The Object Management Group has posted the IT Portfolio Management Facility as a final adopted specification. I guess there's still a finalization phase to iron out any remaining issues.
If you're looking for an object model for your CMDB, this is an excellent place to start: directly implementable, yet concise, described in an industry standard syntax (UML). When they get further they will post the XML Metadata Interchange file, which will make it importable into many UML tools (from which class models can be generated).
OMG specs are noted for their depth and rigor, and in my opinion this one sets a high bar for others working in this space to meet - not that it's perfect. If I have time, I'll dig into it in a little more depth.