In-line visualization of content age

Question

I have two tables, pages and revisions. Revisions has a foreign key to a page. The contents of a page is the latest entry in the revisions table for that page. The revisions are full copies of the contents, no deltas.

As an experiment, I would like to visualize the revision state of the current revision. If text is new in the current revision, don't do anything. If it is from a recent revision, give it a green background color. If it's very old, give it a red background color. In between, orange. A heat map diff of the age of the content, so to speak.

My question is: How I can extract this data from the revisions of a page? Pointers to literature would be equally useful to actual code solving this problem.

Not really relevant, but just in case: It's for a Ruby project, Ruby on Rails in fact. Here's the project, on github.

Update: here's an example test case, written in Ruby. http://pastie.org/631604

Answer 1

One quick way to do it is to get the successive versions of the page and run them through the diff utility to get deltas, so you know what to color how. You could of course reinvent the code that goes from two complete pages and finds which bits they have in common, but it's going to be faster to reuse existing code.

Answer 2

You can use any DVCS to achieve that. I'd recommend git. It will be even better than using db.

Answer 3

One thing. Heat implies activity or energy, so I would flip your colors around so that the most recent are red (hot) and the older text is blue/green (cooled off).

Answer 4

Update: [ long and slightly off-topic answer on longest-common-subsequence deleted ]

I've integrated my Hunt-McIlroy Algorithm subsequence finder with your test case, which now passes. I made various mods to your test case, see it here at pastie.org. Likewise, here is the rdiff module. Here is my svn log for why your test case was changed.