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Talk:Command–query separation

3rd example in "Drawbacks"
"A CQS pattern suitable for multithreaded environment" is written above a method that returns a value by assigning it to an out parameter. Simply replacing "return x;" with "*ret = x;" is not Command-Query-Separation. Either the line labelling it as CQS or the snippet itself should be changed. --SealedSun (talk) 11:40, 17 July 2009 (UTC)

older entries
I'm not all that comfortable with the discussion of race conditions. I don't see how CQS reduces race conditions; if anything, it adds new ones. Avoiding race conditions wasn't one of the goals of CQS, and I don't see how it achieves that. At the very least, I think an example is warranted. --Doradus 00:23, 12 Aug 2003 (UTC)

 * No response in over a week, so I have removed the paragraph in question. For the record, here it is:

 * For example, eliminating value returns from state modifications avoids the possiblity of race conditions between old and new states. This may at first seem to over-complicate the program by requiring two methods to be used (with explicit synchronization in threaded systems) where before a single method would suffice, but in practice this actually makes explicit hidden assumptions about data dependencies which would otherwise be invisible to the programmer.

 * Anyone who wants to re-insert it ought at least to provide an example, but ideally should describe this in more detail. --Doradus 14:15, 21 Aug 2003 (UTC)

I just took a look at the current race condition coverage and I am not convinced that it is accurate. The current coverage states that breaking CQS by having one method change state and return a value will prevent a race condition. I don't believe that is the case, at least not with most programming languages. In the way most languages are interpreted or compiled and run in a multi-threaded environment, the thread scheduler can interrupt one thread at any point, even if the interrupt happens in the middle of a function call. My example is that your non-CQS function could get interrupted after it changed the state but before it returned the value. (In Java, the synchronized function modifier may ameliorate this partially, but that is a feature of one language, and even it is not fully safe.) Thus, your non-CQS function is just as susceptible to a race condition as a CQS function. Therefore, I believe that the original paragraph was correct in saying that CQS was superior by forcing you to handle all assumptions about data dependencies and synchronization explicitly. 66.92.232.102 17:07, 27 August 2007 (UTC)

Here's my thinking. Local variables are generally not susceptible to race conditions, because other threads can't access your stack frame. That makes them a handy way to avoid a race conditions:

set_field( new_value ): old_value = this.field; while compare_and_swap( this.field, old_value, new_value ) == false; return old_value;

The caller of this function is guaranteed that the returned value is what was in the field immediately before new_value was put there. I can think of no way to write this function in a CQS-compliant manner without locks. Can you? --Doradus 22:48, 27 August 2007 (UTC)

The example feels contrived. Nevertheless, I take your point is that the compare-and-swap atomic operation is a non-CQS routine, but it is a well-known hardware and operating system routine. I suppose that the answer is that all engineering is a trade-off. For the sake of code correctness and maintenance, you should strive to make all assumptions in your code explicit, rather than hiding them behind layer after layer of semantics. In general, if there is a data dependency between two or more values, this should be expressed with a lock. However, in some relatively rare circumstances the need for better performance justifies sacrificing some maintainability of the code. Hint: if you are not writing an operating system microkernel, enterprise-grade database engine, video game graphics engine, a massive scientific simulation, or a very resource-constained embedded program, you probably do not need to be doing this.

Furthermore, it is important to note that the atomicity of the non-CQS compare-and-swap function is only guaranteed by a hardware instruction. If we make exceptions for the handful of operating system routines that are atomic and non-CQS, we find that writing your own non-CQS functions does not guarantee atomicity. Using your example, your functional requirement is to read an old value from a shared variable, and replace it with a new value, and you have a data dependency between the old value and the new current value of the shared variable. To meet these functional requirements, two post conditions must hold true at the end of your function for all possible interleaving of threads: 1) the return value is the last value of the shared variable before the update occurred, and; 2) the value of the shared variable equals the value of new_value. Without a lock over the function call, your function still has a race condition! True, the compare_and_swap operation is atomic and the surrounding loop is guaranteed to replace the most recent old_value with new_value. (Except for a pathological race condition in which the thread is interrupted every time at the beginning or end of the loop and the shared variable is always changed, causing an infinite loop; such an interleaving feels contrived so I am giving you the benefit of the doubt.) However, what if the thread is interrupted immediately after the compare-and-swap has returned true but before the function returns? In that case, the value of the shared variable will not be new_value, but something unexpected.

Solutions: 1) Use CQS and explicit locks. Your data dependencies are explicit for all developers to see, or; 2) decide that performance trumps maintainability and use compare-and-swap directly, without wrapping it in a function. Note: It seems likely that if you truly have a data dependency between old_value and the new current value of the shared variable, you are going to end up performing several more operations on them, which usually entails locks. In conclusion, I still feel that the assertion that CQS reduces race conditions by forcing programmers to think explicitly about data dependencies and locks is warranted, with a few performance-related exceptions. 66.92.232.102 10:47, 28 August 2007 (UTC)

"devised by"
While it may be true that "it was devised by Bertrand Meyer as part of his pioneering work on the Eiffel programming language" (citation would be nice), that makes it sound like a great whole new idea. I doubt that it was so "pioneering" as that suggests. Even Pascal had the notion and separation of procedure (command) and function (query), though it likely didn't spell out that functions shall not touch the inner state (or maybe it did, don't have formal docs), and the third paragraph of the texts outlines nicely that it's quite analogical to the goto/control flow issue.

multi-threading issue
The examples fail to address what the issue is. It would be helpful if it stated explicitly what the pattern tries and why it fails.

AFAICS the pattern is (trying to be) a unique-key generator, i.e. subsequent calls of the function "value" shall return unique values. The first attempt "increase_x_and_return_it" is no more or less wrong in a multithreaded case than the last one (which is identical apart from syntax).

More specific, there are four operations:
 * 1. Get global key X.
 * 2. Increase local copy of X' to (X + 1)'.
 * 3. Store back (X + 1)' to X.
 * 4. Return (X + 1)'.

The article is more confusing than clarifying on the topic that steps 1-3 must be executed without interference, on the contrary it somehow gives the impression that step 4 matters - which doesn't.

The above comments in 'older entries' don't help much either:
 * 1. The compare_and_swap is IMHO rather pointless, because it actually just does the same thing the other examples do, but hidden behind a fancy name and working "correctly" (miraculously without explanation that it has to do the same amount of locking steps 1-3, programmers will know that it's *meant-to-be* an atomic operation on CPU level, but this is not an article for programmers who already know...)
 * 2. The compare_and_swap is even more wrong if you see it from the keygen angle: It again focuses on the notion that step 4 is the problem which it isn't. (Aside from that, it behaves unspecified if old_value is not equal to this.field (because another thread B executed the whole operation between thread A going from old_value := this.field to while compare_and_swap.)

"tracking the number of times queries have been issued essentially impossible"
A quote from the text:

It is noteworthy that rigid implementation of this specification makes tracking the number of times queries have been issued essentially impossible.

Can someone defend this claim? How does this principle make it impossible to track the number of queries? Please explain? — Preceding unsigned comment added by 89.31.193.191 (talk) 07:53, 4 July 2012 (UTC)

Tracking number of times queries have been issued needs a counting attribute in the object. On every querying the counter needs to be increased. Thus querying the object causes a state change of the object (change of an attribute of the object). — Preceding unsigned comment added by 91.115.216.188 (talk) 18:30, 11 August 2012 (UTC)

I deleted this comment since it has no source. At above: you seem to be discussing a specific language problem you're having. I suggest reading more about your language of choice. Comments appearing in a Wikipedia article should be cited. — Preceding unsigned comment added by 69.2.114.145 (talk) 15:46, 14 July 2014 (UTC)

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. 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: moved to Command–query separation. ErikHaugen (talk | contribs) 17:34, 31 January 2013 (UTC)

Command-query separation → ? –
 * Command-query are two things, not one thing so it should not use hyphen. The article deals with separation of commands from queries.

 * Command-query separation → Command/query separation ([ move]) – Use slash instead of hyphen? Frap (talk) 14:08, 23 January 2013 (UTC)

 * Support move to Command–query separation with an en dash. See WP:ENDASH at WP:MOS. A clear case. I think the proposal should be amended to that, instead of "?". N oetica Tea? 01:02, 24 January 2013 (UTC)
 * Oppose nominator's proposed location MOS:SLASH -- slashes cause problems. -- 76.65.128.43 (talk) 02:31, 24 January 2013 (UTC)
 * Support Command–query separation per Noetica. --BDD (talk) 18:57, 30 January 2013 (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.

Removed misleading section on multithreading
The current article has the following paragraph near the bottom:

Finally, here is a thread-safe CQS pattern. This preserves the separation between the mutation of state and reading the resulting value, without introducing a race condition in the caller:

However, if this is meant to be C++, calling  and   concurrently from two different threads definitely invokes undefined behavior (because the public   is read in   and modified in , with no synchronization). In Java, because "the memory model doesn't guarantee that you'll see the latest updates from one thread in another thread, without extra memory barriers of some kind", the behavior is also incorrect; "without any explicit volatility or locking, the other thread could see 0 forever." Basically, if  and   need to communicate between different processors, and you can look at the code for   and *see* that it doesn't contain any inter-processor communication primitives, then you *know* the code can't possibly work.

Therefore I'm removing the paragraph and code sample. –Quuxplusone (talk) 20:50, 28 February 2016 (UTC)

2nd example in "Drawbacks"
"In a multi-threaded program, there is a race condition in the caller, between where increment and value would be called:"

Shouldn't that be: "between the threads calling increment:"

A single read of a variable can not create a race condition, as in value.

And to follow CQS, shouldn't threads have their own copy of any object. If an object is to be modified, then it must be done in the parent thread.

Shawn H Corey (talk) 14:42, 26 February 2018 (UTC)

Error Handling
How does one do error-handling if commands are not allowed to return success/failure information? Antistone (talk) 20:18, 22 May 2018 (UTC)

Fluent interfaces in "See More"
Why does the "See More" section's sole link consist of the fluent interface page? There are no mentions of how it relates. If a method that evokes state change also returns a value, then this contradicts the summary's statement about commands not returning data. — Preceding unsigned comment added by Vvanpo (talk • contribs) 06:49, 18 October 2019 (UTC)

Other Architectural Patterns copied from Martin Fowler
The "Other Architectural Patterns" section is copied verbatim from https://martinfowler.com/bliki/CQRS.html — Preceding unsigned comment added by 67.208.190.2 (talk) 15:17, 29 September 2020 (UTC)

title: Talk:Command–query separation


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Honoré Jackson

William Henry Jackson (May 3, 1861 – January 10, 1952), also known as Honoré Jackson or Jaxon, was secretary to Louis Riel during the North-West Rebellion in Canada in 1885. He was married to Aimée, a former teacher in Chicago.

He was born in Toronto, Canada West, to a Methodist family, but several years later his family moved to Wingham, Ontario. Jackson later attended the University of Toronto for three years; however, due to his father's bankruptcy, he was unable to complete his last year. In 1881 he moved to Prince Albert in the North-West Territories' District of Saskatchewan, where he soon began to sympathize with the Métis and their struggle against the Canadian government, though he was not a Métis himself. Jackson became personal secretary to Louis Riel when Riel returned to Canada in 1884, and the two organized a Métis militia and planned a provisional government. Open fighting broke out between the disgruntled Métis and the North-West Mounted Police along with hastily raised militia on March 18 at Duck Lake.

That same day (18 March 1885), Jackson was baptized Catholic by Father Fourmond. Riel stood as godfather for the ceremony and gave him the name "Honoré Joseph Jaxon". The next day Riel declared the establishment of a provisional government (see Exovedate).

However, Jackson's mental health was affected by the religious event, and by the turmoil and excitement of open rebellion, and within days, Riel imprisoned Jackson, perhaps thinking he had gone insane but also fearing that his eccentric religious ideas and his support for Henry George's radical philosophical ideas against private ownership of land may cause discord within his (Riel's) followers. Later during the rebellion, Riel released Jackson.

He was captured when Canadian government troops overcame the last Métis resistance in the Battle of Batoche ending on May 12, 1885. He was tried for treason, but found not guilty by reason of insanity and sent to an insane asylum in Lower Fort Garry, near Winnipeg, Manitoba. He escaped the asylum on November 2 and fled to the United States.

Once there, he changed his name to Honoré Jaxon and joined the labour union movement in Chicago, Illinois, and was active in socialist circles as well. He also decided to lie about his identity and told others he was a Métis. In 1894 he was part of Coxey's Army, which marched to Washington, DC, to demand an eight-hour workday. In 1897 he converted to the Baháʼí Faith and oriented his concerns to Canada.

He returned to Canada briefly between 1907 and 1909, spending some of the time interviewing former participants of the Rebellion and addressing labour/socialist meetings. He returned to the United States, eventually moving to New York City. He collected books, newspapers, and pamphlets relating to the Métis people in an attempt to establish in their honour a museum in New York. However, years went by and he slipped into poverty and extreme old age. He was evicted from his apartment on December 12, 1951, and his collection (considered unimportant by the city) was sold as waste paper. He died a month later.

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

title: Honoré Jackson


text:
Airlock

An airlock is a room or compartment which permits passage between environments of differing atmospheric pressure or composition, while minimizing the changing of pressure or composition between the differing environments. "Airlock" is sometimes written as air-lock or air lock, or abbreviated to just lock.

An airlock consists of a chamber with two airtight doors or openings, usually arranged in series, which do not open simultaneously. Airlocks can be small-scale mechanisms, such as those used in fermenting, or larger mechanisms, which often take the form of an antechamber.

An airlock may also be used underwater to allow passage between the air environment in a pressure vessel, such as a submarine, and the water environment outside. In such cases the airlock can contain air or water. This is called a floodable airlock or underwater airlock, and is used to prevent water from entering a submersible vessel or underwater habitat.

Operation
The procedure of entering an airlock from the external or ambient pressure environment, sealing it, equalizing the pressure, and passing through the inner door is known as locking in. Conversely, locking out involves equalizing pressure, unsealing the outer door, then exiting the lock compartment to enter the ambient environment. Locking on and off refer to transfer under pressure where the two chambers are physically connected or disconnected prior to equalizing the pressure and locking in or out.

Before opening either door, the air pressure of the airlock chamber is equalized with that of the environment beyond the next door. A gradual pressure transition minimizes air temperature fluctuations, which helps reduce fogging and condensation, decreases stresses on air seals, and allows safe verification of critical equipment.

When a person who is not in a pressure suit moves between environments of greatly different pressures, an airlock changes the pressure slowly to help with internal air cavity equalization and to prevent decompression sickness. This is critical in underwater diving, and a diver or compressed air worker may have to wait in an airlock for a number of hours in accordance with a decompression schedule. A similar arrangement may be used for access to airtight clean spaces, contaminated spaces, or unbreathable atmospheres, which may not necessarily involve any differences in pressure; in these cases, a decontamination procedure and flushing are used instead of pressure change procedures.

19th century
The first airlock patent was granted in 1830 to Thomas Cochrane, who came up with the idea to help facilitate underground tunnel construction. It was put into use in 1879 during an attempt to dig a tunnel under the Hudson river.

20th century
The Apollo program involved developments in airlock technology, as airlocks are critical to allow humans to enter and exit the spacecraft while on the Moon without losing too much air due to its scant atmosphere.

During the 1969 Apollo 11 mission, there was no room that was primarily designed to be an airlock; instead, they used the cabin as an airlock. It had to be evacuated and depressurized before the door was opened, and then once the door was closed it had to be re-pressurized again before anyone could safely reenter the cabin without a space suit.

21st century
When the International Space Station (ISS) first began to house humans in November 2000, it did not include an airlock, and all extravehicular activity had to be facilitated by the airlock on the Space Shuttle until the Quest Joint Airlock module was installed in July 2001.

The first ever commercial space airlock was the Nanoracks Bishop Airlock, installed on the ISS in December 2020. It is "bell-shaped" and is designed to transfer payloads out from the ISS interior and into space. it is the largest airlock of its kind on the station, capable of fitting "payloads as large as a refrigerator."

Air environments
Airlocks are used in air-to-air environments for a variety of reasons, most of which center around either preventing airborne contaminants from entering or exiting an area, or maintaining the air pressure of the interior chamber.

One common use of airlock technology can be found in some cleanrooms, where harmful or otherwise undesired particulates can be excluded by maintaining the room at a higher pressure than the surroundings, alongside other measures. Conversely, particulates are prevented from escaping hazardous environments, such as nuclear reactors, laboratories of biochemistry, and medical centers, by keeping negative room pressure - maintaining the room at a lower pressure than the surroundings, so that air (and any particulates that it carries) cannot escape easily.

A lesser-known application of an airlock is in architecture: inflatable buildings and air-supported structures such as pressurized domes require the internal air pressure to be maintained within a specific range so that the structure doesn't collapse. Airlocks are generally the most cost-efficient way to allow people to enter and exit these structures.

Airlocks are utilized to maintain electron microscope interiors at near-vacuum so that air does not affect the electron path. Fermentation locks, such as those used in alcohol brewing, are a type of airlock which allow gases to escape the fermentation vessel while keeping air out. Parachute airlocks are necessary because airfoil collapse due to depressurization can result in dangerous loss of altitude.

Since the 1980s, airlock technology has been used to explore newly detected chambers in the Egyptian pyramids, to prevent the contents from beginning to decompose due to air contamination.

Underground
Civil engineering projects that use air pressure to keep water and mud out of the workplace use an airlock to transfer personnel, equipment, and materials between the external normabaric environment and the pressurized workplace in a caisson or sealed tunnel. The airlock may need to be large enough to accommodate a whole working shift at the same time.

Locking in is usually a quick procedure, taking only a few minutes, while the decompression required for locking out may take hours.

Underwater
Underwater applications include:
 * Hyperbaric chambers, to allow entry and exit while maintaining pressure difference between chamber and environment;
 * Submarines, closed diving bells, and underwater habitats that are not at ambient pressure, to permit divers to enter and exit. In submarines and underwater habitats they may also be called diver lock-out compartments; and
 * Torpedo tubes and escape trunks in submarines.

Saturation diving
In saturation diving, airlocks are crucial safety elements; they serve as pressurized gateways to safely manage the transfer of divers and support personnel between the saturation system (living quarters) and the diving bell, which shuttles divers to their underwater worksite.

Airlocks in saturation diving are equipped with safety features such as pressure gauges, manual overrides, and interlocks.

Saturation systems typically feature a variety of airlocks, including a stores lock for the transfer of supplies and a medical lock for secure passage of medical necessities or emergency evacuations. Complex "split-level" systems, which house divers at different pressure levels for varied work depths, may necessitate additional airlocks.

Decompression post-dive is a gradual process, often taking a full week. During this time, the airlocks allow divers to shift to a decompression chamber where pressure is progressively reduced back to surface levels. In emergencies, airlocks can facilitate transfer to a hyperbaric escape chamber or lifeboat without significant pressure changes.

Hyperbaric treatment chambers
In any hyperbaric treatment chamber capable of accommodating more than one person, and where it may be necessary to get a person or equipment into or out of the chamber while it is pressurized, an airlock is used. There will usually be a large airlock at the chamber entry capable of holding one or more persons, and a smaller medical lock for locking in medical supplies and food, and locking out waste.

Outer space
Airlocks are used in outer space, especially during human spaceflight, to maintain the internal habitable environment on spacecraft and space stations when persons are exiting or entering the spacecraft. Without an airlock (or similar technology, such as a suitport) the air inside would be rapidly lost upon opening the door due to the expansive properties of the gases that comprise breathable air, as described by Boyle's law. An airlock room is needed to decompress astronauts after they suit up in specialized space suits in preparation for extravehicular activity, and then to recompress them upon return. Airlocks such as the Nanoracks Bishop Airlock also allow payloads to be released into space with minimal air loss.

Other examples of airlocks used in space include the Quest Joint Airlock and the airlock on Kibō (ISS module).

title: Airlock


text:
Commutative property

In mathematics, a binary operation is commutative if changing the order of the operands does not change the result. It is a fundamental property of many binary operations, and many mathematical proofs depend on it. Perhaps most familiar as a property of arithmetic, e.g. "3 + 4 = 4 + 3" or "2 × 5 = 5 × 2", the property can also be used in more advanced settings. The name is needed because there are operations, such as division and subtraction, that do not have it (for example, "3 − 5 ≠ 5 − 3"); such operations are not commutative, and so are referred to as noncommutative operations. The idea that simple operations, such as the multiplication and addition of numbers, are commutative was for many years implicitly assumed. Thus, this property was not named until the 19th century, when mathematics started to become formalized. A similar property exists for binary relations; a binary relation is said to be symmetric if the relation applies regardless of the order of its operands; for example, equality is symmetric as two equal mathematical objects are equal regardless of their order.

Mathematical definitions
A binary operation $$*$$ on a set S is called commutative if $$x * y = y * x\qquad\mbox{for all }x,y\in S.$$ In other words, an operation is commutative if every two elements commute. An operation that does not satisfy the above property is called noncommutative.

One says that $x$ commutes with $y$ or that $x$ and $y$ commute under $$*$$ if $$ x * y = y * x.$$ That is, a specific pair of elements may commute even if the operation is (strictly) noncommutative.

Commutative operations

 * Addition and multiplication are commutative in most number systems, and, in particular, between natural numbers, integers, rational numbers, real numbers and complex numbers. This is also true in every field.
 * Addition is commutative in every vector space and in every algebra.
 * Union and intersection are commutative operations on sets.
 * "And" and "or" are commutative logical operations.

Noncommutative operations
Some noncommutative binary operations:

Division, subtraction, and exponentiation
Division is noncommutative, since $$1 \div 2 \neq 2 \div 1$$.

Subtraction is noncommutative, since $$0 - 1 \neq 1 - 0$$. However it is classified more precisely as anti-commutative, since $$0 - 1 = - (1 - 0)$$.

Exponentiation is noncommutative, since $$2^3\neq3^2$$. This property leads to two different "inverse" operations of exponentiation (namely, the nth-root operation and the logarithm operation), which is unlike the multiplication.

Truth functions
Some truth functions are noncommutative, since the truth tables for the functions are different when one changes the order of the operands. For example, the truth tables for $(A ⇒ B) = (¬A ∨ B)$ and $(B ⇒ A) = (A ∨ ¬B)$ are

Function composition of linear functions
Function composition of linear functions from the real numbers to the real numbers is almost always noncommutative. For example, let $$f(x)=2x+1$$ and $$g(x)=3x+7$$. Then $$(f \circ g)(x) = f(g(x)) = 2(3x+7)+1 = 6x+15$$ and $$(g \circ f)(x) = g(f(x)) = 3(2x+1)+7 = 6x+10$$ This also applies more generally for linear and affine transformations from a vector space to itself (see below for the Matrix representation).

Matrix multiplication
Matrix multiplication of square matrices is almost always noncommutative, for example: $$ \begin{bmatrix} 0 & 2 \\   0 & 1  \end{bmatrix} = \begin{bmatrix} 1 & 1 \\   0 & 1  \end{bmatrix} \begin{bmatrix} 0 & 1 \\   0 & 1  \end{bmatrix} \neq \begin{bmatrix} 0 & 1 \\   0 & 1  \end{bmatrix} \begin{bmatrix} 1 & 1 \\   0 & 1  \end{bmatrix} = \begin{bmatrix} 0 & 1 \\   0 & 1  \end{bmatrix} $$

Vector product
The vector product (or cross product) of two vectors in three dimensions is anti-commutative; i.e., b × a = −(a × b).

History and etymology

Records of the implicit use of the commutative property go back to ancient times. The Egyptians used the commutative property of multiplication to simplify computing products. Euclid is known to have assumed the commutative property of multiplication in his book Elements. Formal uses of the commutative property arose in the late 18th and early 19th centuries, when mathematicians began to work on a theory of functions. Today the commutative property is a well-known and basic property used in most branches of mathematics.

The first recorded use of the term commutative was in a memoir by François Servois in 1814, which used the word commutatives when describing functions that have what is now called the commutative property. Commutative is the feminine form of the French adjective commutatif, which is derived from the French noun commutation and the French verb commuter, meaning "to exchange" or "to switch", a cognate of to commute. The term then appeared in English in 1838. in Duncan Gregory's article entitled "On the real nature of symbolical algebra" published in 1840 in the Transactions of the Royal Society of Edinburgh.

Rule of replacement
In truth-functional propositional logic, commutation, or commutativity refer to two valid rules of replacement. The rules allow one to transpose propositional variables within logical expressions in logical proofs. The rules are: $$(P \lor Q) \Leftrightarrow (Q \lor P)$$ and $$(P \land Q) \Leftrightarrow (Q \land P)$$ where "$$\Leftrightarrow$$" is a metalogical symbol representing "can be replaced in a proof with".

Truth functional connectives
Commutativity is a property of some logical connectives of truth functional propositional logic. The following logical equivalences demonstrate that commutativity is a property of particular connectives. The following are truth-functional tautologies.

 * Commutativity of conjunction: $$(P \land Q) \leftrightarrow (Q \land P)$$
 * Commutativity of disjunction: $$(P \lor Q) \leftrightarrow (Q \lor P)$$
 * Commutativity of implication (also called the law of permutation): $$\big(P \to (Q \to R)\big) \leftrightarrow \big(Q \to (P \to R)\big)$$
 * Commutativity of equivalence (also called the complete commutative law of equivalence): $$(P \leftrightarrow Q) \leftrightarrow (Q \leftrightarrow P)$$

Set theory
In group and set theory, many algebraic structures are called commutative when certain operands satisfy the commutative property. In higher branches of mathematics, such as analysis and linear algebra the commutativity of well-known operations (such as addition and multiplication on real and complex numbers) is often used (or implicitly assumed) in proofs.

Mathematical structures and commutativity

 * A commutative semigroup is a set endowed with a total, associative and commutative operation.
 * If the operation additionally has an identity element, we have a commutative monoid
 * An abelian group, or commutative group is a group whose group operation is commutative.
 * A commutative ring is a ring whose multiplication is commutative. (Addition in a ring is always commutative.)
 * In a field both addition and multiplication are commutative.

Associativity
The associative property is closely related to the commutative property. The associative property of an expression containing two or more occurrences of the same operator states that the order operations are performed in does not affect the final result, as long as the order of terms does not change. In contrast, the commutative property states that the order of the terms does not affect the final result.

Most commutative operations encountered in practice are also associative. However, commutativity does not imply associativity. A counterexample is the function $$f(x, y) = \frac{x + y}{2},$$ which is clearly commutative (interchanging x and y does not affect the result), but it is not associative (since, for example, $$f(-4, f(0, +4)) = -1$$ but $$f(f(-4, 0), +4) = +1$$). More such examples may be found in commutative non-associative magmas. Furthermore, associativity does not imply commutativity either – for example multiplication of quaternions or of matrices is always associative but not always commutative.

Symmetry
Some forms of symmetry can be directly linked to commutativity. When a commutative operation is written as a binary function $$z=f(x,y),$$ then this function is called a symmetric function, and its graph in three-dimensional space is symmetric across the plane $$y=x$$. For example, if the function $A$ is defined as $$f(x,y)=x+y$$ then $$f$$ is a symmetric function.

For relations, a symmetric relation is analogous to a commutative operation, in that if a relation R is symmetric, then $$a R b \Leftrightarrow b R a$$.

Non-commuting operators in quantum mechanics
In quantum mechanics as formulated by Schrödinger, physical variables are represented by linear operators such as $$x$$ (meaning multiply by $$x$$), and $\frac{d}{dx}$. These two operators do not commute as may be seen by considering the effect of their compositions $x \frac{d}{dx}$ and $\frac{d}{dx} x$  (also called products of operators) on a one-dimensional wave function $$\psi(x)$$: $$ x\cdot {\mathrm{d}\over \mathrm{d}x}\psi = x\cdot \psi' \ \neq \ \psi + x\cdot \psi' = {\mathrm{d}\over \mathrm{d}x}\left( x\cdot \psi \right) $$

According to the uncertainty principle of Heisenberg, if the two operators representing a pair of variables do not commute, then that pair of variables are mutually complementary, which means they cannot be simultaneously measured or known precisely. For example, the position and the linear momentum in the $$x$$-direction of a particle are represented by the operators $$x$$ and $$-i \hbar \frac{\partial}{\partial x}$$, respectively (where $$\hbar$$ is the reduced Planck constant). This is the same example except for the constant $$-i \hbar$$, so again the operators do not commute and the physical meaning is that the position and linear momentum in a given direction are complementary.

Books

 * Abstract algebra theory. Covers commutativity in that context.  Uses property throughout book.
 * Linear algebra theory. Explains commutativity in chapter 1, uses it throughout.
 * Abstract algebra theory. Uses commutativity property throughout book.
 * Linear algebra theory. Explains commutativity in chapter 1, uses it throughout.
 * Abstract algebra theory. Uses commutativity property throughout book.
 * Abstract algebra theory. Uses commutativity property throughout book.
 * Abstract algebra theory. Uses commutativity property throughout book.

Articles

 * Article describing the mathematical ability of ancient civilizations.
 * Translation and interpretation of the Rhind Mathematical Papyrus.
 * Translation and interpretation of the Rhind Mathematical Papyrus.
 * Translation and interpretation of the Rhind Mathematical Papyrus.

Online resources

 * Krowne, Aaron,, Accessed 8 August 2007.
 * Definition of commutativity and examples of commutative operations
 * , Accessed 8 August 2007.
 * Explanation of the term commute
 * , Accessed 8 August 2007
 * Examples proving some noncommutative operations
 * Article giving the history of the real numbers
 * Page covering the earliest uses of mathematical terms
 * Biography of Francois Servois, who first used the term
 * Page covering the earliest uses of mathematical terms
 * Biography of Francois Servois, who first used the term
 * Biography of Francois Servois, who first used the term
 * Biography of Francois Servois, who first used the term

title: Commutative property


text:
Baschet Brothers

The Baschet Brothers were two French artists named François Baschet (born 30 March 1920, in Paris; died 11 February 2014) and Bernard Baschet (born 24 August 1917, Paris; died 17 July 2015 ) who collaborated on creating sound sculptures and inventing musical instruments, such as the Cristal Baschet. François Baschet was a sculptor and Bernard Baschet an engineer. The Baschet Brothers invented the inflatable guitar, the aluminum piano and many other experimental musical instruments. They created an "Baschet Educational Instrumentarium" for exposing young people to musical concepts.

The Baschet's research started in the 1950s artistic turmoil, soon turning the two brothers into the pioneers of sound sculpture, in addition to making them highly requested by musicians, composers, experimental directors.

The quest for new sounds led the Baschet brothers to combine new materials of the time, usually through folding metal sheets into geometric shapes. Their sculptures range from small folded sheet metal of a few centimeters up to structures several meters high with loud, impressive and complex sounds. Their exhibitions were shown in prestigious museums throughout the world – the United States, Japan, Germany – as well as in small villages in France, always with the aim of making art accessible to all.

The work of the Baschet brothers of making sound art accessible to all continues through the official association, established in 1982: the Baschet Sound Structures Association (originally "Structures sonores et pédagogie", it changed its name in 2012). The association has the support of the Baschet family and has an exclusive licence for creating some of the Baschet reproductible works.

Instruments
The Cristal baschet is a type of musical instrument designed by the Baschet brothers in the 1950s, the Cristal Baschet is played with wet fingers on glass rods. Its continuous, enchanting sounds have inspired many artists and composers. The current Cristal Baschet models produce a variety of sounds and can also be used in percussion. They can be fitted with numerous resonators including "moustaches" and different types of diffusers: cones and metal sheets.

The Rotating Whistler (“Le Sifflant Tournant”, created in 1962, produces the sharpest and longest sounds of all the Baschet Sound Structures. Turning the keyboard produces an unusual sound effect which does not need an amplifier cone.

Created in 1967, the Polytonal Percussion (“La Percussion Polytimbre”) includes large, straight rods that create deep, resonant sounds. The keyboard is organized with different percussive devices and cones diffuse the sound.

The Voice Leaf (“La Tôle à Voix”) was created in 1965 to mimic the Indian Tanpura, the metal sheets serve as resonators which transform the human voice when vibrated.

Public monuments
The Baschet brothers also created several public monuments such as clocks, fountains, bell towers and chimes – some ephemeral, some still in existence. One of the first fountains created was made for the World's Fair, in San Antonio Texas in 1968.

They made others in the early 1970s, including in Cologne, New York, Mexico City, London and Barcelona.

Subsequently, they worked on bell towers and clocks. The Baschet "signal sonore"(or school bell) of the Blaise Pascal school is in the process of being restored in Saint-Michel-sur-Orge – the town where Bernard Baschet's studio has been since 1970.

The Baschet Educational Instrumentarium
Invented in the 1980s, the Baschet Educational Instrumentarium consists of 14 sound structures which make a "sound palette" of around 100 different tones. Its purpose is to initiate children, adults and people with disabilities in collective musical discovery through games and experimentation, and without any previous musical knowledge.

Based on the large, original Baschet sound structures, the Baschet Educational Instrumentarium creates a broad spectrum of sounds, including those not in the classical European repertoire, as well as some which resemble electroacoustic sounds.

Education in sound culture is stimulated through listening to sounds, to oneself and to others. The experience of sound is not only through listening, it is also through hands-on learning and musical improvisation.

This Instrumentarium is also used in concert by musicians. There are approximately 500 Baschet Educational Instrumentariums in existence, in France and around the world.

Career
François had wanted to be an artist, but his father warned him against pursuing the unstable life of an artist. He decided to study business in college, but felt no passion for it. After World War II, which had interrupted his education, he decided to travel around the world. He brought with him on his trip a guitar to help him earn a living, but wanting something more portable he invented an inflatable guitar using a balloon and a collapsible wood neck. He continued to perform with this guitar upon his return to Paris. Soon he and his brother, who had studied engineering, began collaborating on sculptural musical instruments.

Beginning in 1952, the Baschets started research into all existing musical instruments and put this knowledge to work in creating dozens of structures sonores (i.e., 'sonorous sculptures'). Their visually striking instruments were crafted out of steel and aluminum and amplified by large curved conical sheets of metal, and are most often easy to play and accessible to people with any level of experience. One example of this is the Hemisfair Musical Fountain, which consists of an array of posts at the top of which are groups of conical sound diffusers, and above them circles of metal prongs. These are played by jets of water aimed by observers.

In 1954, the brothers met Jacques and Yvonne Lasry. Jacques was a pianist and composer and Yvonne was an organist. The four formed an association which they called "Lasry-Baschet Sound Structures." They held their first concerts in 1955. The group was successful and in 1960 were asked by Jean Cocteau to provide music for his film, Le Testament d'Orphée. The group toured, appearing on television shows including The Ed Sullivan Show. In 1966 they were invited to hold an exhibition at the Museum of Modern Art and director Alfred Barr purchased a sculpture for the museum's collection. Their tune "Manège" was also used as theme for the Granada TV program Picture Box, which ran in the United Kingdom from 1966 to 1990.

In the 1960s the Lasrys emigrated to Israel. In 1977 Bernard met Michel Deneuve, a musician, who joined them, starting a new association, and assisted in creating instruments. Deneuve was especially dedicated to working on their instrument called the "Cristal".

Discography

 * "Crystal", Michel Deneuve, the double album for sixty years of the birth of the Crystal. 2014
 * "Voyage autour du Cristal", Michel Deneuve, Rue Stendhal Distribution, new edition, 2013
 * "Danse de Dunes", Michel Deneuve, Rue Stendhal Distribution, new edition, 2013
 * Les Sculptures Sonores – The First Fifty Years, FMR Records, CD, 1999
 * 4 Espaces Sonores, with Bernard Baschet, Michel Deneuve and Alain Dumont, 1982
 * "Seize Nouvelles D'Ailleurs" (LP), Michel Deneuve, Sysmo Records, 1983
 * "L'Art Du Cristal" (LP), Michel Deneuve, Arion, 1984
 * Structures for Sound, Museum of Modern Art, 10" vinyl, 1965

title: Baschet Brothers


text:
User:Ram Moskovitz

Hey there,

You're at my user page on Wikipedia. Perhaps you want to know a bit about me.

My full name is Ram Austryjak Moskovitz and I was born in Tel-Aviv Israel on February 22, 1970.

I graduated from Florida International University in 1994 with a degree in Computer Science and I am a class of 1987 graduate of Gulliver Prep School in South Florida.

Amy Beth Levin and I married on September 4 2004 at the Squaw Creek Resort near Lake Tahoe California. It was a perfect day for our out-door wedding and a great time was had by all.

I worked at VeriSign (originally called DCI) since I left my role as an engineering consultant to RSA Data Security in April 1995. My long-time friend Jason Paul and I were the first two engineers at VeriSign; Jason had worked at RSA since mid 1991 and referred me to an interview at RSA. I worked there for about three months augmenting the engineering team and authoring the help and documentation for RSA's first end-user offering "RSA Secure" an automated file level encryption tool for Windows.

In my time at VeriSign I helped develop VeriSign's initial SSL Client and Server PKI certificate service platform as well as integration toolkits and glue code to stand up public LDAP service which work well with Outlook, OE, Mozilla, Thunderbird and others to enable the S/MIME based encryption that is built in. I played a major role in designing, developing, and rolling out our code security (shrinkrwap and authorization control) services including those which are the basis for Qualcomm's BREW, Microsoft's ActiveX, Netscape's Object Signing and quite a few others. I have also participated in the development and deployment of solutions for various US public agencies including DoD.

Having spent eight years building our Security Services division as a developer, technology lead, manager, and ultimately director I did a one year stint working in our CTO office on stragic technology evaluation and development. Following my time in the CTO office I joined our newly founded Corporate Strategy group for two years where I developed and drove support for new service concepts mostly relating to digital content into our executive team as well as our target customer base including studios, telcos, cable, and software technology companies. After two years in corporate strategy I was asked to transfer into our content services group and help to market and sell our new and existing services so I transfered in and completed the development and deployment of a demo showcasing the capabilities VeriSign has related to digital content.

After twelve fruitful years grinding away at VeriSign I decided to take a sabbatical to collect my thoughts and recenter before beginning the next phase of my career. Six months into my sabbatical VeriSign HR asked that I choose between coming back and leaving permanently so I quit! I took about eighteen months off by which time I was thoroughly bored and decided one day to both join a friend of mine starting a retail business as well as accept a position as CTO of an upstart financial services company with my brother Alex. Suffice it so say that I have not been bored since the day I started working again.

Quick update... The store with my friend Chris is called Simple Autosports while the company is called Simple Incorporated. Here is the ebay auto parts store The financial services company is called Association Financial Services (AFS)

If you want to reach me give me a call at the main number listed here.

Here is my linked-in profile.

title: User:Ram Moskovitz


text:
User talk:Ram Moskovitz

Hello there. If you're looking for my Wikipedia home page it's here http://en.wikipedia.org/wiki/User:Ram_Moskovitz

title: User talk:Ram Moskovitz


text:
Code Co-op

Code Co-op is the peer-to-peer revision control system made by Reliable Software.

Distinguishing features
Code Co-op is a distributed revision control system of the replicated type.

It uses peer-to-peer architecture to share projects among developers and to control changes to files. Instead of using a centralized database (the repository), it replicates its own database on each computer involved in the project.

The replicas are synchronized by the exchange of (differential) scripts. The exchange of scripts may proceed using different transports, including e-mail (support for SMTP and POP3, integration with MAPI clients, Gmail) and LAN.

Code Co-op has a built-in peer-to-peer wiki system, which can be used to integrate documentation with a software project. It is also possible to create text-based Wiki databases, which can be queried using simplified SQL directly from wiki pages.

Standard features

 * 1) Distributed development support through E-mail, LAN, or VPN
 * 2) Change-based model—modifications to multiple files are checked in as one transaction
 * 3) File additions, deletions, renames, and moves are treated on the same level as edits—they can be added in any combination to a check-in changeset
 * 4) File changes can be reviewed before a check-in using a built-in or user-defined differ
 * 5) Synchronization changes can be reviewed in the same manner by the recipients
 * 6) Three-way visual merge
 * 7) Project history is replicated on each machine. Historical version can be reviewed, compared, or restored
 * 8) Integration with Microsoft SCC clients, including Visual Studio

History
Code Co-op was one of the first distributed version control systems. It debuted at the 7th Workshop on System Configuration Management in May 1997.

The development of Code Co-op started in 1996, when Reliable Software, the distributed software company that makes it, was established. Reliable Software needed a collaboration tool that would work between the United States and Poland. The only dependable and affordable means of communication between the two countries was e-mail, hence the idea of using e-mail for the exchange of diffs. Of course, with such slow transport, using a centralized repository was infeasible. Each user of Code Co-op had to have a full replica of the repository, including the history of changes.

The problem was reduced to that of designing a distributed database that uses slow and unreliable transport for synchronization (later, faster LAN transport was also added). It also followed that the synchronization between multiple sites must use some kind of peer-to-peer protocol.

In 2018, the C++ source code for Code Co-op was released under the MIT License.

Theoretical foundations
Code Co-op is an example of a distributed database. Local repositories are considered the replicas of this virtual database. Each check-in corresponds to a distributed commit—a non-blocking version of a two-phase commit.

title: Code Co-op


text:
MacWrite

MacWrite is a WYSIWYG word processor application released along with the first Apple Macintosh systems in 1984. Together with MacPaint, it was one of the two original "killer applications" that propelled the adoption and popularity of the GUI in general, and the Mac in particular.

MacWrite was spun off to Claris, which released a major update in 1989 as MacWrite II. A further series of improvements produced 1993's MacWrite Pro, but further improvements were few and far between. By the mid-1990s, MacWrite was no longer a serious contender in the word processing market, development ended around 1995, and it was completely discontinued in 1998 due to dwindling sales.

Development
When the Mac was first being created, it was clear that users would interact with it differently from other personal computers. Typical computers of the era booted into text-only disk operating system or BASIC environments, requiring the users to type in commands. Some of these programs may have presented a graphical user interface of their own, but on the Mac, users would instead be expected to stay in the standard GUI both for launching and running programs. Having an approachable, consistent GUI was an advantage for the Mac platform, but unlike prior personal computers, the Mac was sold with no programming language built-in.

This presented a problem to Apple: the Mac was planned to be launched in 1983, with a new user interface paradigm, but no third-party software would be available for it, nor could users easily write their own. Users would end up with a computer that did nothing. In order to fill this void, several members of the Mac team took it upon themselves to write simple applications to fill these roles until third-party developers published more full-fledged software. The result was MacWrite and MacPaint, which shipped free with every Macintosh from 1984 to 1986.

The MacWrite development team was a company called Encore Systems, founded and led by Randy Wigginton, one of Apple's earliest employees, and included Don Breuner and Ed Ruder (co-founders of Encore Systems and also early Apple employees; Gabreal Franklin later joined Encore Systems as President.) Wigginton, who had left Apple in 1981, maintained a relationship with many Apple employees, many of whom were on the Macintosh development team. He agreed to lead the MacWrite development team on a semi-official basis. Before it was released, MacWrite was known as "Macintosh WP" (Word Processor) and "MacAuthor". Allegedly, Steve Jobs was not convinced of his team's abilities, and secretly commissioned another project just to be sure; its development was eventually released as WriteNow.

Early versions
The first versions of MacWrite were rather limited, supporting only the most basic editing features and able to handle just a few pages of text before running into performance problems. (Early versions of MacWrite held the entire document in memory, and early versions of the Macintosh had relatively little free memory.) Nevertheless, it increased user expectations of a word processing program. MacWrite established the conventions for a GUI-based word processor, with such features as a toolbar for selecting paragraph formatting options, font and style menus, and a ruler for tabs, margins, and indents. Similar word processors followed, including the first GUI version of Microsoft Word and WriteNow, which addressed many of MacWrite's limitations while adhering to much the same user interface.

The original Mac could print to a dot matrix printer called the ImageWriter, but quality was only adequate. The later LaserWriter laser printer allowed dramatically better output, at a price. However, the possibilities of the GUI/MacWrite/LaserWriter combination were obvious and this, in turn, spurred the development of desktop publishing, which became the "killer app" for the Mac and GUIs in general.

MacWrite's inclusion with the Macintosh discouraged developers from creating other word processing software for the computer. Apple unbundled the software with the introduction of the Macintosh Plus, requiring customers to purchase it for the first time. Strong sales continued, and Apple eventually let MacWrite and MacPaint languish with no development resources assigned to improving them.

Unfortunately this plan backfired. Users flooded Apple with complaints, demanding newer versions that would keep pace with new features in the Mac, while at the same time developers flooded Apple with complaints about there being any possibility of an upgrade. Apple finally decided the only solution was to spin off the products as a separate company, Claris.

MacWrite II
Claris formed in 1987 and re-released the existing versions of the Apple products under their own name. Initially it seemed Claris was as uninterested in developing MacWrite as Apple had been. Several minor upgrades were released to allow MacWrite to run on newer versions of the classic Mac OS, but few other problems were addressed.

Things changed in the later 1980s with the introduction of MacWrite II. The main changes for this release were an updated user interface, a number of new "style" capabilities, and the inclusion of Claris' file translator technology, XTND. MacWrite II was the first really new version of the software, and was based on a word processing engine purchased from Quark, Inc.

By 1989 Word already dominated the Mac with about 60% market share, but the introduction of MacWrite II changed things dramatically; by 1990 Word had dropped to about 45% of the market, and MacWrite had risen to about 30%. This seemed to demonstrate that it would be worth developing further, but Claris did not respond quickly with updated versions.

Microsoft, on the other hand, did, and soon introduced Word 4.0. MacWrite's share once again started to erode.

MacWrite Pro
In the late 1980s, Claris started a massive upgrade series to produce the "Pro" line of products. The main change would be to integrate all of their products with a consistent GUI based on that of FileMaker. This included a common toolbar running down the left side of the screen, and a number of standardized tool palettes. In addition, the Pro series also used common international spelling dictionaries and a thesaurus. The result was a suite of products that all look and work the same way, and are able to read and write each other's formats.

The resulting MacWrite Pro, released in early 1993, was a major upgrade from previous versions. Reviewers almost universally praised the new release as offering all the required tools while still being very easy to use. However, development had been slow; one developer claimed it was primarily due to extremely demanding quality assurance requirements. By the time MacWrite Pro was released, Word completely dominated the word processor market. Pro did little to address MacWrite's rapidly dwindling market share, which briefly stabilized at about 5% of the market before starting to slide again. Sales were apparently dismal, and it was one of the first products Claris abandoned in the mid-1990s.

The word-processing module of AppleWorks was very similar to MacWrite Pro. While it was written entirely from scratch, it retained some of the design limitations of MacWrite Pro. However, later versions of AppleWorks are unable to read older MacWrite Pro files.

Reception
In a survey of five Macintosh word processors, Compute!'s Apple Applications in 1987 wrote that "once a bold pioneer, MacWrite now seems frozen in time ... it lags behind other word processors in power and responsiveness, and it's clearly unsuited for outlining, layout, and other advanced tasks".

title: MacWrite


text:
Talk:Helen Garner

Critical reception
From the article

 * Critics in her home country Australia are divided as to the merit of Garner's work. Mainstream publications regard her as one of Australia's finest writers, but underground thinkers dismiss her work entirely.

Would you like to cite some evidence for the claim about "underground thinkers"? I know that The First Stone made her persona non grata amongst some feminists, but the article's claim is considerably wider. --Robert Merkel 00:58, 12 Aug 2003 (UTC)

The First Stone
To the non-logged in contributor from Melbourne University who originated this article, I have decided to split off a seperate article on The First Stone. If I recall correctly, the criticism of the book was considerably more multi-pronged than what was stated, and a more complete analysis would be more appropriate for a seperate article IMO.

By the way, have you considered getting an account here? You can use a pseudonym if you want. --Robert Merkel 07:19, 13 Aug 2003 (UTC)

'La Mama: The Story of a Theatre' edit
Cosmolino edited: Non-fiction writing - 'removed incorrext attribution of a book'. I assume good faith about Cosmolino's edit. OK, so it is a fact that Garner is not the sole author of the book. However - see the results of a Google of 'Jones Burstall Garner "La Mama"' - if Garner is not considered a co-author, she's at least a named contributor to the book. Cosmolino's edit also muddled a few links - fixed them. --Shirt58 13:37, 31 March 2007 (UTC)

Suggestions please
If there is anyone out there looking at this article I'd be interested in ideas re how to structure it. Garner's career is so diverse and she has been attended by such controversy (and varied opinion) that it is hard to work out how best to organise an article about her. I'm happy to do more work on it, but I wonder how best to proceed. I also suspect that more of her books should have their own pages - particularly MONKEY GRIP, JOE CINQUE'S CONSOLATION.Sterry2607 (talk) 02:26, 25 April 2008 (UTC)
 * I agree that the novels and non-fiction works need pages of their own. Separating these out might allow you to see the rest of the page more clearly.  Just a thought. Perry Middlemiss (talk) 07:14, 2 May 2008 (UTC)

 * Thanks Perry...I'll try to get back to it in a week or two and see what I can do.Sterry2607 (talk) 10:07, 2 May 2008 (UTC)

True Stories: Selected Non-fiction
I own this book and have been studying it at school. It's very interesting and contains a lot of information regarding the backstory behind many of her works and thoughts on writing. When I get around to it I may make an article/edit some articles to incorporate this. Avnas Ishtaroth drop me a line  03:49, 30 July 2008 (UTC)

Photo required?
A BOT has added a category tag indicating that this article no longer requires a photo. This is not the case as no photo of the author is present in the main article. I'm removing the catgeory tag as a result. -- Perry Middlemiss (talk) 00:37, 14 April 2009 (UTC)

External links modified
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title: Talk:Helen Garner


text:
Billy Strayhorn

William Thomas Strayhorn (November 29, 1915 – May 31, 1967) was an American jazz composer, pianist, lyricist, and arranger who collaborated with bandleader and composer Duke Ellington for nearly three decades. His compositions include "Take the 'A' Train", "Chelsea Bridge", "A Flower Is a Lovesome Thing", and "Lush Life".

Early life
Strayhorn was born in Dayton, Ohio, United States. His family then moved to the Homewood neighborhood of Pittsburgh, Pennsylvania. His mother's family came from Hillsborough, North Carolina, and she sent him there to protect him from his father's drunken rages. Strayhorn spent many months of his childhood at his grandparents' house in Hillsborough. In an interview, Strayhorn said that his grandmother was his primary influence during the first ten years of his life. He became interested in music while living with her, playing hymns on her piano and listening to records on her Victrola record player.

Return to Pittsburgh and meeting Ellington
Strayhorn returned to Pittsburgh while still in grade school. He worked odd jobs to earn enough money to buy his first piano, and took lessons from Charlotte Enty Catlin. He attended Westinghouse High School, later also attended by jazz pianists Erroll Garner and Ahmad Jamal. He played in the school band, and studied under Carl McVicker, who had also instructed Erroll Garner and Mary Lou Williams. He studied classical music for a time at the Pittsburgh Music Institute, writing a musical, forming a trio that played daily on a local radio station, and writing/composing the songs "Life Is Lonely" (later renamed "Lush Life"), "My Little Brown Book", and "Something to Live For". By age 19, he was writing for a professional musical, Fantastic Rhythm.

Strayhorn's original ambition to become a classical composer was foiled by the harsh reality of a black man trying to make it in the classical world, which at that time was almost completely dominated by white people. Strayhorn was introduced to the music of pianists like Art Tatum and Teddy Wilson at age 19. The artistic influence of these musicians guided him into the realm of jazz where he remained for the rest of his life. His first jazz exposure was in a combo called the Mad Hatters that played around Pittsburgh. Strayhorn's fellow students, guitarist Bill Esch and drummer Mickey Scrima, also influenced his transition to jazz, and he began writing arrangements for Buddy Malone's Pittsburgh dance band after 1937.

Strayhorn saw Duke Ellington play in Pittsburgh in 1933, then met him in December 1938 after Ellington performed there again. He first explained, and then showed the bandleader how he would have arranged one of Ellington's own pieces. Ellington was impressed enough to invite other band members to hear Strayhorn. At the end of the visit, he arranged for Strayhorn to meet him when the band returned to New York. Strayhorn worked for Ellington for the next 25 years as an arranger, composer, occasional pianist and collaborator until his death from cancer. As Ellington described him, "Billy Strayhorn was my right arm, my left arm, all the eyes in the back of my head, my brain waves in his head, and his in mine."

Working with Ellington
Strayhorn was a gifted composer and arranger who seemed to flourish in Duke's shadow. Ellington was arguably a father figure and the band was affectionately protective of the diminutive and mild-mannered Strayhorn, nicknamed by the band "Strays", "Weely", and "Swee' Pea". Ellington used Strayhorn to complete his thoughts and introduce new musical ideas (and sometimes it worked the other way around), while giving him the freedom to write on his own and enjoy at least some credit. Though Duke Ellington took credit for much of Strayhorn's work, he did not maliciously drown out his partner. Ellington would make jokes onstage like, "Strayhorn does a lot of the work but I get to take the bows!" On the other hand, Ellington did not oppose his publicists frequently crediting him without any mention of Strayhorn, and, despite the latter's attempts to hide his dissatisfaction, "Strayhorn revealed", at least to his friends, "a deepening well of unease about his lack of public recognition as Ellington's prominence grew."

Strayhorn composed the Duke Ellington orchestra's signature song, "Take the 'A' Train", and a number of other pieces that became part of the band's repertoire. In some cases Strayhorn received attribution for his work such as "Lotus Blossom", "Chelsea Bridge", and "Rain Check", while others, such as "Day Dream" and "Something to Live For", were listed as collaborations with Ellington or, in the case of "Satin Doll" and "Sugar Hill Penthouse", were credited to Ellington alone. Strayhorn also arranged many of Ellington's band-within-a-band recordings and provided harmonic clarity and polish to Duke's compositions. Ellington gave Strayhorn full credit as his collaborator on later, larger works such as Such Sweet Thunder, A Drum Is a Woman, The Perfume Suite, and Far East Suite, where Strayhorn and Ellington worked closely together. Strayhorn often played the piano with the Ellington orchestra, both live and in the studio.

Detroit Free Press music critic Mark Stryker concludes that the work of Strayhorn and Ellington in the score of the 1959 Hollywood film Anatomy of a Murder is "indispensable, [although] ... too sketchy to rank in the top echelon among Ellington-Strayhorn masterpiece suites like Such Sweet Thunder and Far East Suite, but its most inspired moments are their equal." Film historians have recognized the soundtrack "as a landmark—the first significant Hollywood film music by African Americans comprising non-diegetic music, that is, music whose source is not visible or implied by action in the film, like an on-screen band." The score "avoided the cultural stereotypes that previously characterized jazz scores and rejected a strict adherence to visuals in ways that presaged the New Wave cinema of the '60s."

In 1960, the two collaborated on arrangements for the album The Nutcracker Suite, recorded for Columbia Records and featuring jazz interpretations of "The Nutcracker" by Tchaikovsky. The original album cover is notable for the inclusion of Strayhorn's name and picture along with Ellington's on the front.

Personal life
Shortly before going on his second European tour with his orchestra, from March to May 1939, Ellington announced to his sister Ruth and son Mercer Ellington that Strayhorn "is staying with us." Through Mercer, Strayhorn met his first partner, African-American musician Aaron Bridgers, with whom Strayhorn lived until Bridgers moved to Paris in 1947.

As an adult, Strayhorn was openly gay to his friends and the members of the Ellington band. He participated in the civil rights movement, and as a friend to Martin Luther King Jr., he arranged and conducted "King Fit the Battle of Alabam'" for the Ellington orchestra in 1963 for the historical revue (and album) My People, dedicated to King.

Strayhorn had a major influence on the career of Lena Horne, who wanted to marry Strayhorn and considered him the love of her life. Strayhorn used his classical background to improve Horne's singing technique, and they recorded songs together. In the 1950s, Strayhorn left Duke Ellington for a few years to pursue a solo career of his own. He released a few solo albums and revues for the Original Copasetics and took on theater productions with his friend Luther Henderson.

Illness and death
In 1964, Strayhorn was diagnosed with esophageal cancer, which took his life in the early morning of May 31, 1967, when he was with his partner, Bill Grove, not in Lena Horne's arms as has often been falsely reported. By her own account, she was touring in Europe when she received the news of Strayhorn's death. His ashes were scattered in the Hudson River by a gathering of his closest friends.

While in the hospital, he submitted his final composition to Ellington; "Blood Count" was used as the third track in Ellington's memorial album for Strayhorn, ...And His Mother Called Him Bill, which was recorded several months after Strayhorn's death. The last track of the album is a solo version of "Lotus Blossom" performed by Ellington, who sat at the piano and played it while the band (who can be heard in the background) were packing up after the formal end of the recording session.

Legacy
A Pennsylvania state historical marker highlighting Strayhorn's accomplishments was placed at Westinghouse High School in Pittsburgh, from which he graduated. In North Carolina, a highway historical marker honoring Strayhorn is located in downtown Hillsborough, near his childhood home. Strayhorn is also memorialized in a mural in Downtown Hillsborough.

The former Regent Theatre in Pittsburgh's East Liberty neighborhood was renamed the Kelly-Strayhorn Theater in honor of Strayhorn and fellow Pittsburgh resident Gene Kelly in 2000. It is a community-based performing arts theater.

In 2015, Strayhorn was inducted into the Legacy Walk.

In his autobiography and in a spoken word passage in his Second Sacred Concert, Ellington listed what he considered Strayhorn's "four major moral freedoms": "freedom from hate, unconditionally; freedom from self-pity (even through all the pain and bad news); freedom from fear of possibly doing something that might possibly help another more than it might himself and freedom from the kind of pride that might make a man think that he was better than his brother or his neighbor."

Discography
For albums where Strayhorn arranged or performed with the Duke Ellington Orchestra see Duke Ellington discography

As leader/co-leader

 * 1950-51 Great Times! with Duke Ellington (Mercer, 1964)
 * 1958 !!!Live!!! (Roulette, 1958)
 * 1959 Cue for Saxophone (Felsted, 1959)
 * 1961 The Peaceful Side (United Artists, 1963)
 * 1964-65 Lush Life (Red Baron, 1992)

As arranger

 * 1961 Johnny Hodges with Billy Strayhorn and the Orchestra (Verve, 1962)

As sideman
With Johnny Hodges
 * Castle Rock (Norgran, 1955) – recorded in 1951
 * Creamy (Norgran, 1955)
 * Ellingtonia '56 (Norgran, 1956)
 * Duke's in Bed (Verve, 1956)
 * The Big Sound (Verve, 1957)
 * Blues A-Plenty (Verve, 1958)
 * Not So Dukish (Verve, 1958)

With Joya Sherrill
 * Joya Sherrill Sings Duke (20th Century Fox, 1965)

With Ben Webster
 * Music for Loving (Norgran, 1954)

title: Billy Strayhorn


text:
Talk:Paleoclimatology

Source for graph "Holocene Temperature Variations"
The article doesn't state any reference for this graph, or for anything in that section. — Preceding unsigned comment added by 220.244.53.102 (talk) 21:46, 5 January 2020 (UTC)

New diagrams
The Diagram of the global temperatures is out of date. There are new diagrams from Scotese (2021).

https://eprints.whiterose.ac.uk/169823/1/Scotese_etal_phan_temp_AAM.pdf Sciencia58 (talk) 19:43, 4 January 2024 (UTC)

Wiki Education assignment: Principles of Biology 2
— Assignment last updated by QualifiedPOB2 (talk) 16:09, 8 April 2024 (UTC)

title: Talk:Paleoclimatology


text:
ImageWriter

The ImageWriter is a product line of dot matrix printers formerly manufactured by Apple Computer, Inc., and designed then to be compatible with their entire line of computers. There were three different models introduced over time, which were popular mostly among Apple II and Macintosh owners.

Original ImageWriter
The first ImageWriter is a serial-based dot matrix printer introduced by Apple Computer in late 1983.

The printer was essentially a re-packaged 9-pin dot matrix printer from C. Itoh Electronics (model C. Itoh 8510, with a modified ROM and pinout), released the same year. It was introduced as a replacement for the earlier parallel-based Apple Dot Matrix Printer/DMP (also a C. Itoh model) and, while primarily intended for the Apple II, worked across Apple's entire computer product line. The ImageWriter could produce images as well as text, up to a resolution of 144 DPI and a speed of about 120 CPS (characters per second). In text mode, the printer was logic-seeking, meaning it would print with the head moving in both directions while it would print only in one direction for graphics and Near Letter Quality. The ImageWriter was also supported by the original Macintosh computer, the Macintosh 128K. Apple wanted a graphical printer for the Mac, and had introduced the ImageWriter primarily to support the new machine. This permitted it to produce WYSIWYG output from the screen of the computer, which was an important aspect for promoting the concept of the GUI and, later, desktop publishing. The ImageWriter could be supported by Microsoft Windows-based PC's by using the included C. Itoh 8510 compatible driver.

The ImageWriter was succeeded by the ImageWriter II in late 1985.

A wider version of the ImageWriter, sold as ImageWriter 15", was introduced in January 1984. It allowed printing to 12" wide as well as to 15" wide paper. This version of ImageWriter remained in production for more than a year after the ImageWriter II was introduced. Production was eventually discontinued in January 1987.

Accessories
In 1984 Thunderware introduced the ThunderScan, an optical scanner that was installed in place of the ImageWriter ribbon cartridge. With support for the Apple II and the Mac, the ThunderScan provided low cost grayscale scanning with moderate resolution and speed.

ImageWriter II
The ImageWriter II is a serial based dot matrix printer that was manufactured by Apple Computer, which supported its entire computer product line when it was released in September 1985. It had several optional add-ons available, including: a plug-in network card, buffer memory card, and motorized sheet feeder. It also supported color printing with an appropriate ribbon. The codename for the ImageWriter II was "Express"

Compute! reported in 1989 that many believed that the ImageWriter II was inferior to its predecessor. The magazine stated that the first ImageWriter was sturdier, handled paper better, and had better print in most cases.

Features
The ImageWriter II, like its predecessor, used a 9-pin C. Itoh mechanism. However, the ImageWriter II was significantly faster in draft mode, where it could print 250 characters per second. Color images and text could be produced by using a color ribbon, and eight colors were supported by the original version of QuickDraw on the Macintosh despite running on a monochrome platform. On the Apple II, complex full-color graphics could be printed. Used with the appropriate software, the ImageWriter II could produce color images with potentially hundreds of simulated colors through dithering.

The ImageWriter II offered three ASCII text-quality modes:
 * NLQ (near-letter-quality) at 45 CPS, a feature for very high text quality on the Apple II platform or for improved draft printing quality on the Macintosh platform.
 * Standard (Correspondence) mode at 180 CPS, providing average-quality text.
 * Draft mode at 250 CPS, the fastest output but at the lowest quality level.

In addition to having the same ASCII and European-language characters found in the original ImageWriter, the ImageWriter II added 32 MouseText characters.

The ImageWriter II was designed in accordance with Apple's Snow White design language. In 1986, it received the I.D. Design Review and Silver International Design Excellence Awards, making it the first desktop printer to receive such approbation.

Add-on accessories
The printer had an expansion socket under the front cover which could accommodate either Apple's AppleTalk network card or 32K memory buffer card, but not both at the same time. Sequential Systems produced a 2-in-1 solution card that combined both features into one card, as well as larger memory buffer cards up to 1 MB. With an optional AppleTalk networking card installed, it was a low-cost alternative to the vastly more expensive LaserWriter. Another third-party innovation was an add-on peripheral called the ThunderScan, which allowed the printer to work as a low-cost optical scanner (in which the scanner mechanism temporarily replaced the ink ribbon cartridge).

The ImageWriter II also supported an optional motorized sheet feeder that could feed cut-sheet paper.

Revisions

 * The original Imagewriter II (1985) closely followed Apple's Snow white design introduced with the Apple IIc, and was one of the few peripherals that matched its creamy off-white color scheme known at Apple as Fog. This model is recognizable for being white in color and not having the product name on the front cover. There were many ROM revisions produced for this and later ImageWriter IIs, made visible through a self-test (pressing the form feed button while turning the ImageWriter on, then releasing both buttons simultaneously; the printer would then print the ROM version as well as dipswitch settings). The printer came with a small built-in 2K RAM memory buffer, with option to expand.
 * The second ImageWriter II (1986) changed to the standard warm-grey Apple "Platinum" color. This model is not only recognizable for being light grey in color, but for having the product name printed beside the rainbow Apple logo. It was introduced at roughly the same time as the Apple IIGS in late 1986, to match its then-new Platinum color scheme which was later adopted by all other computers at Apple.
 * The third revision, the ImageWriter II/L (1990) as it was known internally, offered some slight design improvements. The internal power source changed to a switching power supply, reducing the overall weight of the printer by 10 pounds. As a result of the change, power and serial interface ports were moved from the legs to either ends of the tractor-feed housing. This model also increased the built-in buffer memory to 24K RAM, eliminating the need for the memory-expansion option. The expansion socket was still present for supporting an optional AppleTalk network card.

The ImageWriter II was compatible with Microsoft Windows-based computers using the operating systems' included C-Itoh 8510 driver, while color support was available through third-party drivers. The only requirement was an available serial port and appropriate interface cable.

Despite the introduction of the inkjet StyleWriter in 1991, the ImageWriter II kept selling. It continued in production until late 1996, making it the longest-running Apple product in history.

In popular culture
On the 2000 album A Spectrum of Infinite Scale, surf-rock band Man or Astro-man? included the song "A Simple Text File". The song is a recording of the sound of an ImageWriter II printing a carefully crafted file.

An ImageWriter can also be seen the music video for Marilyn Manson's "The Dope Show."

ImageWriter LQ
ImageWriter LQ (Letter Quality) is a 27-pin dot matrix printer introduced in 1987 by Apple Computer, Inc. The print quality was comparable to competing 24-pin dot-matrix printers, and offered graphics at 320 × 216 DPI. Guaranteed compatibility with both Apple II and Macintosh computers made it popular in schools.

The LQ had more options than any of the other Apple dot-matrix printers, including:
 * ImageWriter II/LQ LocalTalk Option card or 32K memory buffer card
 * Cut Sheet Feeder ($299 USD)
 * Additional paper bins ($169 USD, each - maximum of 2) for the sheet feeder
 * Envelope Feed for the sheet feeder ($49 USD)
 * SCSI interface (not released)

Color ribbons were $149 for a box of six.

title: ImageWriter


text: This Might Be A Wiki

title: This Might Be A Wiki