The main object of MCDB meta-information is so-called article. It is the document which describes a set of MC event files, generation parameters, applied cuts, used physical models, etc.

Shema itself is located on MCDB main server http://mcdb.cern.ch/hepml/schemas/0.1/mcdb-article.xsd
This schema extends sample-description.xsd from the main LCG HepML schema with additional MCDB-specific information.

Full schema structure and reference is available here

Logical schema structure

Graphical structure view