algorithm assumes that $$S^+$$ and $$S^-$$ contain a characteristic set of the regular language; otherwise, the constructed DFA will be inconsistent either with $$S^+$$ or $$S^-$$. Other notable DFA identification algorithms include the RPNI algorithm, the Blue-Fringe evidence-driven state-merging algorithm, and Windowed-EDSM. Another research direction is the application of evolutionary algorithms: the smart state labeling evolutionary algorithm allowed to solve a modified DFA identification problem in which the training data (sets $$S^+$$ and $$S^-$$) is noisy in the sense that some words are attributed to wrong classes.

Yet another step forward is due to application of SAT solvers by Marjin J. H. Heule and S. Verwer: the minimal DFA identification problem is reduced to deciding the satisfiability of a Boolean formula. The main idea is to build an augmented prefix-tree acceptor (a trie containing all input words with corresponding labels) based on the input sets and reduce the problem of finding a DFA with $$C$$ states to coloring the tree vertices with $$C$$ states in such a way that when vertices with one color are merged to one state, the generated automaton is deterministic and complies with $$S^+$$ and $$S^-$$. Though this approach allows finding the minimal DFA, it suffers from exponential blow-up of execution time when the size of input data increases. Therefore, Heule and Verwer's initial algorithm has later been augmented with making several steps of the EDSM algorithm prior to SAT solver execution: the DFASAT algorithm. This allows reducing the search space of the problem, but leads to loss of the minimality guarantee. Another way of reducing the search space has been proposed by Ulyantsev et al. by means of new symmetry breaking predicates based on the breadth-first search algorithm: the sought DFA's states are constrained to be numbered according to the BFS algorithm launched from the initial state. This approach reduces the search space by $$C!$$ by eliminating isomorphic automata.

Read-only right-moving Turing machines
Read-only right-moving Turing machines are a particular type of Turing machine that only moves right; these are almost exactly equivalent to DFAs. The definition based on a singly infinite tape is a 7-tuple

 * $$M = \langle Q, \Gamma, b, \Sigma, \delta, q_0, F \rangle,$$

where
 * $$Q$$ is a finite set of states;
 * $$\Gamma$$ is a finite set of the tape alphabet/symbols;
 * $$b \in \Gamma$$ is the blank symbol (the only symbol allowed to occur on the tape infinitely often at any step during the computation);
 * $$\Sigma$$, a subset of $$\Gamma$$ not including b, is the set of input symbols;
 * $$\delta: Q \times \Gamma \to Q \times \Gamma \times \{R\}$$ is a function called the transition function, R is a right movement (a right shift);
 * $$q_0 \in Q$$ is the initial state;
 * $$F \subseteq Q$$ is the set of final or accepting states.

The machine always accepts a regular language. There must exist at least one element of the set ⇭⇭⇭ (a HALT state) for the language to be nonempty.

Example of a 3-state, 2-symbol read-only Turing machine

 * $$Q = \{ A, B, C, \text{HALT} \};$$
 * $$\Gamma = \{ 0, 1 \};$$
 * $$b = 0$$, "blank";
 * $$\Sigma = \varnothing$$, empty set;
 * $$\delta = $$ see state-table above;
 * $$q_0 = A$$, initial state;
 * $$F = $$ the one element set of final states: $$\{\text{HALT}\}$$.

title: Deterministic finite automaton


text:
Nondeterministic finite automaton

In automata theory, a finite-state machine is called a deterministic finite automaton (DFA), if A nondeterministic finite automaton (NFA), or nondeterministic finite-state machine, does not need to obey these restrictions. In particular, every DFA is also an NFA. Sometimes the term NFA is used in a narrower sense, referring to an NFA that is not a DFA, but not in this article.
 * each of its transitions is uniquely determined by its source state and input symbol, and
 * reading an input symbol is required for each state transition.

Using the subset construction algorithm, each NFA can be translated to an equivalent DFA; i.e., a DFA recognizing the same formal language. Like DFAs, NFAs only recognize regular languages. NFAs were introduced in 1959 by Michael O. Rabin and Dana Scott, who also showed their equivalence to DFAs. NFAs are used in the implementation of regular expressions: Thompson's construction is an algorithm for compiling a regular expression to an NFA that can efficiently perform pattern matching on strings. Conversely, Kleene's algorithm can be used to convert an NFA into a regular expression (whose size is generally exponential in the input automaton).

NFAs have been generalized in multiple ways, e.g., nondeterministic finite automata with ε-moves, finite-state transducers, pushdown automata, alternating automata, ω-automata, and probabilistic automata. Besides the DFAs, other known special cases of NFAs are unambiguous finite automata (UFA) and self-verifying finite automata (SVFA).

Informal introduction
There are two ways to describe the behavior of an NFA, and both of them are equivalent. The first way makes use of the nondeterminism in the name of an NFA. For each input symbol, the NFA transitions to a new state until all input symbols have been consumed. In each step, the automaton nondeterministically "chooses" one of the applicable transitions. If there exists at least one "lucky run", i.e. some sequence of choices leading to an accepting state after completely consuming the input, it is accepted. Otherwise, i.e. if no choice sequence at all can consume all the input and lead to an accepting state, the input is rejected.

In the second way, the NFA consumes a string of input symbols, one by one. In each step, whenever two or more transitions are applicable, it "clones" itself into appropriately many copies, each one following a different transition. If no transition is applicable, the current copy is in a dead end, and it "dies". If, after consuming the complete input, any of the copies is in an accept state, the input is accepted, else, it is rejected.

Formal definition
For a more elementary introduction of the formal definition, see automata theory.

Automaton
An NFA is represented formally by a 5-tuple, $$(Q, \Sigma, \delta, q_0, F)$$, consisting of
 * a finite set of states $$Q$$,
 * a finite set of input symbols $$\Sigma$$,
 * a transition function $$\delta$$ : $$Q\times \Sigma \rightarrow \mathcal{P}(Q)$$,
 * an initial (or start) state $$q_0 \in Q$$, and
 * a set of states $$F$$ distinguished as accepting (or final) states $$F \subseteq Q$$.

Here, $$\mathcal{P}(Q)$$ denotes the power set of $$Q$$.

Recognized language
Given an NFA $$M = (Q, \Sigma, \delta, q_0, F)$$, its recognized language is denoted by $$L(M)$$, and is defined as the set of all strings over the alphabet $$\Sigma$$ that are accepted by $$M$$.

Loosely corresponding to the above informal explanations, there are several equivalent formal definitions of a string $$w = a_1 a_2 ... a_n$$ being accepted by $$M$$:
 * $$w$$ is accepted if a sequence of states, $$r_0, r_1, ..., r_n$$, exists in $$Q$$ such that:
 * $$r_0 = q_0$$
 * $$r_{i+1} \in \delta (r_i, a_{i+1})$$, for $$i = 0, \ldots, n-1$$
 * $$r_n \in F$$.
 * In words, the first condition says that the machine starts in the start state $$q_0$$. The second condition says that given each character of string $$w$$, the machine will transition from state to state according to the transition function $$\delta$$. The last condition says that the machine accepts $$w$$ if the last input of $$w$$ causes the machine to halt in one of the accepting states. In order for $$w$$ to be accepted by $$M$$, it is not required that every state sequence ends in an accepting state, it is sufficient if one does. Otherwise, i.e. if it is impossible at all to get from $$q_0$$ to a state from $$F$$ by following $$w$$, it is said that the automaton rejects the string. The set of strings $$M$$ accepts is the language recognized by $$M$$ and this language is denoted by $$L(M)$$.

 * Alternatively, $$w$$ is accepted if $$\delta^*(q_0, w) \cap F \not = \emptyset$$, where $$\delta^*: Q \times \Sigma^* \rightarrow \mathcal{P}(Q)$$ is defined recursively by:
 * $$\delta^*(r, \epsilon) = \{r\}$$ where $$\epsilon$$ is the empty string, and
 * $$\delta^*(r, xa)= \bigcup_{r' \in \delta^*(r, x)} \delta(r', a)$$ for all $$x \in \Sigma^*, a \in \Sigma$$.
 * In words, $$\delta^*(r, x)$$ is the set of all states reachable from state $$r$$ by consuming the string $$x$$. The string $$w$$ is accepted if some accepting state in $$F$$ can be reached from the start state $$q_0$$ by consuming $$w$$.

Initial state
The above automaton definition uses a single initial state, which is not necessary. Sometimes, NFAs are defined with a set of initial states. There is an easy construction that translates an NFA with multiple initial states to an NFA with a single initial state, which provides a convenient notation.

Example
The following automaton $$M$$, with a binary alphabet, determines if the input ends with a 1. Let $$M = (\{p, q\}, \{0, 1\}, \delta, p, \{q\})$$ where the transition function $$\delta$$ can be defined by this state transition table (cf. upper left picture):
 * {| class="wikitable" style="text-align:center;"

! ! 0 ! 1 ! $$p$$ ! $$q$$ Since the set $$\delta(p,1)$$ contains more than one state, $$M$$ is nondeterministic. The language of $$M$$ can be described by the regular language given by the regular expression.
 * $$\{p\}$$
 * $$\{p,q\}$$
 * $$\emptyset$$
 * $$\emptyset$$
 * }

All possible state sequences for the input string "1011" are shown in the lower picture.

The string is accepted by $$M$$ since one state sequence satisfies the above definition; it does not matter that other sequences fail to do so. The picture can be interpreted in a couple of ways: The feasibility to read the same picture in two ways also indicates the equivalence of both above explanations.
 * In terms of the above "lucky-run" explanation, each path in the picture denotes a sequence of choices of $$M$$.
 * In terms of the "cloning" explanation, each vertical column shows all clones of $$M$$ at a given point in time, multiple arrows emanating from a node indicate cloning, a node without emanating arrows indicating the "death" of a clone.
 * Considering the first of the above formal definitions, "1011" is accepted since when reading it $$M$$ may traverse the state sequence $$\langle r_0,r_1,r_2,r_3,r_4 \rangle = \langle p, p, p, p, q \rangle$$, which satisfies conditions 1 to 3.
 * Concerning the second formal definition, bottom-up computation shows that $$\delta^*(p,\epsilon) = \{ p \}$$, hence $$\delta^*(p,1) = \delta(p,1) = \{ p,q \}$$, hence $$\delta^*(p,10) = \delta(p,0) \cup \delta(q,0) = \{ p \} \cup \{\}$$, hence $$\delta^*(p,101) = \delta(p,1) = \{ p,q \}$$, and hence $$\delta^*(p,1011) = \delta(p,1) \cup \delta(q,1) = \{ p,q \} \cup \{\}$$; since that set is not disjoint from $$\{ q \}$$, the string "1011" is accepted.

In contrast, the string "10" is rejected by $$M$$ (all possible state sequences for that input are shown in the upper right picture), since there is no way to reach the only accepting state, $$q$$, by reading the final 0 symbol. While $$q$$ can be reached after consuming the initial "1", this does not mean that the input "10" is accepted; rather, it means that an input string "1" would be accepted.

Equivalence to DFA
A deterministic finite automaton (DFA) can be seen as a special kind of NFA, in which for each state and symbol, the transition function has exactly one state. Thus, it is clear that every formal language that can be recognized by a DFA can be recognized by an NFA.

Conversely, for each NFA, there is a DFA such that it recognizes the same formal language. The DFA can be constructed using the powerset construction.

This result shows that NFAs, despite their additional flexibility, are unable to recognize languages that cannot be recognized by some DFA. It is also important in practice for converting easier-to-construct NFAs into more efficiently executable DFAs. However, if the NFA has n states, the resulting DFA may have up to 2n states, which sometimes makes the construction impractical for large NFAs.

NFA with ε-moves
Nondeterministic finite automaton with ε-moves (NFA-ε) is a further generalization to NFA. In this kind of automaton, the transition function is additionally defined on the empty string ε. A transition without consuming an input symbol is called an ε-transition and is represented in state diagrams by an arrow labeled "ε". ε-transitions provide a convenient way of modeling systems whose current states are not precisely known: i.e., if we are modeling a system and it is not clear whether the current state (after processing some input string) should be q or q', then we can add an ε-transition between these two states, thus putting the automaton in both states simultaneously.

Formal definition
An NFA-ε is represented formally by a 5-tuple, $$(Q, \Sigma, \delta, q_0, F)$$, consisting of
 * a finite set of states $$Q$$
 * a finite set of input symbols called the alphabet $$\Sigma$$
 * a transition function $$\delta : Q \times (\Sigma \cup \{\epsilon\}) \rightarrow \mathcal{P}(Q)$$
 * an initial (or start) state $$q_0 \in Q$$
 * a set of states $$F$$ distinguished as accepting (or final) states $$F \subseteq Q$$.

Here, $$\mathcal{P}(Q)$$ denotes the power set of $$Q$$ and $$\epsilon$$ denotes empty string.

ε-closure of a state or set of states
For a state $$q \in Q$$, let $$E(q)$$ denote the set of states that are reachable from $$q$$ by following ε-transitions in the transition function $$\delta$$, i.e., $$p \in E(q)$$ if there is a sequence of states $$q_1,..., q_k$$ such that
 * $$q_1 = q$$,
 * $$q_{i+1} \in \delta(q_i, \varepsilon)$$ for each $$1 \le i < k$$, and
 * $$q_k = p$$.

$$E(q)$$ is known as the epsilon closure, (also ε-closure) of $$q$$.

The ε-closure of a set $$P$$ of states of an NFA is defined as the set of states reachable from any state in $$P$$ following ε-transitions. Formally, for $$P \subseteq Q$$, define $$E(P) = \bigcup\limits_{q\in P} E(q)$$.

Extended transition function
Similar to NFA without ε-moves, the transition function $$\delta$$ of an NFA-ε can be extended to strings. Informally, $$\delta^*(q,w)$$ denotes the set of all states the automaton may have reached when starting in state $$q \in Q$$ and reading the string $$w \in \Sigma^* .$$ The function $$\delta^*: Q \times \Sigma^* \rightarrow \mathcal{P}(Q)$$ can be defined recursively as follows.
 * $$\delta^*(q,\varepsilon) = E(q)$$, for each state $$q \in Q ,$$ and where $$E$$ denotes the epsilon closure;
 * Informally: Reading the empty string may drive the automaton from state $$q$$ to any state of the epsilon closure of $$q .$$

 * $\delta^*(q,wa) = \bigcup_{r \in \delta^*(q,w)} E(\delta(r,a)) ,$ for each state $$q \in Q ,$$ each string $$w \in \Sigma^*$$ and each symbol $$a \in \Sigma .$$
 * Informally: Reading the string $$w$$ may drive the automaton from state $$q$$ to any state $$r$$ in the recursively computed set $$\delta^*(q,w)$$; after that, reading the symbol $$a$$ may drive it from $$r$$ to any state in the epsilon closure of $$\delta(r,a) .$$

The automaton is said to accept a string $$w$$ if
 * $$\delta^*(q_0,w) \cap F \neq \emptyset ,$$

that is, if reading $$w$$ may drive the automaton from its start state $$q_0$$ to some accepting state in $$F .$$

Example
Let $$M$$ be a NFA-ε, with a binary alphabet, that determines if the input contains an even number of 0s or an even number of 1s. Note that 0 occurrences is an even number of occurrences as well.

In formal notation, let $$M = (\{S_0, S_1, S_2, S_3, S_4\}, \{0, 1\}, \delta, S_0, \{S_1, S_3\})$$ where the transition relation $$\delta$$ can be defined by this state transition table: $$M$$ can be viewed as the union of two DFAs: one with states $$\{S_1, S_2\}$$ and the other with states $$\{S_3, S_4\}$$. The language of $$M$$ can be described by the regular language given by this regular expression $$(1^{*}01^{*}0)^{*} \cup (0^{*}10^{*}1)^{*}$$. We define $$M$$ using ε-moves but $$M$$ can be defined without using ε-moves.

Equivalence to NFA
To show NFA-ε is equivalent to NFA, first note that NFA is a special case of NFA-ε, so it remains to show for every NFA-ε, there exists an equivalent NFA.

Given an NFA with epsilon moves $$M = (Q, \Sigma, \delta, q_0, F) ,$$ define an NFA $$M' = (Q, \Sigma, \delta', q_0, F') ,$$ where
 * $$F' = \begin{cases} F \cup \{ q_0 \} & \text{ if } E(q_0) \cap F \neq \{\} \\ F & \text{ otherwise } \\ \end{cases} $$

and
 * $$\delta'(q,a) = \delta^*(q,a) $$ for each state $$q \in Q$$ and each symbol $$a \in \Sigma ,$$ using the extended transition function $$\delta^*$$ defined above.

One has to distinguish the transition functions of $$M$$ and $$M' ,$$ viz. $$\delta$$ and $$\delta' ,$$ and their extensions to strings, $$\delta$$ and $$\delta'^* ,$$ respectively. By construction, $$M'$$ has no ε-transitions.

One can prove that $$\delta'^*(q_0,w) = \delta^*(q_0,w)$$ for each string $$w \neq \varepsilon$$, by induction on the length of $$w .$$

Based on this, one can show that $$\delta'^*(q_0,w) \cap F' \neq \{\}$$ if, and only if, $$\delta^*(q_0,w) \cap F \neq \{\},$$ for each string $$w \in \Sigma^* :$$
 * If $$w = \varepsilon ,$$ this follows from the definition of $$F' .$$
 * Otherwise, let $$w = va$$ with $$v \in \Sigma^*$$ and $$a \in \Sigma .$$
 * From $$\delta'^*(q_0,w) = \delta^*(q_0,w)$$ and $$F \subseteq F' ,$$ we have $$\delta'^*(q_0,w) \cap F' \neq \{\} \;\Leftarrow\; \delta^*(q_0,w) \cap F \neq \{\} ;$$ we still have to show the "$$\Rightarrow$$" direction.
 * If $$\delta'^*(q_0,w)$$ contains a state in $$F' \setminus \{ q_0 \} ,$$ then $$\delta^*(q_0,w)$$ contains the same state, which lies in $$F$$.
 * If $$\delta'^*(q_0,w)$$ contains $$q_0 ,$$ and $$q_0 \in F ,$$ then $$\delta^*(q_0,w)$$ also contains a state in $$F ,$$ viz. $$q_0 .$$
 * If $$\delta'^*(q_0,w)$$ contains $$q_0 ,$$ and $$q_0 \not\in F ,$$ but $$q_0\in F',$$ then there exists a state in $$E(q_0)\cap F$$, and the same state must be in $\delta^*(q_0,w) = \bigcup_{r \in \delta^*(q,v)} E(\delta(r,a)) .$

Since NFA is equivalent to DFA, NFA-ε is also equivalent to DFA.

Closure properties

The set of languages recognized by NFAs is closed under the following operations. These closure operations are used in Thompson's construction algorithm, which constructs an NFA from any regular expression. They can also be used to prove that NFAs recognize exactly the regular languages.

 * Union (cf. picture); that is, if the language L1 is accepted by some NFA A1 and L2 by some A2, then an NFA Au can be constructed that accepts the language L1∪L2.
 * Intersection; similarly, from A1 and A2 an NFA Ai can be constructed that accepts L1∩L2.
 * Concatenation
 * Negation; similarly, from A1 an NFA An can be constructed that accepts Σ*\L1.
 * Kleene closure

Since NFAs are equivalent to nondeterministic finite automaton with ε-moves (NFA-ε), the above closures are proved using closure properties of NFA-ε.

Properties
The machine starts in the specified initial state and reads in a string of symbols from its alphabet. The automaton uses the state transition function Δ to determine the next state using the current state, and the symbol just read or the empty string. However, "the next state of an NFA depends not only on the current input event, but also on an arbitrary number of subsequent input events. Until these subsequent events occur it is not possible to determine which state the machine is in". If, when the automaton has finished reading, it is in an accepting state, the NFA is said to accept the string, otherwise it is said to reject the string.

The set of all strings accepted by an NFA is the language the NFA accepts. This language is a regular language.

For every NFA a deterministic finite automaton (DFA) can be found that accepts the same language. Therefore, it is possible to convert an existing NFA into a DFA for the purpose of implementing a (perhaps) simpler machine. This can be performed using the powerset construction, which may lead to an exponential rise in the number of necessary states. For a formal proof of the powerset construction, please see the Powerset construction article.

Implementation
There are many ways to implement a NFA:
 * Convert to the equivalent DFA. In some cases this may cause exponential blowup in the number of states.
 * Keep a set data structure of all states which the NFA might currently be in. On the consumption of an input symbol, unite the results of the transition function applied to all current states to get the set of next states; if ε-moves are allowed, include all states reachable by such a move (ε-closure). Each step requires at most s2 computations, where s is the number of states of the NFA. On the consumption of the last input symbol, if one of the current states is a final state, the machine accepts the string. A string of length n can be processed in time O(ns2), and space O(s).
 * Create multiple copies. For each n way decision, the NFA creates up to n−1 copies of the machine. Each will enter a separate state. If, upon consuming the last input symbol, at least one copy of the NFA is in the accepting state, the NFA will accept. (This, too, requires linear storage with respect to the number of NFA states, as there can be one machine for every NFA state.)
 * Explicitly propagate tokens through the transition structure of the NFA and match whenever a token reaches the final state. This is sometimes useful when the NFA should encode additional context about the events that triggered the transition. (For an implementation that uses this technique to keep track of object references have a look at Tracematches.)

Complexity

 * One can solve in linear time the emptiness problem for NFA, i.e., check whether the language of a given NFA is empty. To do this, we can simply perform a depth-first search from the initial state and check if some final state can be reached.
 * It is PSPACE-complete to test, given an NFA, whether it is universal, i.e., if there is a string that it does not accept. As a consequence, the same is true of the inclusion problem, i.e., given two NFAs, is the language of one a subset of the language of the other.
 * Given as input an NFA A and an integer n, the counting problem of determining how many words of length n are accepted by A is intractable; it is #P-hard. In fact, this problem is complete (under parsimonious reductions) for the complexity class SpanL.

Application of NFA
NFAs and DFAs are equivalent in that if a language is recognized by an NFA, it is also recognized by a DFA and vice versa. The establishment of such equivalence is important and useful. It is useful because constructing an NFA to recognize a given language is sometimes much easier than constructing a DFA for that language. It is important because NFAs can be used to reduce the complexity of the mathematical work required to establish many important properties in the theory of computation. For example, it is much easier to prove closure properties of regular languages using NFAs than DFAs.

title: Nondeterministic finite automaton


text:
Talk:Deterministic finite automaton

Technical flag
I have rewritten the intro and added the section "Accept and Generate modes", both of which aim to be a non-technical introduction. Is this sufficient to remove the technical flag? Ounsworth (talk) 18:50, 5 August 2010 (UTC)

What field?
To what field of human endeavor does this relate? Could someone put an introductory sentance in English for the rest of us? Thanks! ;) Mark Richards 06:21, 14 May 2004 (UTC)

 * Doesn't everyone know automata theory? :-)  -- jaredwf 07:27, 14 May 2004 (UTC)

Thanks Jaredwf Just a stupid question though - Finite State Machine says that it is related to 'computer science', while DFST points to 'Theory of computing'. Is this as it should be? Thanks! Mark Richards 15:39, 14 May 2004 (UTC)

 * I changed the finite state machine to say theory of computation, since theory of computation is a more exact answer.  Thanks for noticing.  -- jaredwf 15:46, 14 May 2004 (UTC)
 * Both are correct! Theory of Computation is a subdicipline of Computer Science.  —Preceding unsigned comment added by Ben 1220 (talk • contribs) 09:36, 16 September 2009 (UTC)

symbols
The symbols used to describe the 5-tuple are inconsistent with those in Automata theory. Is it better to change to $$\langle Q, \Sigma, \delta, q_0, F\rangle$$? My textbook also uses these notations.

I'm in favor of this change. Pkirlin 06:47, 11 November 2005 (UTC)

i m a student of computer science engineering and for me automata theory and formal languages is a very new subject. i m not being able to get hold of the subject properly. i cannot understand the subject. please suggest somthing. —Preceding unsigned comment added by 115.248.12.253 (talk) 06:23, 6 March 2010 (UTC)
 * agree. Me too. We should make this change. Using S conflicts with S for semigroup. Using A conflicts with A for Autamaton. Using M conflicts with M for monoid. linas 14:17, 26 April 2007 (UTC)
 * Done. I have at least two books that use this format, so I went ahead and made the change. If anyone disagrees, please comment here and let me know. Thanks! ThomasOwens (talk) 00:01, 11 December 2008 (UTC)

Merge proposal
Oppose. Other articles reference FSMs without the presumption of determinism. --Ancheta Wis 02:25, 3 December 2005 (UTC)

Regular languages in relation to FSM
Can someone please explain the following entry in the article more. Now sure what this exactly is in relation to FSM (the article on regular language is just as perplexing).

The language of M can be described by the regular language given by this regular expression:

1*(01*01*)* yusufm 20:51, 13 April 2006 (UTC)

The section on regular language is the best place to parse this. The * is the Kleene Star mentioned in that article. So 1* is the set { epsilon, 1, 11, 111, 1111...) The Kleene star operator over a number of the alphabet symbols such as (01)* is the set { epsilon, 01, 0101, 010101...) Essentially it means none, one, or more of the items repeating.

DFA search image
I've just fixed up the DFA image Image:DFA search mommy.svg so that it renders again. It's intended for string search algorithm but may be useful here. Dcoetzee 03:57, 2 April 2007 (UTC)

Missing paths - still deterministic?
The definition for DFA states that there should be one and only one transition for each pair of states and inputs. The definition for NFA only addresses the case of a single input leading to multiple, different states. What about the case where an input leads off to a "dummy state" that just loops back to itself on every input? If we just eliminate the dummy state and any inputs leading to it, does the diagram still represent a DFA? If not, is it an NFA? Or something else? Thanks, Maghnus 15:25, 29 October 2007 (UTC)

 * Ambigiuous: The description may be slightly ambiguous in that every pair of states and inputs should have exactly one transition. As I understand it, missing transitions are unacceptable for a DFA, and hence would be classes as an NFA. Pyrre (talk) 03:05, 23 December 2007 (UTC)

 * Missing paths are no big deal; the definition of what it means to run such an automaton will most likely say that if a path is missing, the automaton immediately halts (this can be simulated by adding an extra state and a new path to this state for each missing path in the original automaton). So long as there are never two paths on the same state/input pair, the automaton is deterministic. — Carl (CBM · talk) 03:21, 23 December 2007 (UTC)

 * I just added a new section to mention the difference. Rp (talk) 09:47, 11 November 2015 (UTC)

 * It should be made clear that if a path is missing, the automaton halts and rejects the string. 2600:1700:6EC0:35C0:D5F2:3A1:B655:C5F7 (talk) 22:26, 4 September 2020 (UTC)

Possible error in example
In the section "Advantages and Disadvantages", the example discribes the "bracket" language - i.e. properly paired brackets. This is not formally anbn, as stated, but "Strings whose each prefix has more or equal a's than b's" Raghunandan ma (talk) 10:18, 16 August 2011 (UTC)

You are correct. It is bad language. Let me try a fix. (Ashutosh Gupta (talk) 13:34, 16 August 2011 (UTC))

Thank you. It looks better now. Also I suggest:

DFAs are equivalent in computing power to nondeterministic finite automata (NFAs). This is because, firstly any DFA is also an NFA, so an NFA can do what a DFA can do. Also, given an NFA, one can build a DFA that recognizes the same language as the NFA, although the DFA could have exponentially larger number of states than the NFA. Raghunandan ma (talk) 06:46, 17 August 2011 (UTC)

Your suggestion is good. Please add it yourself. I also suggest to cite powerset construction page for the algorithm that translates NFA into DFA. (Ashutosh Gupta (talk) 11:30, 17 August 2011 (UTC))

Have added this. Also made some small changes in the wording for union/intersection/complement at the beginning of this section. Raghunandan ma (talk) 06:53, 18 August 2011 (UTC)

Requested move

 * The following discussion is an archived discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the move request was: Moves made, uncontested Mike Cline (talk) 15:54, 3 December 2011 (UTC)

– These are more popular names of the automata theory concepts. Even within the articles the objects are referred as (non)deterministic finite automaton. Ashutosh Gupta (talk) 15:04, 25 November 2011 (UTC)
 * Deterministic finite-state machine → Deterministic finite automaton
 * Nondeterministic finite-state machine → Nondeterministic finite automaton

 * Support per nom. —Ruud 20:37, 25 November 2011 (UTC)

 * The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

DFA cannot recognize anbn?
The article states that: "Many simple languages, including any problem that requires more than constant space to solve, cannot be recognized by a DFA. [...] Another simpler example is the language consisting of strings of the form a$n$b$n$ — some finite number of a's, followed by an equal number of b's." I don't think that is correct. Consider the following state diagram:
 * S$0$ → a → S$1$ → b → S$2$ (ab)
 * S$0$ → a → S$1$ → a → S$3$ → b → S$4$ → b → S$5$ (aabb)
 * S$0$ → a → S$1$ → a → S$3$ → a → S$6$ → b → S$7$ → b → S$8$ → b → S$9$ (aaabbb)
 * And so forth.

As long as n is limited to a specific finite number, it looks like a DFA can indeed be built for the language a$n$b$n$. Granted, it will take a large number of states (perhaps on the order of 2$n$?) to embed the counting of a's and b's, but it still seems possible. Or did I miss something in the text? — Loadmaster (talk) 17:48, 27 January 2014 (UTC)

 * The wording is intended to describe the language $$\{ a^n b^n : n \in \mathbf{N} \}$$ which has infinitely many words (indeed, exactly one of length 2n for every n≥0) and I think it does so. This is not a regular language, and cannot be recognised by a DFA.  Deltahedron (talk) 19:38, 27 January 2014 (UTC)

 * I thought so, but the wording was not clear, so I changed it (adding "arbitrary" to indicate an unbounded n). — Loadmaster (talk) 22:01, 27 January 2014 (UTC)

Removed "Accept and Generate Modes" section
I've removed the "Accept and Generate Modes" section on that grounds that it's original research by a defunct user. A search through my textbooks, university library search engine and Google didn't reveal anyone else who's talking about generate modes for DFAs. Even if that section isn't original research, we should consider whether it lends undue weight to a rarely-discussed type of DFA. Chip Wildon Forster (talk) 18:42, 31 January 2015 (UTC)

Classifiers
The description of classifiers claims that a classifier has "has more than two terminal states", which seems to imply that a DFA cannot have more than two terminal states. Should this be "more than two classes of terminal states"? A DFA can obviously have three terminal states, but just two classes (accept and reject). This is not clear from the current wording on classifiers. — Preceding unsigned comment added by 131.174.142.107 (talk) 14:16, 9 October 2019 (UTC)

Definition of local automaton
Deterministic_finite_automaton says "A local automaton is a DFA for which all edges with the same label lead to a single vertex." I suggest adding "not necessarily complete" before "DFA". If we require the DFA to be complete as specified in Deterministic_finite_automaton, then it is not true that local automata can accept all local languages.

For example, consider the local language $$A$$ consisting of all strings on $${a, b, c}$$ that do not contain $$ab$$. If $$M$$ is a complete DFA in which all edges with the same label lead to a single vertex, then $$A$$ is not the language accepted by $$M$$. Proof: Note that $$ccc \in A$$ but $$abc \notin A$$. Let $$q$$ be the state of $$M$$ such that all edges with label $$c$$ lead to $$q$$. Then $$M$$ terminates at $$q$$ with input $$abc$$ or $$ccc$$, so it either accepts both or rejects both. Therefore $$A$$ is not the language accepted by $$M$$.

I have not checked the references in this section to see how they define DFA. "Local languages and the Berry-Sethi algorithm" (at https://www.irif.fr/~jep/PDF/BerrySethi.pdf) has a proof that every local language is accepted by a local automaton (Proposition 2.1). Immediately before that, its definition of local automaton includes "not necessarily complete". 2600:1700:6EC0:35C0:D5F2:3A1:B655:C5F7 (talk) 22:12, 4 September 2020 (UTC)

 * ✅ I believe you are right. Although every DFA can be made complete by adding an "error" state, completing a local DFA will destroy locality. Also, your proof looks convincing. - Jochen Burghardt (talk) 17:10, 5 September 2020 (UTC)

Recognizing valid email addresses
The lead section mentions recognizing syntactically valid email addresses as an application for deterministic finite automata. I am not sure if this is supposed to be an in-joke: the syntax and grammar of email addresses at least as defined by the original RFC 822 is quite complex, and using DFAs (at least in the form of regular expressions) is kind of seen as an anti-pattern, at least as far as I understand it. See e.g. the discussion at Talk:Email address here on Wikipedia and the top answer to the question "How to validate an email address using a regular expression?" on Stack Overflow. – Tea2min (talk) 11:37, 4 November 2020 (UTC)

 * Ooops! I found the sentence "... decides whether or not online user input such as email addresses are valid", and just inserted "syntactically" to indicate that no automaton can check whether a specified mailbox actually exists at the provider site. I wasn't aware of the complexity of address rules at Talk:Email_address (the grammar there isn't even a regular one). I guess you suggest to replace this exmaple by a simpler one; and I agree with that. What about e.g. floating point numbers, integer numbers, or identifiers in some fixed programming language, or password rules (like "at least an upper case, a lower case letter, a digit, and a punctuation char must occur")? The available images at commons:Category:Deterministic finite state automata are not too convincing for that purpose. - Jochen Burghardt (talk) 13:03, 4 November 2020 (UTC)

 * Identifiers in C are probably a nice example since you have a small alphabet (letters, digits, underscore). Password rules ("at least an upper case, a lower case letter, a digit, and a punctuation char must occur"), while simple to describe textually, would probably already be too big. (I think you need at least 1 + 4 + 6 + 4 + 1 states?) – Tea2min (talk) 15:17, 4 November 2020 (UTC)

Section "Complete and incomplete"
> According to the above definition, deterministic finite automata are always complete: they define a transition for each state and each input symbol.

Isn't the description wrong? I understand the sentence to mean that each state must have a transition and the automaton must have a transition for each input symbol, but as far as I know, each state must have a transition for each input symbol.

My suggestion: "they define from each state a transition for each input symbol."

Sicro --- 46.223.160.111 (talk) 09:19, 24 October 2021 (UTC)

 * ✅ The old description is ok (if read as "given a state and an input symbol, a transition on them is defined"), but apparently can be misleading; your suggestion is more clear, so I changed the text. - Jochen Burghardt (talk) 16:13, 24 October 2021 (UTC)

Simplified diagram representation
It should be mentioned in this article that several transitions labeled with different input symbols leading from state A to state B can be combined into one transition to display the diagram in a simplified way. Technically, however, they are separate transitions, of course.

See at the top of page 3: https://www.cs.toronto.edu/~amir/teaching/csc236f15/materials/lec10.pdf

Sicro --- 46.223.160.163 (talk) 11:40, 28 October 2021 (UTC)

 * I agree that this should be explained somewhere. Unfortunately, diagram notation isn't explained at all in this article. Instead it links to State diagram which handles the huge amount of existing variants; thus is is not that easy to find the right place to insert your information. - Jochen Burghardt (talk) 12:29, 28 October 2021 (UTC)

title: Talk:Deterministic finite automaton