Storing the revisions as full text is wasteful. We could just store the differences between the revisions. Typical diff algorithms you might know from version control system only deal with per-line differences. For natural text this is not very useful. We want to see character by character changes.
If you wonder what "character by character changes" mean, try the demo here: http://neil.fraser.name/software/diff_match_patch/svn/trunk/demos/demo_diff.html.
Mention http://mozilla.org/rhino/ScriptingJava.html and other resources
Download the zip file and extract the java file "java/diff_match_patch.java" into a new directory "./lib" in our wiki directory. Then compile the java file with (I assume you have a Java Development Kit installed!)
$ javac diff_match_patch.java
// FIXME to be continued