How to create a versioning/history/revision system for contents published by users?

Question

After reading a lot of SO questions about Keeping page changes history or How to version control a record in a database (for example), I can't find a real elegant solution to do the work.

Now, let's try to explain as clear as possible what we need, for this simple revision system, that allows registered users to post some articles, and other users to submit a revision of those articles, and then some moderators users to check those revisions.

MySQL database

The database contains an articles table with the following simplified fields:

ARTICLE(id, id_user, title, content, date);

To implement the revision/history versions, I guess that we'll have the following table:

REVISION(id, id_article, revision_id_user, id_moderator, revision_date, 
         revision_title, revision_content, revision_description, revision_check);

With the relation : ARTICLE 0,n <---> 1,1 REVISION

Workflow

• A user create an ARTICLE, which is inserted in the ARTICLE table (terrific !)

• Another user makes an update of this ARTICLE, this update is recorded in the REVISION table, and is queued for the moderator users. (revision_check=0).

• A moderator user validate the REVISION(revision_check=1), then the ARTICLE(content) gets the REVISION(revision_content) value.

My questions

• Is this workflow seems to be a good way to do it? Because, I see a mistake: if there are several REVISIONs for an ARTICLE:

• Should we take the content of the last submitted REVISION or the original ARTICLE?
• Or, should we need to block the revisions as no other REVISION could be submitted while the last isn't checked.

• Is there a way to record light versioning? By the way, is it possible to insert in the REVISION table, only the updated content through a SQL, PHP or js compare function? And how to display it like SO do it? Because I'm afraid that the REVISION table will be very heavy.

• Bonus : how does SO?

Any idea, link, source, plugin (MySQL, PHP 5 and JS/jQuery) would be greatly appreciated.