Where is the Common Data Model (CDM) documented?

The CDM is used in the Toolbox to allow data from different datasets to be processed by the Toolbox tools, workflows and applications. Where can i find more information about the CDM?

The first Common Data Model specification can be accessed through this link :

CDM: Common data model specification - v1.0

Here is a link to the updated, simpler version of the documentation: CDS Toolbox requirements