the451 has released a report called "Unstructured Data Management" it divides the sector into 4 fields: document management, search and retrieval, categorization and XML databases and tools. The winners would seem to be Documentum, Verity (or Google), Inxight and amazingly Sleepycat. They do believe that in the future it will be Microsoft, Oracle and IBM.
Inxight's profile from the451 report and the full report is here. Interestingly, the companies to watch are: 80-20 Software, Octave Software, Recommind and Semagix. From what I've read no mention of RDF or the Semantic Web (although they do note people like Semagix).