What I've seen with OMG-promulgated standards is that the people involved know what they are doing but (1) they do a bad job communicating it, (2) people do a bad job of understanding it, (3) as with the W3C compromise in the standards process leads the specification to miss the last 20% that you need to make something that really works, and (4) some adopters of the standard see filling that last 20% as what differentiates them from competitors, so the standard is not so standard.

There are many homologies between W3C and OMG standards, one of them is that there is a mapping between the semantics of documents and the semantics of API calls, object definitions, etc. linking all the way back to the CORBA standards. Another is between the XSLT/XPath functions and the "Object Constraint Language". The OMG and W3C maintain a largely overlapping list of primitive data types, for instance.

Neo4J and similar products tend to support the "property graph" model which can be modeled with RDF/SPARQL.

As for document databases, that gets to the magic about RDF which is most obscure: a document full of facts is an RDF "graph". You can take the union of all of the facts in two documents and that is also a graph. You can take the union of all the facts in two million graphs and run SPARQL queries on it without doing any data transformation or import!

This is a necessary condition for a "universal solvent" for combining data from multiple sources but RDF standards haven't been sufficient. Serious semwebbers know about techniques like "smushing" that go a long way towards finishing the job, but oddly these are not incorporated into standards or widely known among beginners.