What is Canon?
The term "canon" is occasionally referred to by the people who make Star Trek, and much more often by the fans and here at EAS. The usefulness of the canon is under permanent debate, as are the interpretations what has to be regarded as canonical and what not. This write-up attempts to clarify what canon actually is, why it exists, how we can handle moot cases and how the canon policy at EAS works.
General definition of canon
The word "canon" has more than one meaning in the English language. Several definitions can be found on the disambiguation page at Wikipedia (see the latest version of "Canon" at Wikipedia). The following two are relevant for the assessment of the Star Trek canon:
"A list of books accepted by an ecclesiastic communion as authoritative or divinely inspired. The term was originally Christian, referring to books declared divinely inspired by the canons of Church councils..."
"In fiction, the officially authorized interpretation of characters and events. In fandom, the term is often used to distinguish between 'canonical' accounts (i.e. those authorized by the copyright holder) and those of fan fiction, sometimes called fanon..."
As we can easily imagine, the word originally used for the "divinely inspired" literature of Christian churches has been passed on to describe the valid parts of a fiction. In this sense canon stands for what we could find in the history books or other records of the fictional universe. Certainly the canonical fictional universe is not supposed to be as authoritative as the teachings of a church. Nonetheless, there are many parallels.
Side note "Canon" is a noun, the correct adjective would be "canonical". Yet, it has become quite common to use "canon" as an adjective like in "It is canon that all Vulcans can meld their minds." This is how the word is often used here at EAS too, although "canonical" would be correct in this example.
This is the practical explanation of canon as it could be found at the official Star Trek website until 2006:
"As a rule of thumb, the events that take place within the real action series and movies are canon, or official Star Trek facts. Story lines, characters, events, stardates, etc. that take place within the fictional novels, the Animated Series and the various comic lines are not canon.
There are only a couple of exceptions of this rule: the Jeri Taylor penned novels 'Mosaic' and 'Pathways'. Many of the events in these two novels feature background details of the main Star Trek: Voyager characters. (Note: There are a few details from an episode of the Animated Adventures that have entered into the Star Trek canon. The episode 'Yesteryear', written by D.C. Fontana, features some biographical background of Spock.)"
Many of these positions, especially those concerning TAS and Jeri Taylor's novels, sound like they were arbitrarily made up and are debatable, as will be pointed out later. But the key statement is that only "events within the real action series" are canon, and at least that much is generally accepted. This definition of canon encompasses the five live action TV shows (TOS, TNG, DS9, Voyager, Enterprise) and the now eleven movies, all in the versions in which they were on TV or in the theaters, respectively.
Side note The notion that any books could be canonical is contested by writers posting at the TrekBBS. Paramount's policy that Jeri Taylor's novels should be canon is said to be non-existent and may have been made up just for the fans.
From 2006 to 2010 the following more elaborate explanation could be found at startrek.com:
"As a rule of thumb, the events that take place within the live-action episodes and movies are canon, or official Star Trek facts. Story lines, characters, events, stardates, etc. that take place within the fictional novels, video games, the Animated Series, and the various comic lines have traditionally not been considered part of the canon. But canon is not something set in stone; even events in some of the movies have been called into question as to whether they should be considered canon! Ultimately, the fans, the writers and the producers may all differ on what is considered canon and the very idea of what is canon has become more fluid, especially as there isn't a single voice or arbiter to decide. Star Trek creator Gene Roddenberry was accustomed to making statements about canon, but even he was known to change his mind.
In the publishing world, there used to be two exceptions to the novel rule: the Jeri Taylor-penned books 'Mosaic' and 'Pathways.' Many of the events in these two novels feature background details of the main Star Trek: Voyager characters and were to be considered as references by writers on the show. Now that the show is over, some of those events may never be incorporated into a live action format, so the question of whether details from these novels remain canon is open to interpretation.
With regard to the Animated Series, there are a few details from the episode 'Yesteryear,' written by D.C. Fontana, that reveal biographical background on Spock and planet Vulcan. Details from this episode have been successfully incorporated into the canon of Star Trek (such as in 'The Forge') and now that the Animated Series is out on DVD, we hope that even more can make its way in!"
Note that the definition is overall watered down. While the canonicity of some events in the movies (obviously because of fan reactions to "Star Trek V") is suddenly questioned, TAS is said to be slated to become canon (following a fan vote at startrek.com). Another article at the site confirms this intention, and the TAS DVD special features even assure the viewers of the full canonicity of the series. Something of further interest is that at startrek.com suddenly canon is stated to be a question of if and when something from the previously non-canon realm is incorporated into a canon series. Thispractice may work out well for the people who make Star Trek, and in its ultimate consequence it would remove the need to care about canon at all. But it makes the decision if and where to draw a line increasingly complicated for the archivists and hence essentially for the fans.
Canon vs. official
In a simple approach it may seem that anything about the fictional Star Trek Universe that is officially released by Paramount should be automatically canonical. But with the word "official" being rather used as an administrative term and "canon" as a purely fictional quality the two are different. While Paramount Pictures may *officially* endorse books or games of their licensees, this does not imply that these products are *canon* too. On the contrary, as will be explained further down, Paramount keeps licensed products strictly non-canon.
This is merely the negation of "canon". If only live action is to be taken into account, then Star Trek novels, no matter if written by licensed authors or by fans, are never canon. In order to avoid misunderstandings: The designation "non-canonical" does not imply that they are badly written or that faithful fans should not read them. It just says that they are not a part of the canonical Star Trek Universe and are therefore irrelevant in its assessment. All novels, comics, reference books, calendars, role playing games, computer games, websites, TV shows outside the five series, merchandising items and everything else dealing in any way with Star Trek is non-canon, regardless of its origin or authorship.
Fans are occasionally referring to accounts whose canonicity is debatable as "apocryphal". The Wikipedia (see the latest version of "Apocryphal" on their server) defines the term like this:
"In Judeo-Christian theologies, apocrypha refers to religious Sacred text that have questionable authenticity or are otherwise disputed. When most in the Western world refer to the Apocrypha, they are typically referring to the 14 books excluded from Protestant Bibles..."
In Star Trek fandom, the term "apocryphal" represents any information that is not canon in a narrow sense, but is by some treated like or accepted as canon. This may include The Animated Series, the books by Jeri Taylor, reference books or deleted scenes. However, accounts from the live series, which are canon by their very definition, shouldn't be declared "apocryphal" just because some doubt its canonicity - even if there is an according allusion in the FAQ at startrek.com.
This word is obviously a combination of "fandom" and "canon". The Wikipedia (see the latest version of "Fanon" on their server) says about "fanon":
"Fanon is a fact or ongoing situation in fan fiction stories related to a television program, book, movie, or video game that has been used so much by fan writers that it has been more or less established as having happened in the fictional world, but it has not actually been established as having happened on the show, book or movie itself. Fanon is a portmanteau word of fan and canon..."
So "fanon" denotes views and opinions that are non-canon but widespread in fan fiction. Examples include minutiae like Uhura's first name Nyota, which was never mentioned on screen until 2009, or the notion that Romulans did not have warp drive in 2266, which is just a perpetuated misconception, as can be seen in the article about Warp Drive and Romulan History. More examples along these lines are listed on the page about False Canon.
These words are often used to denote accounts which are either not canon in its entirety or whose canonicity remains debatable. The latter could be described as "apocryphal" too.
Parts of fandom or of licensed literature that are in irreconcilable contradiction to canon facts may be called "anti-canon". In a discussion dealing just with canon facts it is irrelevant whether non-canon evidence may help or obstruct the assessment. But when reading (fan) fiction it is obvious that a knowledgeable fan may accept non-canon facts but will not appreciate it as soon as it becomes anti-canon.
Completely vs. partly canon
The suggestion that particular episodes or even parts of an episode, like suggested in the more recent FAQ at the official site, should be considered canon or non-canon opens a can of worms. Where could we possibly draw a line?
This term can be found very often in discussion forums or on personal websites. Many fans have decided to include additional works (such as TAS, novels or even fan fiction) to their so-called "personal canon", or they deny parts of the franchise their otherwise definite status as canonical (like some purists disregard Enterprise or even everything that came after TOS and the first six movies). A "personal canon" may and is supposed to be more consistent than the official canon and may contribute to a "fanon". Yet, owing to its arbitrary nature and limited validity a "personal canon" usually obstructs the assessment of canon accounts.
The reasons for the existence of an ecclesial canon are diverse. It is debatable whetherit was created in the first place to defy heretics who might take away power and prosperity from the official church, or whether it was first of all a honest matter of faith. Regarding the Star Trek Universe, the canon has a relatively harmless impact on the lives of most fans and it certainly is not intended by TPTB to control the fans. Still, there must be reasons for creating a canon of the Star Trek Universe.
Canon and continuity
As outlined in the article on the Realism of (Science) Fiction, Star Trek is designed as a TV series with internal consistency, as opposed to shows that are frequently rebooted or even take pleasure in creating deliberate continuity errors. During The Original Series' three seasons from 1966 to 1969 there was no obvious canon policy, like there was no particular attention to inter-episode continuity either. But as the fictional universe kept growing, it was necessary to come up with rules what has to be taken into account by future writers (the canon), as well as with a collection of such canon data for reference (The Star Trek Encyclopedia and a possible forerunner that may have existed behind the scenes for already some time).
Keeping events in new episodes compliant with canon has become a quality mark of the show.
Canon and creativity
Canon may be seen as an obstacle to creativity, simply because not all possibilities are allowed to be exploited. On the other hand, in a creative process canon boils down to a simple list of what has been done before and what not. This is not really a creative limitation. On the contrary, it can help avoid rehashes. Surely there is always a risk that writers consciously recycle plots just because they think it is a good idea to show familiar situations already established in the canon. Still, they better closely base their stories on canon events than just on clichés.
The knowledge about canon may even have a quite beneficial impact on storylines. A prominent example is DS9: "Trials and Tribble-ations" with its slavish adherence to the canon events of TOS: "The Trouble with Tribbles". Another one is the Vulcan arc of ENT: "The Forge", "The Awakening" and "Kir'Shara" that successfully removes a previous continuity error concerning Vulcan Mind Melds from canon. These episodes are commonly said to be among the most creative and most enticing installments of all Star Trek.
Canon and commerce
Star Trek takes place in many different forms, among which the TV series and movies are the center of interest. In addition, Trek-themed novels or computer games are available as well as typical merchandising items such as action figures, t-shirts and coffee mugs. Any company intending to sell anything with "Star Trek" printed on it needs a license from the brand owner Paramount Pictures, and this franchise makes up the major part of the business today.
Paramount is giving away the valuable name of Star Trek to various third-party products, and they certainly have an interest that these products adhere to certain standards. In an extreme (and fortunately fabricated) example we may think of a company that wants to produce a game featuring a boxing fight between Jean-Luc Picard and Darth Vader. Clearly both Paramount and Lucasfilms would protest against such a misuse of parts of their fictional universes. Most novels and games on the market are certainly not such an utter crap, and still they are non-canon. But this is only the ultimate consequence, considering that Paramount as a company strives to protect not only their financial interests but also to have full control of their own creative base.
There is actually an even more important reason why Paramount does not want any licensed products, especially those of literary relevance (novels and games) to be canon. If Paramount decided to adopt anything that was not originally created by an employee but by a contractor, they might have to pay royalties for each and every mention of this character or concept! So the Kzinti species from The Animated Series (TAS: "The Slaver Weapon") never found its way into any of the live series. The episode involving the Kzinti was written by Larry Niven, closely based on one of his novels (The Soft Weapon). Niven was irritated when Dean Foster wrote the novelization of the episode instead of himself, although he contradicts the common rumor that he threatened legal actions against Paramount (interview at Trekplace). Nevertheless it seems that Paramount preemptively banned the Kzinti from canon Star Trek, as well they prohibited their use in licensed works in at least three cases (Kzinti at Memory Alpha). Still, it was planned to finally include them in the fifth season of Enterprise. Another, even more prominent example is the character of T'Pol, who was named T'Pau in the draft of the series. But TPTB cautiously changed it to T'Pol in order to avoid the due credit to the author of TOS: "Amok Time", Theodore Sturgeon, in every episode. T'Pau was eventually included in the Vulcan arc on Star Trek Enterprise, though.
Canon and practicability
Star Trek writers are expected to be creative and not perfect librarians (something that is largely left to the fans today after Richard Arnold and later the Okudas used to fill that role). With 600 hours of TV it is already extremely hard to come up with stories that are original and still not in contradiction to previous installments. Without the help of the Encyclopedia and other reference works as well as of their colleagues and editors a writer would find himself lost in a confusing maze of facts that must be taken into account. This would become many times as complicated if they additionally had to take into account all novels. All of them because where could a line be drawn? And what about the games? They establish many facts as well. At some point it wouldn't be possibly any longer to insert new data because the adventures would fill many lifetimes of characters or ships, with incalculable inconsistencies.
Canon and the fans
As already mentioned, the term "canon" shows up on fan websites a lot more frequently than on startrek.com or in official reference works. Even casual viewers who may not be aware of the word "canon" care more about it than the studio could hope for. They notice goofs like the epitaph "James R. Kirk" because everyone knows that his true name is "James T. Kirk". They wonder if the contents of novels or comics may have any bearing on the TV series. They compare Star Trek with other franchises like Marvel Comics where the establishment of a common canon is practically impossible because of lacking continuity. In this regard the canon policy gives the fans, and especially the die-hard Trekkers who have seen every episode preferably several times, something to chew on. It allows to limit discussions among fans to a reasonable common ground, and it ultimately enables the setup of websites like Memory Alpha, which would be a bottomless pit without the canon foundation, and of EAS, which would become utterly pointless. In this sense the canon allows Star Trek to earn a "meta quality" when fans take care of episodes that the production staff has long finished and almost forgotten.
As already mentioned in the introductory note, the criteria for what type of evidence is canonical are under permanent discussion. Moreover, Gene Roddenberry and his successors are said to have included additional material to the canon, as well as they purportedly removed some of the live action from the canon. It will be discussed in the following whether the debated material should be regarded as canon, and whether the said exceptions are useful. The views in this section reflect the canon policy at EAS; other fan-made websites may arrive at slightly different conclusions, now that the official site more or less explicitly declares that canon is much a matter of interpretation, and especially in the wake of the controversial movie "Star Trek (2009)".
Novels and games
Only televised Star Trek is canon. This explicitly excludes books, and above all the myriad of novels based on Star Trek. None of them are canon in the view of Paramount, although many of them would fit into the timeline and would be largely free of anti-canon notions. The above mentioned royalty issue forbids (or makes it very unlikely) that characters established in the books ever find their way into canon Trek. The same applies to all Trek-themed games and other merchandise.
There can't be any exception along the lines "But these are soooo popular" or "She is such an excellent writer" or "He has been working on the series for years". Sorry, but any discussion of canon facts at EAS is strictly off-limits for accounts from novels and games.
Novels based on movies
The circumstances seem to be different if a novel is directly based on a feature film, written by the same author and usually more comprehensive than the movie. One prime example is the novelization of "Star Trek: The Motion Picture" by Gene Roddenberry, adding many facts and aspects that can't be found in the movie. If much of the book's content is canon because it describes the events on the screen, shouldn't the rest be canon too?
Novelizations are a different format than movies; they leave possible additional facts to our imagination. Here we can and we should draw a line because the canon would become incoherent if events on screen and in print were supposed to be somehow combined. Novelizations are disregarded at EAS.
Novels by Jeri Taylor
The two novels Mosaic and Pathways are explicitly mentioned on the official Star Trek website to be canon, the reason being that Jeri Taylor, at that time co-producer of the series, added essential background information on the Voyager main characters. But can this statement be maintained, considering that Voyager writers have been ignoring the novels? If they should have looked up facts there but actually didn't do it, the canonicity of her two books is only theoretical, and some smaller parts may be even anti-canonical.
The two books are well-written and might deserve to be canon, but seeing how the Voyager creative staff have been ignoring them, EAS is not bound to their facts either. The FAQ (until 2010) at the official website confirms my stance that the theoretical canonicity of the two novels is pointless as long as there are no interlinks with canon Trek and leaves the question open to interpretation.
The Animated Series
Gene Roddenberry is said to have TAS decanonized, but this is uncertain. The official website previously stated that it is non-canon without giving reasons. The Star TrekEncyclopedia and all other official manuals written since the late 1980s (since the canon exists) have not included references from The Animated Series. Nonetheless TAS may be treated as canon in the future according to the TAS DVD and the official site (until 2010), at least partly because of a fan vote at startrek.com. Yet, the official website also states that the canonicity of TAS, even if it is earned effortlessly, must be gradually confirmed by referring to events from TAS in future incarnations of Star Trek.
So far EAS strictly complied with TPTB's stance that TAS was non-canon. Now that the official policy may have been amended, I feel unable to promptly conform once again. This would not only mean for me to dig for new information in the series, which would be still the fun part, but it would require me to sift through the whole site and reconsider countless conclusions. TAS has been largely isolated for the past 25 years, and some facts will remain irreconcilable with the five live-action series. Especially due its nature as a show conceived for children and the often lacking quality of the production it often even doesn't allow to apply the same criteria. It gives TAS a different, usually lower weight than the live-action series in my view. These are the reasons why TAS will remain in a "proto-canon" limbo as far as my site is concerned. It will gradually appear in side notes and in separate sections, but evidence from live-action Trek will generally supersede accounts from TAS. As soon as a new Star Trek series heavily references events from TAS and hence TAS fulfills the criterion of being linked with everything else as outlined at startrek.com, I may reconsider this solution. In any case, while TAS does not exactly rank among my favorite incarnations of Trek, the TAS policy at EAS is first and foremost a technical necessity.
This particular TAS episode (review) is commonly regarded as the best of the whole series. But its quality alone should not be the reason to include it to the canon, especially considering the problems of partially canonical accounts. The actual reason cited for TAS: "Yesteryear" being canonical is that it adds to the background of Spock's character. While this is true and is quite useful, it is still no reason why these facts should be made canonical and other events from TAS not. Moreover, if canonicity were just a matter of quality or of usefulness, disappointed fans could turn the tables and demand that mishaps like "Star Trek V" or VOY: "Threshold" be declared non-canon.
At EAS I would have no problem accepting this one episode, but I see neither a particular reason for it nor would it have any palpable impact to treat it differently.
Star Trek V & VI
It may be just a rumor that Gene Roddenberry wanted these two movies removed from canon, allegedly because they don't reflect the true spirit of Star Trek. We may have to wonder anyway why Roddenberry was so opposed to the alleged racism in "Star Trek VI" (according to director Nicholas Meyer), a movie that came into the theaters after his death, that he condemned it before it was even completed.
Unless a confirmed statement by Gene Roddenberry is available, EAS will continue to regard these movies as canonical. And even if the ban is authentic, I see no reason to suddenly decanonize essential parts of the Star Trek Universe, irrespective of the silliness of "Star Trek V". With the official site implicitly acknowledging fans' moaning about "Star Trek V", we may be up to a surprising change of mind, but not on my part.
Star Trek Reboot
It was the intention of producer and director J.J. Abrams and his staff to reboot the franchise while respecting Star Trek's continuity. "Star Trek (2009)" takes place a few years before The Original Series, but establishes an entirely new timeline. It would be possible for the "Abramsverse" to be fully canon. At least, this is the official position.
The new movie is set in a different continuity that is incompatible with that of the rest of Star Trek. This, however, is no reason why it shouldn't be canon, just like the Mirror Universe of "Mirror, Mirror" too. The new movie will remain somewhat confined at EAS because I don't want to mingle the different timelines. But thinking further about it, even the USS Kelvin, a ship that must already have existed in the old continuity, and several other things are very hard to reconcile with Star Trek as we knew it. This is why I put "Star Trek (2009)" and everything that will follow in the Abramsverse in its entirety into a proto-canon limbo at EAS, in a similar way as The Animated Series. I am aware that this may "stigmatize" the movie, but I have huge issues with the changes made to just everything in "Star Trek (2009)", not just with its history and technology but also with the characters and storylines. I may eventually decide to separate the Abramsverse completely from Star Trek as it existed until 2009.
Star Trek: Countdown and Nero
These two comic series are tied into the the story "Star Trek (2009)". In an interview with Trekmovie.com, dated 9 December 2008, "Star Trek (2009)" writer Bob Orci said that he personally considered some novels canon, but that it is not up to him to declare Countdown canon. In a later Q&A session, dated May 22, 2009, he explained the inconsistencies between the movie "Star Trek (2009)" and Countdown with the comic being non-canon. The same applies to the Star Trek: Nero comics and the whole story about Nero's imprisonment on Rura Penthe.
The two comic series are ignored at EAS, just as all Trek comics and all novelizations of Trek movies. I don't expect them to ever gain official canon status, and even then the movie would have to be given precedence.
Books are non-canon because of their printed nature, even those officially released by Paramount via Pocket Books and with people working on the show as authors (reviews).The TNG Technical Manual and the DS9 Technical Manual can be regarded as apocryphal because a good deal of them consists of facts that supplement the scarce technical information given in the series itself and that were expected to be an official guideline for the writing staff too. The Star Trek Encyclopedia extracts data from the canon episodes. Where it is correct, it is a reproduction of canon facts, but not canon by itself. Even a few occurrences of False Canon can be found in the Encyclopedia.
So why does EAS take data from official reference books into account, especially from the TNG Technical Manual, the DS9 Technical Manual and the Star Trek Encyclopedia, although they are non-canon? Obvious examples are the registries of many ships of the Constitution class, some class names of the TNG era that were never mentioned on screen and some details about warp drive and other technology. The difference between these reference works and the novels is not immediately obvious. However, the novels are entering a competition with the episodes because they both tell stories, while the TNGTM is a book that we could find on Geordi's desk. The manual adds information that can be included into the realm of canon without major efforts, and without envisioning characters and environments like they are described in a novel or shown in an episode. Moreover, but this is just a practical consideration, in technical Trek discussions it is very useful to have some basics nailed down like the existence of a primary deuterium tank on a starship, even if they are never mentioned in the series.
Star Trek Technical Manual
Prior to TNG the STTM (review) was commonly regarded as official, yet no one called it "canon" back then. Its author, Franz Joseph Schnaubelt, had the blessing of Gene Roddenberry to write a technical manual of Star Trek, which consisted just of TOS in 1975. So Franz Joseph went ahead and created a manual consisting partially of schematics of canon devices, rooms, uniforms which he supplemented with what we would call fan fiction today, namely the Federation Charter, emblems of alien civilizations and the ship schematics.
Even if we attempt to establish an exception, the STTM as a whole fails to fulfill the requirements for canon data in several respects. First of all, a definition of canon didn't technically exist when the STTM was written. And as unfair as it may seem, just when Roddenberry set up the canon policy for TNG, the STTM was not included.
Side note Some time prior to TNG, they didn't get along with each other any longer, and it is said that Roddenberry intentionally laid out technical specs of TNG so as to disparage Franz Joseph's work - but this doesn't really belong here. If you would like to know more about Franz Joseph's background, please visit Trekplace.
Secondly, no printed publication, not even the technical manuals by Sternbach or Okuda, are regarded as canon themselves, but at most as apocryphal. Thirdly, certain major parts of the manual are of a debatable nature or are anti-canon, like the alien emblems, the map of the galaxy, the Federation Charter (actually a mostly literal rip-off of the UN Charter) and the circuit schematics of the tricorder etc. I simply wouldn't want to include these just to have a couple of more ships on the list.
The STTM is certainly non-canonical. Here at EAS it is not regarded as apocryphal either for several technical and practical considerations. Few single aspects of the book are canon though, simply because ship schematics from the STTM were used in "Star Trek II". But this certainly doesn't imply that the ships that can be glimpsed in the movie are exactly what they are meant to be in the book, much less that the vast number of names and registries printed there are "authentic".
Fandom reference books
Unlike the at least apocryphal TNG Technical Manual, the DS9 Technical Manual and the Star Trek Encyclopedia, publications like those of FASA, Jackill or Todd Guenther are unquestionably non-canon, as is the Spaceflight Chronology too. The same applies to some more recent books like Star Trek Star Charts (review) or The Starship Spotter. From Paramount's viewpoint they fall into the same category as novels, even if some depictions from FASA manual made it into TNG episodes. But this must be seen rather as an accident because the Art Department is usually quite careful not to include copyrighted material.
Fandom tech manuals are ignored at EAS the same way they are ignored by Paramount. Moreover, I don't see why a printed or a commercial fan fiction should be in any way more valuable than a free one on the web such as The Starfleet Museum.
The Klingon language devised by James Doohan for the first feature film consisted of just a few incoherent words and was later developed to a fully-fledged language by linguist Mark Okrand. Applying the same criteria to the language as to anything else in Star Trek, only the Klingon spoken on screen is canon (regardless of its consistency and of Okrand's involvement), not the complete grammar and vocabulary created by Okrand.
There is no need to define a more elaborate canon policy here at EAS as I don't speak Klingon. If I did, the language reference (The Klingon Dictionary) written by Mark Okrand would be regarded as an official reference like the TNG Technical Manual.
This is an interesting point to be considered because some of the behind-the-scenes information is widely accepted without actually being canonical. For instance, the Miranda class was never called by that name in any episode, not even in a screenplay. Still, it has become the commonly accepted name of the ship class thanks to the Star Trek Encyclopedias (well, until some time ago rivaled by the fandom name "Avenger class"). Fundamentally, behind-the-scenes information as it can be found in official reference manuals is just as apocryphal as these books are in their entirety.
Practical reasons require that some apocryphal information is treated as if it were canon. Otherwise long-standing facts like the name "Miranda class" would have to be dropped and replaced with something indefinite. We can be absolutely sure that, if the class name should ever be mentioned on screen, it will be Miranda.
Like with information from behind the scenes, most shooting scripts include additional lines or annotations that find their way into fandom. We certainly need to disregard them as soon as they are contradicted by canon facts. This happens with the so far common notion that the Klingon BoP in "Star Trek: The Search for Spock" was actually a Romulan vessel. The Klingon retro-BoPs in ENT: "Expanse" is the ultimate proof that there is no Romulan link. In some other cases there were little facts, especially names in scripts that were not mentioned on screen.
Some of the apocryphal extra information in scripts is taken into account at EAS. The policy is still not completely settled on this issue, but essentially EAS accepts just names and dates, not concepts. For instance, the Klingon shuttlepod from ENT: "Broken Bow" is called "K'toch class" in the EAS database because it was in the script. On the other hand, Saavik's half-Romulan origin is ignored even though it was hinted at in the script of "Star Trek: The Search for Spock".
Cut scenes/additional scenes
Were Picard and Data drinking wine in "Nemesis" or not? The DVD has an additional scene which is not in the theatrical version. Moreover, this scene is not embedded into the very movie track, but separate. The same question, with a more definite impact, crops up in "Star Trek: The Undiscovered Country". The scenes with Colonel West were cut from the movie, but inserted into later releases. So does he exist at all? And what about Kirk's orbital skydiving in "Generations", which was only available in the internet so far, not on DVD?
Without forgetting about the original versions, EAS generally takes into account additional or changed scenes if they were included in a way to form a new and improved version of the movie, most obviously in the case of "Star Trek: The Motion Picture" (new Vulcan landscape and V'ger's revised diameter in the Director's Cut). On the other hand, anyone who can rip a movie could easily insert unused scenes that were kept separately to where they belong, but we are obviously not supposed to view the movies like that. The decision what to take into account is the same as with the already mentioned script contents and remains somewhat arbitrary.
TOS and TNG Remastered
Whilst the producers have reassured that nothing is being changed in the storylines, the remastering (TOS-R) of The Original Series still stirs up continuity issues. The remastered version comes with improved effects such as of phaser shots, with new planetscapes and with new vessels too. TOS-R is designed to be more internally consistent. But which is correct: the old phaser beams that were occasionally red, or the new consistently blue ones? The old blurry planets, or the new highly detailed ones? Note that, once again, the question what is canon should not be primarily about quality or taste. The same question arises with the remastered version of TNG (TNG-R), although here the changes are less extensive.
This case is similar as with the Director's Cut of "Star Trek: The Motion Picture". Only the extent of the retcons in TOS-R is overall much larger. There are certainly TOS purists who only accept the episodes the way they always were (although Roddenberry would probably have been the last person not to try to improve its look). But even if the old TOS is hammered in stone, there is no reason why the remastered version shouldn't be equally valid. In other words, EAS treats both as canon. In practice, TOS-R can often be interpreted as a more realistic or more complete depiction of the very same places and events as in TOS without any trouble (unless we insist on the Enterprise having a mechanical clock as seen in TOS: "The Naked Time" or Earth being completely cloudless as in TOS: "Tomorrow is Yesterday"). Still, occasionally the visuals of TOS were amended more extensively, like the "flying dildo" of TOS: "Spock's Brain", which was replaced with a "pod ship" in TOS-R. In these cases I will give TOS precedence. Whenever new facts from the remastered version become available, there is a disambiguation at EAS like "In the original version... whereas in remastered TOS...". Additionally, facts from the remastered version will be tagged with an according symbol. The same applies to TNG-R.
Many fans tend to disregard silly or otherwise disagreeable events like the DS9 version of the Mirror Universe or even the whole series Star Trek Enterprise. Some assert that these take place in alternate universes and should be discarded as non-canon. The official canon policy, however, makes no difference between such "unreal" and "real" events. Even the content of dreams is canonical in the sense that it is visible on screen.
There is no point in declaring anything non-canon because it doesn't happen in "our" Star Trek Universe. The fact that there are different timelines has to be reflected by splitting up timelines, not by a-priori omission of "parallel" events.
Their canon nature doesn't prevent information from the live action series from sometimes being contradictory. This may happen because of negligent writing but also in case of conscious retcons. In many cases the contradictions may be explained away rather easily. But by no means such speculation should itself be declared canon, although fans are tempted to believe into the validity of their favorite hypothesis. Actually much of the fanon came to life as such conjectural explanations. A prominent example of contradictory canon is the Trill Problem, a fundamental revision of the nature of this race that defies a complete explanation.
Contradictory canon still is canon. It can be discussed which version is "more correct" and explanations can be worked out using more or less conjecture, but that doesn't change anything about their canonical nature. Needless to say that the views and theories on such problems presented here at EAS are non-canon.
Ex Astris Scientia
No, I'm not suffering from megalomania. The reason why I'm listing EAS as a candidate for a canon source is that some fans refer to my website as canon. But actually EAS does not create any canon content. It can only convey canon data and, in debatable cases, suggest reasonable solutions with a minimum of speculation.
A request: Visitors are advised never to mention anywhere that something written at EAS is "canon". At most it can be a quote or a picture from a canon episode or movie.
The real world
Is the real world canonical in Star Trek? The question wouldn't occur in a galaxy far, far away. But since Star Trek aims to depict the very future of humanity, its past has to be taken into account. The real world influences Star Trek by providing historical side notes, character and ship names and locations on Earth. In this sense the real world is definitely canonical, although Star Trek sometimes alters the course of human history or even the laws of physics. As long as the fictional events are set far enough in the future, there is no danger of our real world becoming "non-canon". The article on 21st Century Earth History demonstrates what happens if this precondition is not given.
Clearly the real world is taken into account in the assessment of the fictional universe here at EAS. But I don't go as far as including real-world events or real-world spaceships to the databases at this site. This would be rather pointless, considering that there are numerous websites or books that provide a deeper and more comprehensive account of the real world.
Canon Policy @ Memory Alpha
There are good reasons for a canon policy - at the Paramount lot as well as here at EAS. But fans shouldn't go as far as accepting only canon - because they know the Okudas' Encyclopedia by heart or because they just refuse to see that Trek can be anything else. On the other hand, there is the kind who stir up canon and fandom at will - because they either don't know that much and believe anything they see or read or because they don't want their creativity be limited by the strict yet contradictory canon of TPTB. I have encountered lots of either type of fans and any shade in between.
One typical situation is that some people in a message board explicitly talk about the number of nacelles on canon starships and someone throws in that the Federation class and Saladin class (from Franz Joseph's Star Fleet Technical Manual) are odd-nacelled. The result is a fruitless discussion about the definition of "canon", about the authority of Roddenberry, Okuda, Paramount or Pocket Books, about books which should be considered canon because they are written by Jeri Taylor, about Colonel West and the Starfleet Marines, and so on. Very often ideas of False Canon are involved too. This is one more reason why a well-established canon is a useful reference.
The canon policy at EAS accepts the definition of canon given by TPTB as the easiest way to avoid unnecessary discussions. Actually, I would go as far as saying that EAS couldn't exist without the canon because if there were not one supposedly true and authentic version of the fictional universe, it would become utterly pointless to file and analyze anything about it beyond a mere list what happened in which episode or book. In contrast to websites that are based on a "personal canon", EAS neither ignores canon accounts at the outset nor adds non-canon information. EAS includes some apocryphal reference works only if these fill in necessary details that would never be mentioned in an episode. This doesn't mean that EAS slavishly follows the interpretations put forth in reference works.
But canon is not everything. Every fan should feel encouraged to include whatever he likes to his personal view (not "personal canon") of the Star Trek Universe. That's what I'm doing with my ship designs, the ASDB and the Starfleet Museum too. I would never want to miss the fan-made stuff all around the planet because they really enrich the universe, no matter if I "believe" in their existence. I probably can't help those who don't even want to see anything that has not the seal of Paramount on it or the other extreme group, those who don't care about the idea of Star Trek and are turning Starfleet into a military organization with big-gunned warships. For anyone in between, canon is a common ground. Everything else is left to our imagination and tolerance or better, mutual understanding. There are always possibilities!
The Realism of (Science) Fiction - whether Star Trek is really "bordering on silliness"
False Canon - accounts which are incorrectly regarded as canonical in fandom or in official Trek
The Problems of Canonizing TAS - dealing with possible continuity and compatibility issues
Star Trek (2009): Reboot or Multiverse? - thoughts on the continuity and the canon status of the movie
Dealing with Continuity Issues of the Abramsverse - general thoughts and the policy at EAS
Some screen caps from TrekCore. Some ideas, especially concerning cut scenes, script information and other moot cases, were inspired by an article at Green Mole. Thanks also to the people at the SCN for discussing issues of canon. Thanks to Andrew Briggs for pointing me to the reason for Gene Roddenberry to condemn "Star Trek VI", to Kobi for correcting some facts about the Kzinti and to Spike for the revision of the alleged official canon policy.