WAL files format

Hi,

iam developing version control system based on content because i havent
found anything for postgres and it sounds like great tool to have.
Propably i will use Rules and Views with shadow tables, but iam
interested in alternative to examine WAL files.

So iam interested in WAL file format and information that can be
extracted from it. Is there any way to build some API above WAL file to
be able to analyze data changes in time caused by DML ? Iam aware of
xlog.c but not of its capabilities and features, its kind of hard for me
to analyze that file.

MS SQL create transaction logs and there are tools like ApexSQL Log that
can analyze logs a redo changes made by DML. So i thought it would by
great to have such tools for opensource system like postgres.

Also, if anybody has any ideas or alternatives on content version
control system i will be realy thankfull.

Thanks Milos