What can I do to prevent write-write conflicts on a wiki-style website?

Question

On a wiki-style website, what can I do to prevent or mitigate write-write conflicts while still allowing the site to run quickly and keeping the site easy to use?

The pr

Answer 1

Three-way merging: The first thing to point out is that most concurrent edits, particularly on longer documents, are to different sections of the text. As a result, by noting which revision Users A and B acquired, we can do a three-way merge, as detailed by Bill Ritcher of Guiffy Software. A three-way merge can identify where the edits have been made from the original, and unless they clash it can silently merge both edits into a new article. Ideally, at this point carry out the merge and show User B the new document so that she can choose to further revise it.

Collision resolution: This leaves you with the scenario when both editors have edited the same section. In this case, merge everything else and offer the text of the three versions to User B - that is, include the original - with either User A's version in the textbox or User B's. That choice depends on whether you think the default should be to accept the latest (the user just clicks Save to retain their version) or force the editor to edit twice to get their changes in (they have to re-apply their changes to editor A's version of the section).

Using three-way merging like this avoids lock-outs, which are very difficult to handle well on the web (how long do you let them have the lock?), and the aggravating 'you might want to look again' scenario, which only works well for forum-style responses. It also retains the post-respond style of the web.

If you want to Ajax it up a bit, dynamically 3-way merge User A's version into User B's version while they are editing it, and notify them. Now that would be impressive.