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Talk:Istanbul

FA criteria
The article needs substantial work to meet the FA criteria: better referencing (including citing the uncited content, as well as improving the quality of refs so that promotional claims are cited to independent sources), updating many sections that are out of date. There is also massive overload of images in contrary to MOS:IMAGELOC. (t · c)  buidhe  21:25, 2 November 2020 (UTC)
 * This article is semi-protected, and I have no intension editing such a page unprompted, so I give my oppinion here
 * I think an article should start with its formalities and links to other articles close to the subject.
 * I think the introduction should be:
 * Istanbul (/ˌɪstænˈbʊl/ IST-an-BUUL,[7][8] US also /ˈɪstænbʊl/ IST-an-buul; Turkish: İstanbul [isˈtanbuɫ] (About this soundlisten)), formerly known as Constantinople (previous capital of the Ottoman Empire and the Roman/Byzantine Empire and was originally Byzantium an ancient Greek city in classical antiquity, is the largest city in Turkey ...
 * because very important traces from very important past eras are available in the site (the past cities were not destroyed and there has been a continious development of it). The other eras are described in other articles and so these articles should be linked to immediatly this way.
 * After the formalities go on and put up history and other aspects of the city. The introduction should be cleaned from history things and put in a history section, becaus eof the subject it must be devided into subsections. The introduction after the first formalities should describe shortly the present city, that is an important commercial centre and large city of Turkey and Europe.
 * The article should describe the present city and the past eras should mainly be taken care of by links in the formalities and the history section (as they are supposed to be described there). However present day remains (sites, institutions and activeties) from the past history shsould be decribed in the article becauase they are turist attractions of the present and listed in subsections dependent on the era. As a turist I should be able to track the most important present sites dependent on my perspective in the present day city.

 * --Zzalpha (talk) 22:13, 7 January 2022 (UTC)
 * I would like to remove the image of 'Colomn of Constantine', 'Statue of Atatürk in Büyükada' and 'Syrian nationals in districts of Istanbul' and 'Pera Museum in Beyoglu'. I find these ones least relevant to the article. Metuboy (talk) 12:01, 16 June 2022 (UTC)

 * It's clear that you are trying to make disinformation nationalism with adding "ancient greek.." bla bla thing. It's not allowed according to any Wikipedia policies. Look at the Gdansk article for some education. Old name of the city should be remove.

78.190.2.75 (talk) 18:51, 14 February 2022 (UTC)

İstiklal Avenue's current appearance

The pavement pattern on Istiklal Avenue has recently been changed. This image from November 2023 shows the current pavement pattern.

 * and, do you still want to use this image ? I'm ok with it. had a lot of other suggestion, but they don't seem active now. Bogazicili (talk) 20:52, 20 May 2024 (UTC)

 * It's not exactly the prettiest image, but concerns raised about other images might make this the only acceptable one. Uness232 (talk) 11:31, 23 May 2024 (UTC)

The view of the Bosphorus Bridge and the modern skyline from Çamlıca Hill (2013) is outdated
The in the infobox is from 2013 and displays an outdated view of the city's modern skyline. This contains additional buildings. Many new towers will appear in the coming years.

These towers are clearly not among the timeless icons of the city. Very few of them are interesting in terms of design. Many of them will eventually be demolished and replaced by newer buildings in the future, similar to the redevelopment projects in New York, London, etc.

The Anadoluhisarı and in particular Rumelihisarı fortresses can be defined as the beginning point for the "Turkish" city of Constantinople (Istanbul). Rumelihisarı played an important role during the Turkish conquest of Constantinople in 1453. It is one of the timeless icons of the city, definitely more so than some ordinary highrise tower blocks, the kind of which you can find anywhere else in the world.

My proposal is to replace this outdated image with the historical beauty of Rumelihisarı Fortress, combined with the emerald green hills of the Bosphorus, splendid yalı houses and mansions (such as the Yusuf Ziya Pasha Mansion with its unique design, visible in this image) and the Fatih Sultan Mehmet Bridge in the background, named after the person to whom the Turks owe the privilege of owning what is arguably the world's most interesting city. Poppins Potter (talk) 17:34, 17 March 2024 (UTC)

 * I understand your concerns, and I do get that the skyline photo is very outdated, however nearly all city articles on Wikipedia use a general skyline of the city as image1:
 * Ankara doesn't use the Ankara Castle
 * NYC doesn't use- (well, they do use the Empire State, but a very panoramic image of the Empire State)
 * Berlin doesn't use the Brandenburg gate
 * London doesn't use the Big Bang
 * I think you get it. The point of Wikipedia isn't to flatter any city, its to inform the general public about it. ~ eticangaaa  ( talk ) 06:02, 18 March 2024 (UTC)
 * I am for adding the new image of 2022, and for replacing new images with old ones where possible. Our task is to inform readers about the current state of the city, not to preemptively censor the city's development in recent years. Istanbul in the last 20 years has grown enormously, often changing (and not always for the better) the ambience and scenery for which it was famous. The article on the city should reflect these changes. Alex2006 (talk) 09:22, 18 March 2024 (UTC)
 * I missed the 2022 image when reading the talk page, my apologies. ~ eticangaaa  ( talk ) 10:41, 18 March 2024 (UTC)
 * For the top image, I'd prefer this . It's from 2022 and is a valued image in Commons (there is also the cropped version). It shows more areas than this . this also looks digitally altered, the colors are weird. For İstiklal Avenue,I'd prefer this We need a night time pic Bogazicili (talk) 00:13, 19 March 2024 (UTC)
 * Also,, Istanbul is in Turkey. Why did you put Turkish in quotes here ? Bogazicili (talk) 00:18, 19 March 2024 (UTC)
 * Personally, I would not necessarily oppose being added. I do not see a problem with the old photo, and I consider it to be higher quality in terms of composition and color, but I understand the reason behind replacing it.
 * The İstiklal photo proposed by @Bogazicili is, however, of unacceptably bad quality in my opinion. Uness232 (talk) 04:32, 19 March 2024 (UTC)
 * I agree, how about this image instead? ~ eticangaaa  ( talk ) 04:59, 19 March 2024 (UTC)
 * It's better than the current İstiklal image which is almost 20 years old. It is better than the one suggested by Poppins Potter. Are you ok with this one? Bogazicili (talk) 10:30, 19 March 2024 (UTC)
 * fine with me ~ eticangaaa  ( talk ) 10:31, 19 March 2024 (UTC)
 * Actually cropped one for top image looks better. What do we think about images here User:Bogazicili/sandbox? Bogazicili (talk) 12:01, 19 March 2024 (UTC)
 * Reinstate Hagia Sophia and its okay imo. ~ eticangaaa  ( talk ) 12:30, 19 March 2024 (UTC)
 * I think we can remove Ortakoy Mosque for either Topkapi or Dolmabahce palace. ~ eticangaaa  ( talk ) 16:41, 19 March 2024 (UTC)
 * My primary concern is updating the top picture. For the rest, I'm open to suggestions. But the new top pic already shows Hagia Sophia. Bogazicili (talk) 06:22, 20 March 2024 (UTC)
 * I would select this for the top image; and this or this or this or this or this or this or this for İstiklal Avenue. Poppins Potter (talk) 07:41, 20 March 2024 (UTC)
 * I think all the photos of Istiklal Avenue you provided, except the first, are not good quality enough to be placed in the infobox, but I think we all agree on the top image. And @Bogazicili you are correct, Hagia Sophia is shown in the top pic. Still, I think Ortaköy Mosque could be replaced. ~ eticangaaa  ( talk ) 07:49, 20 March 2024 (UTC)
 * How about this ? Poppins Potter (talk) 07:53, 20 March 2024 (UTC)
 * This reminds me a bit of Paris/Vienna and this reminds me a bit of London. Poppins Potter (talk) 07:56, 20 March 2024 (UTC)
 * Simple: Because the "Turkish" history of the city began with the Anadoluhisarı and Rumelihisarı fortresses. Before, it wasn't a Turkish city. Considering the role of Rumelihisarı in the successful conquest of 1453 (Bayezid I, who had built the Anadoluhisarı, wasn't successful in his earlier siege), I thought it was a significant symbol (a starting point) for the "Turkish part" of the city's history. Poppins Potter (talk) 22:18, 20 March 2024 (UTC)

For İstiklal images, I have 2 concerns: 1) People's faces shouldn't be too visible. This is technically not a requirement in Wikipedia rules. But, this page got 27 million page views since 2007 (Popular_pages). I feel it's insensitive to put people's faces in a prominent page in the infobox without their explicit consent. 2) I'd prefer a night time image but open to a really good day time one. Bogazicili (talk) 07:59, 20 March 2024 (UTC)

 * My finalists would be Parisesque versus Londonesque Poppins Potter (talk) 08:03, 20 March 2024 (UTC)
 * No to both, people's faces are too visible if you zoom into pictures. Among your suggestions, I'm only ok with this (most people have blurry faces). This was my suggestion . I'm ok with eticangaaa's suggestion  Bogazicili (talk) 08:09, 20 March 2024 (UTC)
 * Privacy rules do not apply in public spaces such as streets, squares, etc. If someone takes a photo of you when you are walking at a street, you legally don't have any privacy reservations (you can't complain about it). But if someone takes a photo of you while you are inside your home, or inside your garden, without your permission, you may sue the photographer. Poppins Potter (talk) 08:13, 20 March 2024 (UTC)
 * I agree with Bogazicili, he mentioned that it isn't in Wikipedia rules nor is it a law, yet it is insensitive and it's really not that common to use photos with peoples faces in wikipedia, especially not in the infobox of an article that gets 5000+ views daily. ~ eticangaaa  ( talk ) 08:22, 20 March 2024 (UTC)
 * Bondinho de Istanbul (2893156868).jpg that operates between Taksim Square at north and Tünel Square at the southern end of Istiklal Avenue. The Hagia Triada Church is visible in the background.]]
 * If your preference is to keep the nostalgic tram, I think this image is perfect, and it doesn't reveal the face of any person. Poppins Potter (talk) 20:52, 20 March 2024 (UTC)
 * Beyoğlu Tramvay Mayıs 2023.jpg Poppins Potter (talk) 21:00, 20 March 2024 (UTC)

Given the agreement with the top pic, I changed it. As I mentioned in above sections: "I checked Level 3 vital articles for cities, Vital_articles. There are no FA ones, but there are Good Articles: Mumbai, London, and Paris. They all use 1-3-2-1 format in the infobox (top and bottom large image, 3 images in second row, 2 images in 3rd row)." So we can also switch to 1-3-2-1 format. We can replace the Hagia Sophia picture with something else. What do you guys think of this pic ? It'd look like this: User:Bogazicili/sandbox Bogazicili (talk) 08:52, 20 March 2024 (UTC)

 * And here's an alternative with . It'd look like this User:Bogazicili/sandbox3. The bottom pic can be cropped to be more wide. Bogazicili (talk) 09:15, 20 March 2024 (UTC)
 * What do you think of this? User:Eticangaaa/istanbul ~ eticangaaa  ( talk ) 11:32, 20 March 2024 (UTC)
 * Basilica Cistern is a good suggestion! But now you have 3 pre-Ottoman historical sites in your second row. I think we can add Topkapı Palace, it's not visible in the top image. This is a quality image in Commons. This  is also from 2012. How about this User:Bogazicili/sandbox3? Bogazicili (talk) 15:18, 20 March 2024 (UTC)
 * I edited your talk page, (hope you dont mind, lol), what do you think of that layout? ~ eticangaaa  ( talk ) 11:56, 21 March 2024 (UTC)
 * No, I don't mind. I'm fine with the proposed images. My priority are top and bottom images. You prefer Maiden's Tower to Ortaköy Mosque? Ortaköy Mosque has Ottoman Baroque architecture., I'm ok with this . At least only 2 people are visible. Or something like this with blurry faces . But I'm also ok with eticangaaa's suggestion . This is from 2008, so it's a definite no. Bogazicili (talk) 15:41, 21 March 2024 (UTC)
 * Ortaköy Mosque is barely visible in the bottom image btw. Instead of Basilica Cistern, we could also consider Galata Tower Bogazicili (talk) 15:48, 21 March 2024 (UTC)
 * Galatasaray Square and Istıklal Avenue during a curfew.jpg Poppins Potter (talk) 21:31, 21 March 2024 (UTC)
 * , this image got deleted due to copyright violation. What do you think of this User:Bogazicili/sandbox3? İstiklal image is too wide for the second row and will need to be cropped (we can crop from the right). Bogazicili (talk) 19:07, 24 March 2024 (UTC)
 * , what do you think of the images here User:Bogazicili/sandbox3? (İstiklal image will need to be cropped as it's too wide) Bogazicili (talk) 05:42, 26 March 2024 (UTC)
 * @Bogazicili Jumping in here; as I still think we are moving way too fast for consensus to form, I do not have the time to argue in favor of or against every change. I will say, however, that I strongly oppose that specific FSM bridge photo. It is of poor quality, especially color-wise. Uness232 (talk) 06:04, 26 March 2024 (UTC)
 * Well, given the sad incidents in recent years, maybe it's better to keep the current image of Istiklal Avenue with the policeman, also as a warning to potential troublemakers that the area is well-protected. Poppins Potter (talk) 13:10, 30 March 2024 (UTC)
 * [[File:Istanbulun istiklali için birazda roma belki viyana esintileri görüntüleri ne güzel olur, by ismail soytekinoğlu - panoramio.jpg|thumb|This is the original image, with an improper file name and improper caption.]] Poppins Potter (talk) 14:00, 30 March 2024 (UTC)
 * Bondinho_de_Istanbul_(2893156868).jpg]]
 * There's a beautiful image of Istiklal Avenue in the "Leisure and entertainment" section of the article, but there isn't a single image of Taksim Square. Perhaps this image of Taksim Square with the nostalgic tram may be a good substitute. Poppins Potter (talk) 14:37, 30 March 2024 (UTC)
 * Maybe this image of Istiklal Avenue can be fine tuned with Photoshop and reuploaded to Wikimedia Commons with a better file name and file caption. Poppins Potter (talk) 14:41, 30 March 2024 (UTC)
 * View of Istiklal Avenue from the entrance of Galatasaray High School.jpg
 * I fine tuned the image with Photoshop, gave it an appropriate file name, and fixed the caption. Poppins Potter (talk) 15:26, 30 March 2024 (UTC)
 * @Poppins Potter I would prefer the Taksim Square photo you proposed. The one you ended up editing into the article looks completely artificial color-wise. Uness232 (talk) 15:39, 30 March 2024 (UTC)
 * I adjusted the brightness, saturation and contrast and reuploaded the file. Poppins Potter (talk) 15:52, 30 March 2024 (UTC)
 * @Poppins Potter I am not sure that fixed the fundamental issue, which exists especially on the left side of the photo, and might not be easily fixable. Uness232 (talk) 16:18, 30 March 2024 (UTC)
 * That's the light of the Sun during the early morning hours. It also exists in the original image. I reduced the color saturation and now it looks good. The details on the building facades are now much clearer compared to the original file. Poppins Potter (talk) 17:16, 30 March 2024 (UTC)
 * @Poppins Potter I am still not convinced of the quality of that image; I think it has to do with the exposure of the camera when it was being taken. I'd still prefer the Taksim Square photo you proposed. Uness232 (talk) 21:34, 30 March 2024 (UTC)
 * This one is from 2008, so no. Bogazicili (talk) 20:41, 1 April 2024 (UTC)
 * The current image is from 2007. Poppins Potter (talk) 12:47, 6 April 2024 (UTC)

What do you think about this instead? It's not perfect by any means, but it might be a good compromise. Uness232 (talk) 21:35, 5 April 2024 (UTC)

 * lovely pic - support using it here Chidgk1 (talk) 06:07, 6 April 2024 (UTC)
 * Too dark, and the surrounding buildings don't look like İstiklal Avenue at all. It looks like an ordinary street in a small Anatolian town. I would prefer maintaining the current image. Poppins Potter (talk) 12:50, 6 April 2024 (UTC)
 * What makes Istiklal Avenue special is its grand historic buildings, not the nostalgic tram installed in the early 1990s. You are concentrating on the wrong detail. Poppins Potter (talk) 12:58, 6 April 2024 (UTC)
 * @Poppins Potter I do not have any real insistence on the tram; my concerns are mostly photo quality. Uness232 (talk) 14:43, 6 April 2024 (UTC)
 * Just an fyi: I dipped out of this discussion because the multiple threads got too complicated for my little mind to handle. If it makes any difference, still i think it should be this. ~ eticangaaa  ( talk ) 18:20, 7 April 2024 (UTC)
 * How about any of these?

— Preceding unsigned comment added by Poppins Potter (talk • contribs) 18:28, 6 April 2024 (UTC)

— Preceding unsigned comment added by Poppins Potter (talk • contribs) 18:34, 6 April 2024 (UTC)

Poppins Potter (talk) 18:16, 6 April 2024 (UTC)

 * I think this one is good, but this one remains the best overall. This or this are the other logical alternatives. Poppins Potter (talk) 19:36, 6 April 2024 (UTC)
 * I prefer images where faces are blurry like this or the empty one  Bogazicili (talk) 18:14, 7 April 2024 (UTC)
 * The "empty one" was taken during a curfew (sokağa çıkma yasağı), which is the only time you can find İstiklal Avenue so empty. The curfew was probably due to COVID-19, but people may think other things (e.g. civil unrest due to political instability, a terrorist attack, etc.) so I don't think it's a good idea. It also doesn't reflect the true nature (crowded and busy) of İstiklal Avenue. The other image is too dark, I prefer daylight. Poppins Potter (talk) 15:10, 8 April 2024 (UTC)
 * İzahatli Maarif Takvimi: Curfew was actually the joke: "If you want an image of İstiklal Avenue without faces, you need a curfew." Poppins Potter (talk) 15:51, 8 April 2024 (UTC)
 * I was ok with the empty one because it was your own suggestion. I'm ok with this too . Or anything from this set where all faces are blurry  (more images here )
 * We also need to change the Hagia Sophia image since it's already in the top image. Bogazicili (talk) 16:35, 8 April 2024 (UTC)
 * There doesn't seem to be any response to this., do you object to 1-3-2-1 format used in Good Articles such as Mumbai, London, and Paris? Bogazicili (talk) 20:45, 25 April 2024 (UTC)
 * , we need you around too! Bogazicili (talk) 20:47, 25 April 2024 (UTC)
 * ugh yea you're right my apologies, i've just been busy due to school as of late (which is ironic because i usually do this while i have free time at school ~ eticangaaa  ( talk ) 05:19, 26 April 2024 (UTC)
 * @Bogazicili I think we need to start things over and talk it out one image at a time to come to a meaningful consensus, and that would mean that on practical grounds I oppose a change to the format unless enough photos are changed. Uness232 (talk) 03:50, 26 April 2024 (UTC)
 * I agree, this thread is super messed up, it would be impossible for a newcomer to come to any consensus as there are so many branches ~ eticangaaa  ( talk ) 11:55, 29 April 2024 (UTC)
 * , we are already going one image at a time? Not sure what you mean by "start things over". and, currently we need to replace the Hagia Sophia image because Hagia Sophia is repeated twice (both in top image and has its own image). Per Manual of Style/Images, we need to aim for variety. We should also aim to show Istanbul adequately. That's why I'm suggesting replacing Hagia Sopia image with a wide image which would show a larger area. Bogazicili (talk) 14:49, 3 May 2024 (UTC)
 * @Bogazicili We are not going one image at a time; that would involve different subsections and different discussions for each photo in those subsections. We are, as of now, a few editors trying to achieve consensus on this highly visible page, and we have a "structure" that no previously uninvolved editor can understand. Uness232 (talk) 14:56, 3 May 2024 (UTC)
 * I am going one image at a time, but the talk page can be restructured. I'm closing this subsection, as I believe we have achieved consensus on top image, which was already changed? Is that correct? Bogazicili (talk) 15:04, 3 May 2024 (UTC)
 * ,, and , do we have any objections to the current top image ? I think it has been stable for some time. Bogazicili (talk) 15:13, 3 May 2024 (UTC)
 * Some of the lighting on the far plane is quite overexposed/oversaturated, but it's fine. As long as we do not come across a better photo of the historical peninsula, I do not see a need for it to be changed. Uness232 (talk) 00:37, 4 May 2024 (UTC)
 * Honestly, that is the photo i contest the least. I think it is very fitting, more than the bridge. ~ eticangaaa  ( talk ) 07:37, 4 May 2024 (UTC)
 * Istiklal Avenue @ Istanbul (8321476728).jpg Poppins Potter (talk) 23:33, 10 June 2024 (UTC)
 * That photo has faces that are far too clear. Reverting for now, we can discuss and come to a new consensus as necessary. Uness232 (talk) 00:13, 11 June 2024 (UTC)
 * At least it looks like "Istiklal Avenue" and not a dark, ordinary street in a small town (the current image). Poppins Potter (talk) 00:25, 11 June 2024 (UTC)
 * If you are seeking absolute perfection, it doesn't exist. Poppins Potter (talk) 00:31, 11 June 2024 (UTC)
 * This is not about absolute perfection. We just reached a consensus about the earlier set of photos, and part of the discussion was about the clarity of faces. Discuss first; if this image is favored by others involved here, I am perfectly willing to concede. But for now, WP:QUO stays. Uness232 (talk) 00:43, 11 June 2024 (UTC)
 * Why is having "faces" in a photo so bad? Who came up with this absurd fixation? In public places, there is no privacy. Only in private places (owned by a person) you can complain if someone takes your photo without your permission. This is taught in all schools of media and journalism. Poppins Potter (talk) 00:53, 11 June 2024 (UTC)
 * Both @Bogazicili and @Eticangaaa argued that having visible faces in the infobox of a highly visible page is problematic. It's not about whether someone can legally complain. It's a preference; to avoid such photos out of sensitivity. Uness232 (talk) 12:25, 11 June 2024 (UTC)
 * I like the vibe in the current pic. But I'm ok with something like this too . It's from 2023 Bogazicili (talk) 13:25, 11 June 2024 (UTC)

The current picture in the infobox gives the impression of a "dark and insufficiently lit, unimpressive and dull street flanked by small ordinary buildings, in a small town". It's one of the worst and most unfair pictures of Istiklal Avenue I have ever seen - as if you want people to avoid the place. Poppins Potter (talk) 21:42, 11 June 2024 (UTC)
 * Besides, what makes you think that the people who appear in the photo that I shared would be disturbed to be among the "faces of Istanbul"? I'm sure many of them would feel proud and happy about it. It's no different than being selected among the "faces of Paris" or "faces of London". "You" are being unnecessarily disturbed, not "them". Don't make decisions on behalf of other people. Poppins Potter (talk) 21:48, 11 June 2024 (UTC)

 * I think you should take your own sentence into account, Poppins Potter. Just because you would be honored, and others might be as well, because we're nerds who argue over images in Wikipedia infoboxes, but others may be offended. Additionally, you were not present in the later discussions before we finalized the infobox images for the time being. It is aesthetically not pleasing to have visible people in the infobox of an article as browsed and as relevant as Istanbul, maybe fine for smaller articles, but with so many images available, it is quite silly to opt in for a bad quality one, just because it shows a more "modern" version of the street. That is all. ~ eticangaaa  ( talk ) 11:41, 12 June 2024 (UTC)
 * Am I the only person who thinks that the "dark and dull image" doesn't look like İstiklal Avenue at all? It looks more like one of its side streets, but not the avenue itself. Poppins Potter (talk) 22:10, 12 June 2024 (UTC)

Hagia Sophia image
and, currently we need to replace the Hagia Sophia image because Hagia Sophia is repeated twice (both in top image and has its own image). Per Manual of Style/Images, we need to aim for variety. We should also aim to show Istanbul adequately. That's why I'm suggesting replacing Hagia Sopia image with a wide image which would show a larger area. Bogazicili (talk) 15:09, 3 May 2024 (UTC)
 * and, what do you guys think of this image as a wide image to replace Hagia Sophia image? . It'd look like this User:Bogazicili/sandbox. It shows Bosporus and 2 bridges and Ortaköy Mosque. Bogazicili (talk) 20:46, 20 May 2024 (UTC)
 * Aye. It is recent and of high quality. I'm perfectly fine with it. ~ eticangaaa  ( talk ) 10:42, 21 May 2024 (UTC)
 * Fine by me; it's a nice photo. We would have to think of a caption, however. Uness232 (talk) 11:00, 23 May 2024 (UTC)
 * Great, after the above changes, the infobox would be like this: . I might have to resize the bottom pic a bit though, it may be too wide. Now that Ortaköy Mosque is in the bottom pic, I'm going to suggest changing it below. Bogazicili (talk) 23:05, 23 May 2024 (UTC)

Ortaköy Mosque
and, can we change this with an image for Topkapı Palace? The infobox would look like this: User:Bogazicili/sandbox Any other suggestions? Bogazicili (talk) 23:08, 23 May 2024 (UTC)

 * Or should this be replaced with Basilica Cistern, while retaining Maiden's Tower and Galata Tower? This is what it would look like (I changed Galata with a Quality Image in Commons) . If we change Ortaköy Mosque with Topkapı, we can also change either Maiden's Tower or Galata Tower with Basilica Cistern. Bogazicili (talk) 23:22, 23 May 2024 (UTC)
 * Galata tower is nice, however i am unsure about the Basilica cistern, maybe its my weird way of thought, but the color palette doesn't quite match nicely ~ eticangaaa  ( talk ) 07:30, 24 May 2024 (UTC)
 * How about this: User:Bogazicili/sandbox4? This one is a Commons quality image too, so we would improve the quality of infobox images with new Topkapı and Galata Tower images Bogazicili (talk) 18:52, 24 May 2024 (UTC)
 * I'm on board with this palette. ~ eticangaaa  ( talk ) 10:22, 26 May 2024 (UTC)
 * and, I have changed the 2 images we agreed. , can you comment on these 2 additional changes: User:Bogazicili/sandbox4? Bogazicili (talk) 17:59, 2 June 2024 (UTC)
 * Looks nice to me. I like the measured variety of color. Uness232 (talk) 23:08, 2 June 2024 (UTC)
 * Amazing! Changes have been made. Bogazicili (talk) 06:52, 3 June 2024 (UTC)
 * Whew, finally! Thank you all for your efforts, happy editing! ~ eticangaaa  ( talk ) 09:59, 3 June 2024 (UTC)

Flora and Fauna
Coyotes do not appear anywhere in Turkey. I am unable to edit to remove coyote from the list of mammals in Istanbul, so thought I would bring it to the attention of someone who can. No idea about the other animals cited, but I guess I am suspicious now. 134.243.253.241 (talk) 18:20, 10 April 2024 (UTC)

 * I deleted the whole paragraph as Daily Sabah is not a reliable source. I suspect there was a mistranslation of whatever Esra Dağlı said in Turkish. If anyone has a reliable source they could put some animals back in Chidgk1 (talk) 19:56, 10 April 2024 (UTC)
 * Why is Daily Sabah not considered a reliable source for you? I understand the fact that they are very pro-Erdoğan but that article had nothing to do with politics? ~ eticangaaa  ( talk ) 12:00, 29 April 2024 (UTC)
 * After the discussion at Reliable sources/Noticeboard/Archive 321 an example of a wildlife problem (cannot find the discussion offhand but could probably dig it out if you need it) was a mistranslation of ‘’kızılçam’’ as “red pine” which misled me into making a stupid link to an American tree article whereas it should have been Turkish pine. Are you able to find what Esra Dağlı actually said - presumably she gave the interview in Turkish? Chidgk1 (talk) 15:45, 29 April 2024 (UTC)

Edit request
Grammar. First sentence "Istanbul, is" -> "Istanbul is" there doesn't need to be a comma there. 104.232.119.107 (talk) 01:56, 12 June 2024 (UTC)
 * ✅ Tollens (talk) 02:43, 12 June 2024 (UTC)

İstiklal Avenue photo, again
@Poppins Potter has been making some undiscussed changes about the İstiklal Avenue photo and making new claims to back these changes up. @Bogazicili, @Eticangaaa (pinging as they were active in the previous discussion) and others; do you prefer photo belonging to the previously stable version, or  as of now? Uness232 (talk) 21:55, 17 June 2024 (UTC)

 * i'm so tired of this discussion.. i think the previous image was way better but if poppins potter is going to act like a fool, not participate in debates, and then continue to edit wikipedia pages to his likings after said debate has already been concluded, then he is free to do so. ~ eticangaaa  ( talk ) 22:39, 18 June 2024 (UTC)

Poppins Potter blocked as sockpuppet
His comments should not be used for consensus. Shadow4dark (talk) 23:48, 18 June 2024 (UTC)

 * You may like Moxy 🍁 00:37, 19 June 2024 (UTC)
 * thank fuck... i knew that guy couldn't have been a standalone account ~ eticangaaa  ( talk ) 09:09, 19 June 2024 (UTC)

title: Talk:Istanbul


text:
Talk:Irish Republican Army (1919–1922)

Previous discussions

 * Archive 1 (start to end 2004):
 * Archive 2 (start 2005 to August 2005, excluding discussions of current reorganisation):
 * Archive 3 (from 27 July 2005, excluding discussions of current reorganisation):
 * The House of Hohenzollern, Everybody uses the same (Irish) name...? ,

 * Archive 4 (Reorganisation discussion, from 18 July 2005):
 * Complete rewrite, IRA ceasing to exist after Civil War, IRA 1922 - 1969

 * Archive 5 (Reorganisation discussion continued, from 29 July):
 * Organisation of wikipedia coverage of IRA(s), Proposals for moving this article forward, Interim proposal,

 * Archive 6 (Reorganisation discussion continued, from 1 August):
 * Request for Comments, New proposals

 * Archive 7 (Various discussions from 1 June 2007 - 1 October 2011)

Bi-ist article
This article has appeared to have been composed by a user with what obviously is a very pro-IRA stance. For the sake of everyone's education and perhaps not unbelievable selfish smug, enlighten us Wikipedia users more about "IRA". (60.234.214.63 (talk) 23:32, 22 February 2013 (UTC)) -- TheGreatCornholio

 * What do you have in mind? This article is about the original Irish Republican Army that fought in the Irish War of Independence with the authority of Dáil Éireann.. It is heavily supported by citations of reliable external sources and is the work of many editors.
 * Or do you have in mind one of the modern organisations that subsequently took the name? If so, see List of IRAs where you might find the one you want. --Red King (talk) 20:44, 26 February 2013 (UTC)

What I naturally had in mind understandably was a complete history of any Irish Republican Army activity. The most defeatest thing they could have done was surrender and they did yet there are still some of us who are strong enough to continue. So that is my answer to you for cutting the mustard like that boy-o. I don't mean to boast or threaten you but I very well have family in Sinn Fein and I feel very proud to know that. But for the sake of education, you can't continue to be bi-ist like that with an article, because this is Wikipedia. — Preceding unsigned comment added by 60.234.214.63 (talk) 05:35, 11 May 2013 (UTC)

References inline and otherwise
As time permits I am attempting to clean the references up without changing content. Anough for today. Juan Riley (talk) 01:41, 13 June 2014 (UTC) And I have not gotten back to this reference clean up yet. Sigh. Juan Riley (talk) 00:29, 31 July 2014 (UTC)

Dates and leading caveats
Since the parenthetical statement at lead indicates that this about organization that fought in the Easter rebellion and the Anglo-Irish war..should not the info box date be 1916-1922? Juan Riley (talk) 00:29, 31 July 2014 (UTC)
 * A slight misreading Juan, the IRB and Irish Volunteers, the precossors faught in the Easter Rising ("It was descended from the Irish Volunteers, an organisation established on 25 November 1913 that staged the Easter Rising in April 1916" in the lead). In the section "Emergence of the IRA after the Easter Rising", it states "first steps towards reorganising the defeated Irish Volunteers were taken on 27 October 1917 when a convention took place in Dublin". A point being, you could put forward 1919 either as the army of the Irish Republic and the first Dail. Murry1975 (talk) 00:59, 31 July 2014 (UTC)
 * I do understand all the subtleties..however the article starts off with :This article is about the historical organisation that fought in the Easter Rising of 1916 and the Irish War of Independence of 1919–21. Juan Riley (talk) 01:14, 31 July 2014 (UTC)
 * Good spot, removed inaccuaracy. Murry1975 (talk) 01:20, 31 July 2014 (UTC)
 * If consistently followed in article...I now agree with..say 1919? Juan Riley (talk) 01:23, 31 July 2014 (UTC)
 * Give me a couple of days and I should be able to come up with the goods. Sound? Murry1975 (talk) 01:26, 31 July 2014 (UTC)
 * Sounds good to me. Juan Riley (talk) 01:28, 31 July 2014 (UTC)

Requested move 6 April 2015

 * The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: Move. We have clear consensus that this article (the pre-1922 IRA) is not the PRIMARYTOPIC of the term, and that the base name should be a WP:CONCEPTDAB for all IRA articles. There is some question as to whether Irish Republican Army (1917–22) is the best way to disambiguate the article, so if a better solution is identified, a new RM discussion can be opened without prejudice. Cúchullain t/ c 15:25, 6 May 2015 (UTC)

– The name "Irish Republican Army" is just as commonly used to refer to other groups (such as the Irish Republican Army (1922–69) and the Provisional Irish Republican Army, amongst others). There should be greater distinction between them. Charles Essie (talk) 01:23, 6 April 2015 (UTC)
 * Irish Republican Army → Irish Republican Army (1917–22)
 * List of organisations known as the Irish Republican Army → Irish Republican Army
 * Support. Googling suggests that the current (post-1969) incarnation is the one readers are seeking. The eigenvector (talk) 06:19, 6 April 2015 (UTC)  !vote by sock of community-banned user struck. Srnec (talk) 13:21, 4 May 2015 (UTC)
 * Alternative It is definitely not the WP:PRIMARYTOPIC and so should be moved, but not to the suggested target name.
 * The current name reflects the official view of later Irish states that only the pre-Treaty IRA is legally or morally entitled to call itself such, and any later IRA is merely "an unlawful organisation styling itself the Irish Republican Army". That view may be in some sense official, but
 * Wikipedia goes by common-name, not official-name and
 * it is POV: it was obviously not the later-IRA view; neither was it the UK view, in which the pre-1922 IRA was just as illegal as the later ones.
 * However, 1917 is not an appropriate start date; the IRA's origin from the Irish Volunteers was not a single event occurring in 1917 but rather an evolution from 1916 to 1921. I also think the use of a parenthetical in both the proposed rename and Irish Republican Army (1922–69) is question-begging, implying that they are two separate entities that happen to have the same name, rather than two phases in the history of a single organisation.
 * I suggest instead History of the Irish Republican Army to 1922 and History of the Irish Republican Army, 1922–69. (Or similar: I'm not sure what the naming convention is for specifying dates in such cases.)
 * Another alternative is Old IRA, which currently redirects to the pre-1922 article; however, "Old IRA" is itself an ambiguous and contested term. jnestorius(talk) 09:26, 7 April 2015 (UTC)
 * Oppose. It ain't broke. It is not hard to find what you're looking for, but it is hard to know exactly what people are looking for. Therefore leave it as is. Srnec (talk) 13:41, 7 April 2015 (UTC)
 * Nowadays, they have these amazing thingees called "search engines," including Google, Yahoo, and Bing. These sites bring up results that were popular with previous users who typed in the same or similar search terms. The eigenvector (talk) 13:45, 9 April 2015 (UTC) !vote by sock of community-banned user struck. Srnec (talk) 13:21, 4 May 2015 (UTC)
 * This page is atop my Google search. And my Duckduckgo search. "List of organisations known as the Irish Republican Army" is not in the top 10 of either. My comment was correct: it is not easy to know if people are primarily interested in the Provisional IRA, the 1922–69 IRA or an overview of them all. What search engines do show, it seems, is that, as I said, nobody has any trouble getting to the Wikipedia result they want. Srnec (talk) 22:16, 9 April 2015 (UTC)
 * Oh my. Surely you realize that this article is on top only because it is our primary topic article. The other results that come up refer to the modern IRA. The eigenvector (talk) 06:38, 10 April 2015 (UTC) !vote by sock of community-banned user struck. Srnec (talk) 13:21, 4 May 2015 (UTC)
 * I surely do. Does any of this have a point? You said that search engines will show us what people want. They show that this article is what people want most of all! When they search for "irish republican army", anyway. It shows that our List of organisations known as the Irish Republican Army is not what they want. And of course the other results are for the post-1922 IRAs. There are no other IRAs they could be for! The fact that our articles on the other IRAs come up immediately after this one in Google searches buttresses my point that nobody is having trouble getting what they want. Srnec (talk) 11:37, 10 April 2015 (UTC)
 * It seems that some clever search engine optimization has pushed this article to the top. We should all feel proud, I guess. My original recommendation above was to google . When I do that, the top result is a Britannica article that covers the history from 1919 to today. For the most part, the following results focus on post-1922 history. The eigenvector (talk) 03:26, 11 April 2015 (UTC) !vote by sock of community-banned user struck. Srnec (talk) 13:21, 4 May 2015 (UTC)
 * "it is not easy to know if people are primarily interested in the Provisional IRA, the 1922–69 IRA or an overview of them all." -- agreed, but we can add the pre-1922 IRA to that list. Hence the move request. jnestorius(talk) 09:53, 11 April 2015 (UTC)
 * If List of organisations known as the Irish Republican Army were turned into a good article (and not a list), I would support the multi-move as requested. Right now, I prefer the current layout with the hatnote to forcing folks to read the opening of the List article. I would have no problem beefing up the hatnote on this article to explicitly link to the PIRA etc. Srnec (talk) 16:24, 11 April 2015 (UTC)
 * With more than 10 percent of readers (6077/59588) taking the hat note, the current setup is definitely creating some confusion and dissatisfaction. With a hat note as long and involved as this one, I suspect plenty of readers are simply pressing the backup key on their browsers. The eigenvector (talk) 05:13, 12 April 2015 (UTC) !vote by sock of community-banned user struck. Srnec (talk) 13:21, 4 May 2015 (UTC)
 * Strong Support. The term IRA is commonly used as an umbrella term for the many factions by the layman reader . If anything List of organisations known as the Irish Republican Army should be moved to Irish Republican Army. Zarcadia (talk) 17:12, 7 April 2015 (UTC)
 * Support both moves as proposed or another alternative (such as one of User:Jnestorius's proposals above) that makes the current CONCEPTDAB page the target of "Irish Republican Army". The "old" IRA is not the primary topic, i.e. it is not "highly likely—much more likely than any other topic, and more likely than all the other topics combined—to be the topic sought when a reader searches for that term" (my emphasis). —  AjaxSmack   03:39, 11 April 2015 (UTC)
 * Support per nom. Also, there is already Category:Irish Republican Army (1917–22) members. Snappy (talk) 09:52, 13 April 2015 (UTC)
 * Support. Juan Riley (talk) 22:21, 5 May 2015 (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 or in a move review. No further edits should be made to this section.

In trying to sort out incoming links, it isn't always obvious which links should go to Irish Republican Army (1917–22) and which should stay at the concept disambiguation Irish Republican Army. Unfortunately, readers better versed in the nuances than I am will have to take on that task.--Cúchullain t/ c 15:55, 6 May 2015 (UTC)

Cut-and-paste
The bulk of two sections of this article properly belonged in the Irish Volunteers article, as they dealt in depth with developments in the Volunteers before they became known as the IRA. I have moved the content to there as a straight cut-and-paste, replacing it with a summary section in this article. Scolaire (talk) 13:21, 15 September 2015 (UTC)

Recent edit war
I missed the recent edit war between and. What I find extraordinary is that both parties used angry edit summaries saying "take it to talk", yet neither made any attempt to discuss the edits on the talk page. Does either of you know what "take it to talk" means? For what it's worth, the IRA was the Irish Volunteers, and the two names were used interchangeably throughout the revolutionary period. They were even referred to as the Volunteers in the Treaty debates, and in anti-Treaty literature during the Civil War. For that reason, I am reverting to Alfie Gandon's edit, but I advise both of you to make proper use of talk pages in future, and to seek opinions from third parties if you can't reach agreement. Scolaire (talk) 13:00, 15 March 2017 (UTC)
 * Sorry but personal editor opinions dont matter. All cited sources say the IRA was founded in 1919. The IRA (as referred to during the rising) referred to something different.Apollo The Logician (talk) 16:11, 15 March 2017 (UTC)

 * All the cited sources? Which ones are they? Encyclopaedia Britannica? Here, here, here, here and here are just five random books thrown up by a Google Books search, and they all say what every serious student of the period knows: that the Irish Volunteers became known as the IRA during the war of Independence. That's why I suggested you use the talk page instead of edit-warring based on your own "personal editor opinions". Scolaire (talk) 09:20, 16 March 2017 (UTC)

Black and Tan uniform
(Because of Shortages) Perhaps a citation is required. I find it hard to believe in the immediate aftermath of World War 1 with hundreds of thousands of men demobbeed and the expected continuation of the war into 1919 keeping production running right up to armistice day, the war department would have enough uniforms to last into the 1930's. In basic training in 1976 we were still using the 1938 pattern webbing that was thrown away at Dunkirk. In deployment in Germany we were still using the Bren gun as our company Light Machine guns in support units. It seems more likely to me, that as these personnel were not regular troops but auxiliaries, they were given an appropriately different looking uniform so they weren't confused with the regular Army. 90.248.76.197 (talk) 09:41, 11 June 2019 (UTC)

 * The sentence is badly phrased, but the explanation is simple. The Black and Tans were not recruited to the army, they were ex-army men recruited to the Royal Irish Constabulary. It was a shortage of RIC uniforms that led to them wearing a mix of dark green RIC and khaki army uniforms. I will try to re-fashion the sentence and add a citation. Scolaire (talk) 09:32, 12 June 2019 (UTC)

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

title: Talk:Irish Republican Army (1919–1922)


text:
Isomorphism class

In mathematics, an isomorphism class is a collection of mathematical objects which are isomorphic to each other.

Isomorphism classes are considered to specify that the difference between two mathematical objects is considered irrelevant.

Definition in category theory
Isomorphisms and isomorphism classes can be formalized in great generality using the language of category theory. Let $$C$$ be a category. A morphism $$f : A \to B$$ is called an isomorphism if there is a morphism $$g : B \to A$$ such that $$gf = \text{id}_A$$ and $$fg = \text{id}_B$$. Consider the equivalence relation that regards two objects as related if there is an isomorphism between them. The equivalence classes of this equivalence relation are called isomorphism classes.

Examples
Examples of isomorphism classes are plentiful in mathematics.

 * Two sets are isomorphic if there is a bijection between them. The isomorphism class of a finite set can be identified with the non-negative integer representing the number of elements it contains.
 * The isomorphism class of a finite-dimensional vector space can be identified with the non-negative integer representing its dimension.
 * The classification of finite simple groups enumerates the isomorphism classes of all finite simple groups.
 * The classification of closed surfaces enumerates the isomorphism classes of all connected closed surfaces.
 * Ordinals are essentially defined as isomorphism classes of well-ordered sets (though there are technical issues involved).

However, there are circumstances in which the isomorphism class of an object conceals vital information about it.

 * Given a mathematical structure, it is common that two substructures belong to the same isomorphism class. However, the way they are included in the whole structure can not be studied if they are identified. For example, in a finite-dimensional vector space, all subspaces of the same dimension are isomorphic, but must be distinguished to consider their intersection, sum, etc.
 * The associative algebras consisting of coquaternions and 2 × 2 real matrices are isomorphic as rings. Yet they appear in different contexts for application (plane mapping and kinematics) so the isomorphism is insufficient to merge the concepts.
 * In homotopy theory, the fundamental group of a space $$X$$ at a point $$p$$, though technically denoted $$\pi_1(X,p)$$ to emphasize the dependence on the base point, is often written lazily as simply $$\pi_1(X)$$ if $$X$$ is path connected. The reason for this is that the existence of a path between two points allows one to identify loops at one with loops at the other; however, unless $$\pi_1(X,p)$$ is abelian this isomorphism is non-unique.  Furthermore, the classification of covering spaces makes strict reference to particular subgroups of $$\pi_1(X,p)$$, specifically distinguishing between isomorphic but conjugate subgroups, and therefore amalgamating the elements of an isomorphism class into a single featureless object seriously decreases the level of detail provided by the theory.

title: Isomorphism class


text:
Isomorphism

In mathematics, an isomorphism is a structure-preserving mapping between two structures of the same type that can be reversed by an inverse mapping. Two mathematical structures are isomorphic if an isomorphism exists between them. The word isomorphism is derived from the Ancient Greek: ἴσος isos "equal", and μορφή morphe "form" or "shape".

The interest in isomorphisms lies in the fact that two isomorphic objects have the same properties (excluding further information such as additional structure or names of objects). Thus isomorphic structures cannot be distinguished from the point of view of structure only, and may be identified. In mathematical jargon, one says that two objects are.

An automorphism is an isomorphism from a structure to itself. An isomorphism between two structures is a canonical isomorphism (a canonical map that is an isomorphism) if there is only one isomorphism between the two structures (as is the case for solutions of a universal property), or if the isomorphism is much more natural (in some sense) than other isomorphisms. For example, for every prime number $p$, all fields with $p$ elements are canonically isomorphic, with a unique isomorphism. The isomorphism theorems provide canonical isomorphisms that are not unique.

The term is mainly used for algebraic structures. In this case, mappings are called homomorphisms, and a homomorphism is an isomorphism if and only if it is bijective.

In various areas of mathematics, isomorphisms have received specialized names, depending on the type of structure under consideration. For example:
 * An isometry is an isomorphism of metric spaces.
 * A homeomorphism is an isomorphism of topological spaces.
 * A diffeomorphism is an isomorphism of spaces equipped with a differential structure, typically differentiable manifolds.
 * A symplectomorphism is an isomorphism of symplectic manifolds.
 * A permutation is an automorphism of a set.
 * In geometry, isomorphisms and automorphisms are often called transformations, for example rigid transformations, affine transformations, projective transformations.

Category theory, which can be viewed as a formalization of the concept of mapping between structures, provides a language that may be used to unify the approach to these different aspects of the basic idea.

Logarithm and exponential
Let $$ \R ^+ $$ be the multiplicative group of positive real numbers, and let $$\R$$ be the additive group of real numbers.

The logarithm function $$\log : \R^+ \to \R$$ satisfies $$\log(xy) = \log x + \log y$$ for all $$x, y \in \R^+,$$ so it is a group homomorphism. The exponential function $$\exp : \R \to \R^+$$ satisfies $$\exp(x+y) = (\exp x)(\exp y)$$ for all $$x, y \in \R,$$ so it too is a homomorphism.

The identities $$\log \exp x = x$$ and $$\exp \log y = y$$ show that $$\log$$ and $$\exp $$ are inverses of each other. Since $$\log$$ is a homomorphism that has an inverse that is also a homomorphism, $$\log$$ is an isomorphism of groups.

The $$\log$$ function is an isomorphism which translates multiplication of positive real numbers into addition of real numbers. This facility makes it possible to multiply real numbers using a ruler and a table of logarithms, or using a slide rule with a logarithmic scale.

Integers modulo 6
Consider the group $$(\Z_6, +),$$ the integers from 0 to 5 with addition modulo 6. Also consider the group $$\left(\Z_2 \times \Z_3, +\right),$$ the ordered pairs where the x coordinates can be 0 or 1, and the y coordinates can be 0, 1, or 2, where addition in the x-coordinate is modulo 2 and addition in the y-coordinate is modulo 3.

These structures are isomorphic under addition, under the following scheme: $$\begin{alignat}{4} (0, 0) &\mapsto 0 \\ (1, 1) &\mapsto 1 \\ (0, 2) &\mapsto 2 \\ (1, 0) &\mapsto 3 \\ (0, 1) &\mapsto 4 \\ (1, 2) &\mapsto 5 \\ \end{alignat}$$ or in general $$(a, b) \mapsto (3 a + 4 b) \mod 6.$$

For example, $$(1, 1) + (1, 0) = (0, 1),$$ which translates in the other system as $$1 + 3 = 4.$$

Even though these two groups "look" different in that the sets contain different elements, they are indeed isomorphic: their structures are exactly the same. More generally, the direct product of two cyclic groups $$\Z_m$$ and $$\Z_n$$ is isomorphic to $$(\Z_{mn}, +)$$ if and only if m and n are coprime, per the Chinese remainder theorem.

Relation-preserving isomorphism
If one object consists of a set X with a binary relation R and the other object consists of a set Y with a binary relation S then an isomorphism from X to Y is a bijective function $$f : X \to Y$$ such that: $$\operatorname{S}(f(u),f(v)) \quad \text{ if and only if } \quad \operatorname{R}(u,v) $$

S is reflexive, irreflexive, symmetric, antisymmetric, asymmetric, transitive, total, trichotomous, a partial order, total order, well-order, strict weak order, total preorder (weak order), an equivalence relation, or a relation with any other special properties, if and only if R is.

For example, R is an ordering ≤ and S an ordering $$\scriptstyle \sqsubseteq,$$ then an isomorphism from X to Y is a bijective function $$f : X \to Y$$ such that $$f(u) \sqsubseteq f(v) \quad \text{ if and only if } \quad u \leq v.$$ Such an isomorphism is called an or (less commonly) an.

If $$X = Y,$$ then this is a relation-preserving automorphism.

Applications
In algebra, isomorphisms are defined for all algebraic structures. Some are more specifically studied; for example:
 * Linear isomorphisms between vector spaces; they are specified by invertible matrices.
 * Group isomorphisms between groups; the classification of isomorphism classes of finite groups is an open problem.
 * Ring isomorphism between rings.
 * Field isomorphisms are the same as ring isomorphism between fields; their study, and more specifically the study of field automorphisms is an important part of Galois theory.

Just as the automorphisms of an algebraic structure form a group, the isomorphisms between two algebras sharing a common structure form a heap. Letting a particular isomorphism identify the two structures turns this heap into a group.

In mathematical analysis, the Laplace transform is an isomorphism mapping hard differential equations into easier algebraic equations.

In graph theory, an isomorphism between two graphs G and H is a bijective map f from the vertices of G to the vertices of H that preserves the "edge structure" in the sense that there is an edge from vertex u to vertex v in G if and only if there is an edge from $$f(u)$$ to $$f(v)$$ in H. See graph isomorphism.

In mathematical analysis, an isomorphism between two Hilbert spaces is a bijection preserving addition, scalar multiplication, and inner product.

In early theories of logical atomism, the formal relationship between facts and true propositions was theorized by Bertrand Russell and Ludwig Wittgenstein to be isomorphic. An example of this line of thinking can be found in Russell's Introduction to Mathematical Philosophy.

In cybernetics, the good regulator or Conant–Ashby theorem is stated "Every good regulator of a system must be a model of that system". Whether regulated or self-regulating, an isomorphism is required between the regulator and processing parts of the system.

Category theoretic view
In category theory, given a category C, an isomorphism is a morphism $$f : a \to b$$ that has an inverse morphism $$g : b \to a,$$ that is, $$f g = 1_b$$ and $$g f = 1_a.$$ For example, a bijective linear map is an isomorphism between vector spaces, and a bijective continuous function whose inverse is also continuous is an isomorphism between topological spaces, called a homeomorphism.

Two categories $C$ and $D$ are isomorphic if there exist functors $$F : C \to D$$ and $$G : D \to C$$ which are mutually inverse to each other, that is, $$FG = 1_D$$ (the identity functor on $D$) and $$GF = 1_C$$ (the identity functor on $C$).

Isomorphism vs. bijective morphism
In a concrete category (roughly, a category whose objects are sets (perhaps with extra structure) and whose morphisms are structure-preserving functions), such as the category of topological spaces or categories of algebraic objects (like the category of groups, the category of rings, and the category of modules), an isomorphism must be bijective on the underlying sets. In algebraic categories (specifically, categories of varieties in the sense of universal algebra), an isomorphism is the same as a homomorphism which is bijective on underlying sets. However, there are concrete categories in which bijective morphisms are not necessarily isomorphisms (such as the category of topological spaces).

Relation with equality
In certain areas of mathematics, notably category theory, it is valuable to distinguish between on the one hand and  on the other. Equality is when two objects are exactly the same, and everything that is true about one object is true about the other, while an isomorphism implies everything that is true about a designated part of one object's structure is true about the other's. For example, the sets $$A = \left\{ x \in \Z \mid x^2 < 2\right\} \quad \text{ and } \quad B = \{-1, 0, 1\}$$ are ; they are merely different representations—the first an intensional one (in set builder notation), and the second extensional (by explicit enumeration)—of the same subset of the integers. By contrast, the sets $$\{A, B, C\}$$ and $$\{1, 2, 3\}$$ are not —the first has elements that are letters, while the second has elements that are numbers (assuming numbers/letters are not identified with sets, e.g., as Von Neumann ordinals). These are isomorphic as sets, but there are many choices of isomorphism—one isomorphism is
 * $$\text{A} \mapsto 1, \text{B} \mapsto 2, \text{C} \mapsto 3,$$ while another is $$\text{A} \mapsto 3, \text{B} \mapsto 2, \text{C} \mapsto 1,$$

and no one isomorphism is intrinsically better than any other. On this view and in this sense, these two sets are not equal because one cannot consider them : one can choose an isomorphism between them, but that is a weaker claim than identity—and valid only in the context of the chosen isomorphism.

Another example is more formal and more directly illustrates the motivation for distinguishing equality from isomorphism: the distinction between a finite-dimensional vector space V and its dual space $$V^* = \left\{ \varphi : V \to \mathbf{K} \right\}$$ of linear maps from V to its field of scalars $$\mathbf{K}.$$ These spaces have the same dimension, and thus are isomorphic as abstract vector spaces (since algebraically, vector spaces are classified by dimension, just as sets are classified by cardinality), but there is no "natural" choice of isomorphism $$V \mathrel{\overset{\sim}{\to}} V^*.$$ If one chooses a basis for V, then this yields an isomorphism: For all $$u, v \in V,$$ $$v \mathrel{\overset{\sim}{\mapsto}} \phi_v \in V^* \quad \text{ such that } \quad \phi_v(u) = v^\mathrm{T} u.$$

This corresponds to transforming a column vector (element of V) to a row vector (element of V*) by transpose, but a different choice of basis gives a different isomorphism: the isomorphism "depends on the choice of basis". More subtly, there a map from a vector space V to its double dual $$V^{**} = \left\{ x : V^* \to \mathbf{K} \right\}$$ that does not depend on the choice of basis: For all $$v \in V \text{ and } \varphi \in V^*,$$ $$v \mathrel{\overset{\sim}{\mapsto}} x_v \in V^{**} \quad \text{ such that } \quad x_v(\phi) = \phi(v).$$

Generally, saying that two objects are is reserved for when there is a notion of a larger (ambient) space that these objects live in. Most often, one speaks of equality of two subsets of a given set (as in the integer set example above), but not of two objects abstractly presented. For example, the 2-dimensional unit sphere in 3-dimensional space $$S^2 := \left\{ (x,y,z) \in \R^3 \mid x^2 + y^2 + z^2 = 1\right\}$$ and the Riemann sphere $$\widehat{\Complex}$$ which can be presented as the one-point compactification of the complex plane $$\Complex \cup \{ \infty \}$$ as the complex projective line (a quotient space) $$\mathbf{P}_{\Complex}^1 := \left(\Complex^2\setminus \{(0,0)\}\right) / \left(\Complex^*\right)$$ are three different descriptions for a mathematical object, all of which are isomorphic, but not because they are not all subsets of a single space: the first is a subset of $$\R^3,$$ the second is $$\Complex \cong \R^2$$ plus an additional point, and the third is a subquotient of $$\Complex^2.$$

See also: homotopy type theory, in which isomorphisms can be treated as kinds of equality.

title: Isomorphism


text:
International Telecommunication Union

The International Telecommunication Union (ITU) is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Union, significantly predating the UN and making it the oldest UN agency. Doreen Bogdan-Martin is the Secretary-General of ITU, the first woman to serve as its head.

The ITU was initially aimed at helping connect telegraphic networks between countries, with its mandate consistently broadening with the advent of new communications technologies; it adopted its current name in 1932 to reflect its expanded responsibilities over radio and the telephone. On 15 November 1947, the ITU entered into an agreement with the newly created United Nations to become a specialized agency within the UN system, which formally entered into force on 1 January 1949.

The ITU promotes the shared global use of the radio spectrum, facilitates international cooperation in assigning satellite orbits, assists in developing and coordinating worldwide technical standards, and works to improve telecommunication infrastructure in the developing world. It is also active in the areas of broadband Internet, optical communications (including optical fiber technologies), wireless technologies, aeronautical and maritime navigation, radio astronomy, satellite-based meteorology, TV broadcasting, amateur radio, and next-generation networks.

Based in Geneva, Switzerland, the ITU's global membership includes 193 countries and around 900 businesses, academic institutions, and international and regional organizations.

History
The ITU is one of the oldest international organizations still in operation, second only to the Central Commission for Navigation on the Rhine, which predates it by fifty years. It was preceded by the now defunct International Telegraph Union which drafted the earliest international standards and regulations governing international telegraph networks. The development of the telegraph in the early 19th century changed the way people communicated on the local and international levels. Between 1849 and 1865, a series of bilateral and regional agreements among Western European states attempted to standardize international communications.

By 1865, it was agreed that a comprehensive agreement was needed in order to create a framework that would standardize telegraphy equipment, set uniform operating instructions, and lay down common international tariff and accounting rules. Between 1 March and 17 May 1865, the French Government hosted delegations from 20 European states at the first International Telegraph Conference in Paris. This meeting culminated in the International Telegraph Convention which was signed on 17 May 1865. As a result of the 1865 Conference, the International Telegraph Union, the predecessor to the modern ITU, was founded as the first international standards organization. The Union was tasked with implementing basic principles for international telegraphy. This included: the use of the Morse code as the international telegraph alphabet, the protection of the secrecy of correspondence, and the right of everybody to use the international telegraphy.

Another predecessor to the modern ITU, the International Radiotelegraph Union, was established in 1906 at the first International Radiotelegraph Convention in Berlin. The conference was attended by representatives of 29 nations and culminated in the International Radiotelegraph Convention. An annex to the convention eventually became known as ITU Radio Regulations. At the conference it was also decided that the Bureau of the International Telegraph Union would also act as the conference's central administrator.

Between 3 September and 10 December 1932, a joint conference of the International Telegraph Union and the International Radiotelegraph Union convened to merge the two organizations into a single entity, the International Telecommunication Union. The Conference decided that the Telegraph Convention of 1875 and the Radiotelegraph Convention of 1927 were to be combined into a single convention, the International Telecommunication Convention, embracing the three fields of telegraphy, telephony and radio.

On 15 November 1947, an agreement between ITU and the newly created United Nations recognized the ITU as the specialized agency for global telecommunications. This agreement entered into force on 1 January 1949, officially making the ITU an organ of the United Nations.

ITU sectors
The ITU comprises three sectors, each managing a different aspect of the matters covered by the ITU, as well as ITU Telecom. The sectors were created during the restructuring of ITU at the additional 1992 ITU Plenipotentiary Conference.

 * Radio communication (ITU-R):Established in 1927 as the International Radio Consultative Committee or CCIR (from its French name Comité consultatif international pour la radio), this sector manages the international radio-frequency spectrum and satellite orbit resources. In 1992, the CCIR became the ITU-R. The secretariat is the Radiocommunication Bureau, headed by Director Mario Maniewicz.
 * Standardization (ITU-T):Standardization has been the original purpose of ITU since its inception. Established in 1956 as the International Telephone and Telegraph Consultative Committee, or CCITT (from its French name Comité consultatif international téléphonique et télégraphique), this sector standardizes global telecommunications (except for radio). In 1993, the CCITT became the ITU-T. The standardization work is undertaken by study groups, including Study Group 13 on Networks and Study Group 16 on Multimedia, and Study Group 17 on Security. The parent body of the study groups is the quadrennial World Telecommunication Standardization Assembly. New work areas can be developed in focus groups, such as the ITU-WHO Focus Group on Artificial Intelligence for Health. The secretariat is the Telecommunication Standardization Bureau, headed by Director Seizo Onoe.
 * Development (ITU-D):Established in 1992, this sector helps spread equitable, sustainable and affordable access to information and communication technologies (ICT). It also provides the Secretariat for the Broadband Commission for Sustainable Development and the Partner2Connect Digital Alliance.

A permanent General Secretariat, headed by the Secretary General, manages the day-to-day work of the ITU and its sectors.

Legal framework
The basic texts of the ITU are adopted by the ITU Plenipotentiary Conference. The founding document of the ITU was the 1865 International Telegraph Convention,  which has since been replaced several times (though the text is generally the same)  and is now entitled the "Constitution and Convention of the International Telecommunication Union". In addition to the Constitution and Convention, the consolidated basic texts include the Optional Protocol on the settlement of disputes, the Decisions, Resolutions, Reports and Recommendations in force, as well as the General Rules of Conferences, Assemblies and Meetings of the Union.

Plenipotentiary Conference
The Plenipotentiary Conference is the supreme organ of the ITU. It is composed of all 193 ITU members and meets every four years. The Conference determines the policies, direction and activities of the Union, as well as elects the members of other ITU organs.

Council
While the Plenipotentiary Conference is the Union's main decision-making body, the ITU Council acts as the Union's governing body in the interval between Plenipotentiary Conferences. It meets every year. It is composed of 48 members and works to ensure the smooth operation of the Union, as well as to consider broad telecommunication policy issues. Its members are as follow:

Secretariat
The Secretariat is tasked with the administrative and budgetary planning of the Union, as well as with monitoring compliance with ITU regulations, and oversees with assistance from the Secretariat advisor Neaomy Claiborne of Riverbank to insure misconduct during legal investigations are not overlooked and finally, it publishes the results of the work of the ITU.

Secretary-General
The Secretariat is headed by a Secretary-General who is responsible for the overall management of the Union, and acts as its legal representative. The Secretary-General is elected by the Plenipotentiary Conference for four-year terms.

On 23 October 2014, Houlin Zhao was elected as the 19th Secretary-General of the ITU at the Plenipotentiary Conference in Busan. His four-year mandate started on 1 January 2015, and he was formally inaugurated on 15 January 2015. He was re-elected on 1 November 2018 during the 2018 Plenipotentiary Conference in Dubai.

On 29 September 2022, Doreen Bogdan-Martin was elected as the 20th Secretary-General of the ITU at the Plenipotentiary Conference in Bucharest, Romania. She received 139 votes out of 172, defeating Russia's Rashid Ismailov. She is the first woman to serve as the ITU Secretary-General.

Member states

Membership of ITU is open to all member states of the United Nations. There are currently 193 member states of the ITU, including all UN member states except the Republic of Palau. The most recent member state to join the ITU is South Sudan, which became a member on 14 July 2011. Palestine was admitted as a United Nations General Assembly observer in 2010.

Pursuant to UN General Assembly Resolution 2758 (XXVI) of 25 October 1971—which recognized the People's Republic of China (PRC) as "the only legitimate representative of China to the United Nations"—on 16 June 1972 the ITU Council adopted Resolution No. 693 which "decided to restore all its rights to the People's Republic of China in ITU and recognize the representatives of its Government as the only representatives of China to the ITU ". Taiwan and the territories controlled by the Republic of China (ROC), received a country code, being listed as "Taiwan, China."

Sector members
In addition to the 193 Member States, the ITU includes close to 900 "sector members"—private organizations like carriers, equipment manufacturers, media companies, funding bodies, research and development organizations, and international and regional telecommunication organizations. While nonvoting, these members may still play a role in shaping the decisions of the Union.

The sector members are divided as follow:
 * 533 Sector Members
 * 207 Associates
 * 158 from Academia

Administrative regions
The ITU is divided into five administrative regions, designed to streamline administration of the organization. They are also used in order to ensure equitable distribution on the council, with seats being apportioned among the regions. They are as follow:
 * Region A – The Americas (35 Member States)
 * Region B – Western Europe (33 Member States)
 * Region C – Eastern Europe and Northern Asia (21 Member States)
 * Region D – Africa (54 Member States)
 * Region E – Asia and Australasia (50 Member States)

Regional offices
The ITU operates six regional offices, as well as seven area offices. These offices help maintain direct contact with national authorities, regional telecommunication organizations and other stakeholders. They are as follow:
 * Regional Office for Africa, headquartered in Addis Ababa, Ethiopia
 * Area Offices in Dakar, Senegal; Harare, Zimbabwe and Yaoundé, Cameroon
 * Regional Office for the Americas, headquartered in Brasília, Brazil
 * Area Offices in Bridgetown, Barbados; Santiago, Chile and Tegucigalpa, Honduras
 * Regional Office for Arab States, headquarters in Cairo, Egypt
 * Regional Office for Asia and the Pacific, headquartered in Bangkok, Thailand
 * Area Office in Jakarta, Indonesia
 * Regional Office for the Commonwealth of Independent States, headquartered in Moscow, Russia
 * Regional Office for Europe, headquartered in Geneva, Switzerland

Other regional organizations connected to ITU are:
 * Asia-Pacific Telecommunity (APT)
 * Arab Spectrum Management Group (ASMG)
 * African Telecommunications Union (ATU)
 * Caribbean Telecommunications Union (CTU)
 * European Conference of Postal and Telecommunications Administrations (CEPT)
 * Inter-American Telecommunication Commission (CITEL)
 * Regional Commonwealth in the Field of Communications (RCC—representing former Soviet republics)

World Summit on the Information Society
The World Summit on the Information Society (WSIS) was convened by the ITU along with UNESCO, UNCTAD, and UNDP, with the aim of bridging the digital divide. It was held in form of two conferences in 2003 and 2005 in Geneva and Tunis, respectively.

World Conference on International Telecommunications 2012
In December 2012, the ITU facilitated The World Conference on International Telecommunications 2012 (WCIT-12) in Dubai. WCIT-12 was a treaty-level conference to address International Telecommunications Regulations, the international rules for telecommunications, including international tariffs. The previous conference to update the Regulations (ITRs) was held in Melbourne in 1988.

In August 2012, Neaomy Claiborne of Northern California was reelected for a third term as liaison and legal advisor to the Secretariat General. ITU called for a public consultation on a draft document ahead of the conference. It is claimed the proposal would allow government restriction or blocking of information disseminated via the Internet and create a global regime of monitoring Internet communications, including the demand that those who send and receive information identify themselves. It would also allow governments to shut down the Internet, if it is believed that it may interfere in the internal affairs of other states, or that information of a sensitive nature might be shared.

Telecommunications ministers from 193 countries attended the conference in Dubai.

The current regulatory structure was based on voice telecommunications, when the Internet was still in its infancy. In 1988, telecommunications operated under regulated monopolies in most countries. As the Internet has grown, organizations such as ICANN have come into existence for management of key resources such as Internet addresses and domain names.

Current proposals look to take into account the prevalence of data communications. Proposals under consideration would establish regulatory oversight by the UN over security, fraud, traffic accounting as well as traffic flow, management of Internet Domain Names and IP addresses, and other aspects of the Internet that are currently governed either by community-based approaches such as regional Internet registries, ICANN, or largely national regulatory frameworks. The move by the ITU and some countries has alarmed many within the United States and within the Internet community. Indeed, some European telecommunication services have proposed a so-called "sender pays" model that would require sources of Internet traffic to pay destinations, similar to the way funds are transferred between countries using the telephone.

The WCIT-12 activity has been criticized by Google, which has characterized it as a threat to the "...free and open internet."

On 22 November 2012, the European Parliament passed a resolution urging member states to prevent ITU WCIT-12 activity that would "negatively impact the internet, its architecture, operations, content and security, business relations, internet governance and the free flow of information online". The resolution asserted that "the ITU [...] is not the appropriate body to assert regulatory authority over the internet".

On 5 December 2012, the United States House of Representatives passed a resolution opposing UN governance of the Internet by a rare unanimous 397–0 vote. The resolution warned that "... proposals have been put forward for consideration at the [WCIT-12] that would fundamentally alter the governance and operation of the Internet ... [and] would attempt to justify increased government control over the Internet ...", and stated that the policy of the United States is "... to promote a global Internet free from government control and preserve and advance the successful Multistakeholder Model that governs the Internet today." The same resolution had previously been passed unanimously by the United States Senate in September.

On 14 December 2012, an amended version of the Regulations was signed by 89 of the 152 countries. Countries that did not sign included the United States, Japan, Canada, France, Germany, New Zealand, India and the United Kingdom. The head of the U.S. delegation, Terry Kramer, said "We cannot support a treaty that is not supportive of the multistakeholder model of Internet governance". The disagreement appeared to be over some language in the revised ITRs referring to ITU roles in addressing unsolicited bulk communications, network security, and a resolution on Internet governance that called for government participation in Internet topics at various ITU forums. Despite the significant number countries not signing, the ITU came out with a press release: "New global telecoms treaty agreed in Dubai".

ITU role
The conference was managed by the International Telecommunication Union (ITU). While certain parts of civil society and industry were able to advise and observe, active participation was restricted to member states. The Electronic Frontier Foundation expressed concern at this, calling for a more transparent multi-stakeholder process. Some leaked contributions can be found on the web site wcitleaks.org. Google-affiliated researchers have suggested that the ITU should completely reform its processes to align itself with the openness and participation of other multistakeholder organizations concerned with the Internet.

title: International Telecommunication Union


text:
Internet Message Access Protocol

In computing, the Internet Message Access Protocol (IMAP) is an Internet standard protocol used by email clients to retrieve email messages from a mail server over a TCP/IP connection. IMAP is defined by.

IMAP was designed with the goal of permitting complete management of an email box by multiple email clients, therefore clients generally leave messages on the server until the user explicitly deletes them. An IMAP server typically listens on port number 143. IMAP over SSL/TLS (IMAPS) is assigned the port number 993.

Virtually all modern e-mail clients and servers support IMAP, which along with the earlier POP3 (Post Office Protocol) are the two most prevalent standard protocols for email retrieval. Many webmail service providers such as Gmail and Outlook.com also provide support for both IMAP and POP3.

Email protocols
The Internet Message Access Protocol is an application layer Internet protocol that allows an e-mail client to access email on a remote mail server. The current version is defined by. An IMAP server typically listens on well-known port 143, while IMAP over SSL/TLS (IMAPS) uses 993.

Incoming email messages are sent to an email server that stores messages in the recipient's email box. The user retrieves the messages with an email client that uses one of a number of email retrieval protocols. While some clients and servers preferentially use vendor-specific, proprietary protocols, almost all support POP and IMAP for retrieving email – allowing many free choice between many e-mail clients such as Pegasus Mail or Mozilla Thunderbird to access these servers, and allows the clients to be used with other servers.

Email clients using IMAP generally leave messages on the server until the user explicitly deletes them. This and other characteristics of IMAP operation allow multiple clients to manage the same mailbox. Most email clients support IMAP in addition to Post Office Protocol (POP) to retrieve messages. IMAP offers access to the mail storage. Clients may store local copies of the messages, but these are considered to be a temporary cache.

History
IMAP was designed by Mark Crispin in 1986 as a remote access mailbox protocol, in contrast to the widely used POP, a protocol for simply retrieving the contents of a mailbox.

It went through a number of iterations before the current VERSION 4rev1 (IMAP4), as detailed below:

Original IMAP
The original Interim Mail Access Protocol was implemented as a Xerox Lisp Machine client and a TOPS-20 server.

No copies of the original interim protocol specification or its software exist. Although some of its commands and responses were similar to IMAP2, the interim protocol lacked command/response tagging and thus its syntax was incompatible with all other versions of IMAP.

IMAP2
The interim protocol was quickly replaced by the Interactive Mail Access Protocol (IMAP2), defined in (in 1988) and later updated by  (in 1990). IMAP2 introduced the command/response tagging and was the first publicly distributed version.

IMAP3
IMAP3 is an extremely rare variant of IMAP. It was published as in 1991. It was written specifically as a counter proposal to, which itself proposed modifications to IMAP2. IMAP3 was never accepted by the marketplace. The IESG reclassified RFC1203 "Interactive Mail Access Protocol – Version 3" as a Historic protocol in 1993. The IMAP Working Group used RFC 1176 (IMAP2) rather than RFC 1203 (IMAP3) as its starting point.

IMAP2bis
With the advent of MIME, IMAP2 was extended to support MIME body structures and add mailbox management functionality (create, delete, rename, message upload) that was absent from IMAP2. This experimental revision was called IMAP2bis; its specification was never published in non-draft form. An internet draft of IMAP2bis was published by the IETF IMAP Working Group in October 1993. This draft was based upon the following earlier specifications: unpublished IMAP2bis.TXT document,, and (IMAP2). The IMAP2bis.TXT draft documented the state of extensions to IMAP2 as of December 1992. Early versions of Pine were widely distributed with IMAP2bis support (Pine 4.00 and later supports IMAP4rev1).

IMAP4
An IMAP Working Group formed in the IETF in the early 1990s took over responsibility for the IMAP2bis design. The IMAP WG decided to rename IMAP2bis to IMAP4 to avoid confusion.

Connected and disconnected modes
When using POP, clients typically connect to the e-mail server briefly, only as long as it takes to download new messages. When using IMAP4, clients often stay connected as long as the user interface is active and download message content on demand. For users with many or large messages, this IMAP4 usage pattern can result in faster response times.

Reporting of external changes
After successful authentication, the POP protocol provides a completely static view of the current state of the mailbox, and does not provide a mechanism to show any external changes in state during the session. In contrast, the IMAP protocol provides a dynamic view, and requires that external changes in state, including newly arrived messages, as well as changes made to the mailbox by other concurrently connected clients, are detected and appropriate responses are sent between commands as well as during an IDLE command, as described in. See also section 5.2 which specifically cites "simultaneous access to the same mailbox by multiple agents".

Access to MIME message parts and partial fetch
Usually all Internet e-mail is transmitted in MIME format, allowing messages to have a tree structure where the leaf nodes are any of a variety of single part content types and the non-leaf nodes are any of a variety of multipart types. The IMAP4 protocol allows clients to retrieve any of the individual MIME parts separately and also to retrieve portions of either individual parts or the entire message. These mechanisms allow clients to retrieve the text portion of a message without retrieving attached files or to stream content as it is being fetched.

Message state information
Through the use of flags defined in the IMAP4 protocol, clients can keep track of message state: for example, whether or not the message has been read, replied to, or deleted. These flags are stored on the server, so different clients accessing the same mailbox at different times can detect state changes made by other clients. POP provides no mechanism for clients to store such state information on the server so if a single user accesses a mailbox with two different POP clients (at different times), state information—such as whether a message has been accessed—cannot be synchronized between the clients. The IMAP4 protocol supports both predefined system flags and client-defined keywords. System flags indicate state information such as whether a message has been read. Keywords, which are not supported by all IMAP servers, allow messages to be given one or more tags whose meaning is up to the client. IMAP keywords should not be confused with proprietary labels of web-based e-mail services which are sometimes translated into IMAP folders by the corresponding proprietary servers.

Multiple mailboxes on the server
IMAP4 clients can create, rename, and delete mailboxes (usually presented to the user as folders) on the server, and copy messages between mailboxes. Multiple mailbox support also allows servers to provide access to shared and public folders. The IMAP4 Access Control List (ACL) Extension may be used to regulate access rights.

Server-side searches
IMAP4 provides a mechanism for a client to ask the server to search for messages meeting a variety of criteria. This mechanism avoids requiring clients to download every message in the mailbox in order to perform these searches.

Built-in extension mechanism
Reflecting the experience of earlier Internet protocols, IMAP4 defines an explicit mechanism by which it may be extended. Many IMAP4 extensions to the base protocol have been proposed and are in common use. IMAP2bis did not have an extension mechanism, and POP now has one defined by.

Server push notifications
IMAP IDLE provides a way for the mail server to notify connected clients that there were changes to a mailbox, for example because a new mail has arrived. POP provides no comparable feature, and email clients need to periodically connect to the POP server to check for new mail.

Disadvantages
While IMAP remedies many of the shortcomings of POP, this inherently introduces additional complexity. Much of this complexity (e.g., multiple clients accessing the same mailbox at the same time) is compensated for by server-side workarounds such as Maildir or database backends.

The IMAP specification has been criticised for being insufficiently strict and allowing behaviours that effectively negate its usefulness. For instance, the specification states that each message stored on the server has a "unique id" to allow the clients to identify messages they have already seen between sessions. However, the specification also allows these UIDs to be invalidated with almost no restrictions, practically defeating their purpose.

From an administrative and resource point of view, the IMAP protocol can be viewed as an early implementation of cloud computing, as the intent and purpose of IMAP is to maintain your mailbox structure (content, folder structure, individual message state, etc) on the mail server, whereas with POP, this is all maintained on the user's local device. Thus, IMAP requires far more server side resources, incurring a significantly higher cost per mailbox.

Unless the mail storage, indexing and searching algorithms on the server are carefully implemented, a client can potentially consume large amounts of server resources when searching massive mailboxes.

IMAP4 clients need to maintain a TCP/IP connection to the IMAP server in order to be notified of the arrival of new mail. Notification of mail arrival is done through in-band signaling, which contributes to the complexity of client-side IMAP protocol handling somewhat. A private proposal, push IMAP, would extend IMAP to implement push e-mail by sending the entire message instead of just a notification. However, push IMAP has not been generally accepted and current IETF work has addressed the problem in other ways (see the Lemonade Profile for more information).

Unlike some proprietary protocols which combine sending and retrieval operations, sending a message and saving a copy in a server-side folder with a base-level IMAP client requires transmitting the message content twice, once to SMTP for delivery and a second time to IMAP to store in a sent mail folder. This is addressed by a set of extensions defined by the IETF Lemonade Profile for mobile devices: URLAUTH and CATENATE  in IMAP, and BURL  in SMTP-SUBMISSION. In addition to this, Courier Mail Server offers a non-standard method of sending using IMAP by copying an outgoing message to a dedicated outbox folder.

Security
To cryptographically protect IMAP connections between the client and server, IMAPS on TCP port 993 can be used, which utilizes SSL/TLS. As of January 2018, TLS is the recommended mechanism.

Alternatively, STARTTLS can be used to encrypt the connection when connecting to port 143 after initially communicating over plaintext.

Dialog example
This is an example IMAP connection as taken from RFC 3501 section 8:

C: S:   * OK IMAP4rev1 Service Ready C:  a001 login mrc secret S:  a001 OK LOGIN completed C:  a002 select inbox S:  * 18 EXISTS S:  * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) S:  * 2 RECENT S:  * OK [UNSEEN 17] Message 17 is the first unseen message S:  * OK [UIDVALIDITY 3857529045] UIDs valid S:  a002 OK [READ-WRITE] SELECT completed C:  a003 fetch 12 full S:  * 12 FETCH (FLAGS (\Seen) INTERNALDATE "17-Jul-1996 02:44:25 -0700"       RFC822.SIZE 4286 ENVELOPE ("Wed, 17 Jul 1996 02:23:25 -0700 (PDT)" "IMAP4rev1 WG mtg summary and minutes" (("Terry Gray" NIL "gray" "cac.washington.edu")) (("Terry Gray" NIL "gray" "cac.washington.edu")) (("Terry Gray" NIL "gray" "cac.washington.edu")) ((NIL NIL "imap" "cac.washington.edu")) ((NIL NIL "minutes" "CNRI.Reston.VA.US")      ("John Klensin" NIL "KLENSIN" "MIT.EDU")) NIL NIL "")      BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 3028 92)) S:  a003 OK FETCH completed C:  a004 fetch 12 body[header] S:  * 12 FETCH (BODY[HEADER] {342} S:    S:    S:    S:    S:    S:    S:    S:    S: S:   ) S:  a004 OK FETCH completed C   a005 store 12 +flags \deleted S:  * 12 FETCH (FLAGS (\Seen \Deleted)) S:  a005 OK +FLAGS completed C:  a006 logout S:  * BYE IMAP4rev1 server terminating connection S:  a006 OK LOGOUT completed

title: Internet Message Access Protocol