Package schema:

The GUFF core is written in Java (green).
The database file dbdef.xml contains general information (such as database name, path, prefix, table list). For each table, a file xml contains table, fields, indexes and other stuff).
The XML files must be well-formed and valid respect their document type definition (dbdef.dtd and tbdef.dtd).
You can get documentation simply generating HTML files through XSL transformations.