Canon

Star Wars canon was first defined in the first issue of the Lucasfilm magazine, the Star Wars Insider:


 * "Gospel, or canon as we refer to it, includes the screenplays, the films, the radio dramas and the novelisations. These works spin out of George Lucas' original stories, the rest are written by other writers. However, between us, we've read everything, and much of it is taken into account in the overall continuity. The entire catalog of published works comprises a vast history -- with many off-shoots, variations and tangents -- like any other well-developed mythology."

Canon and Expanded Universe
This policy has been further refined and fleshed out over the years. The STAR WARS website also details the role of canon, Expanded Universe, or "EU" sources, and how they fit into overall STAR WARS continuity. Chris Cerasi stated,


 * "When it comes to absolute canon, the real story of Star Wars, you must turn to the films themselves - and only the films. Even novelizations are interpretations of the film, and while they are largely true to George Lucas' vision (he works quite closely with the novel authors), the method in which they are written does allow for some minor differences. The novelizations are written concurrently with the film's production, so variations in detail do creep in from time to time. Nonetheless, they should be regarded as very accurate depictions of the fictional Star Wars movies.


 * The further one branches away from the movies, the more interpretation and speculation come into play. LucasBooks works diligently to keep the continuing Star Wars expanded universe cohesive and uniform, but stylistically, there is always room for variation. Not all artists draw Luke Skywalker the same way. Not all writers define the character in the same fashion. The particular attributes of individual media also come into play. A comic book interpretation of an event will likely have less dialogue or different pacing than a novel version. A video game has to take an interactive approach that favors gameplay. So too must card and roleplaying games ascribe certain characteristics to characters and events in order to make them playable.


 * The analogy is that every piece of published Star Wars fiction is a window into the 'real' Star Wars universe. Some windows are a bit foggier than others. Some are decidedly abstract. But each contains a nugget of truth to them. Like the great Jedi Knight Obi-Wan Kenobi said, 'many of the truths we cling to depend greatly on our point of view."

As of 2000, Lucas Licensing has appointed Leland Chee to create a continuity tracking database referred to as Holocron continuity database. As with every other aspect having to do with the overall story of Star Wars, the Holocron follows the canon policy that has been in effect for years, but the capabilities of database software allowed for each element of a story, rather than the stories themselves, to be classified on their own merits.

Canon priority
The Holocron 's database field is divided into 4 levels: G-canon, C-canon, S-canon, and N-canon. G, C and S together form an overall continuity. Each ascending level overrides the lower ones. e.g. Boba Fett's back story was radically altered with the release of Attack of the Clones, forcing retconning of older source material to fall in line with the new G-canon back story.

G-canon is absolute canon; the movies and anything coming directly from George Lucas (including unpublished production notes from him or his production department that are never seen by the public). Elements coming directly from Lucas in the movie novelizations, reference books, and other sources are also G-canon, though anything created by the authors of those sources is C-canon (see below).


 * The remastered editions are deemed superior to the theatrical ones, since they correct miastakes and improve consistence between the Trilogues. They also express Lucas' original intention and also final word. 

C-canon is pretty much everything in the Expanded Universe; Star Wars books, comics, games, cartoons, and more. Games are a special case as generally only the stories are C-canon while things like stats and gameplay may not be.

S-canon is "secondary" canon; the story itself is considered non-continuity, but the non-contradicting elements are still a canon part of the Star Wars universe. This includes things like the popular online roleplaying game Star Wars Galaxies and certain elements of a few N-canon stories.

N-canon is "non-canon". What-if stories (such as stories published under the Star Wars: Infinities label), some game stats, and anything else directly contradicted by higher canon ends up here. N-canon is the only level that is not considered canon by Lucasfilm.