Additional commentary from Orri Erling. re. ORDBMS, ADO.NET vNext, and RDF (in relation to Semantic Web Objects):

More Thoughts on ORDBMS Clients, .NET and RDF:

Continuing on from the previous post... If Microsoft opens the right interfaces for independent developers, we see many exciting possibilities for using ADO .NET 3 with Virtuoso.

Microsoft quite explicitly states that their thrust is to decouple the client side representation of data as .NET objects from the relational schema on the database. This is a worthy goal.

But we can also see other possible applications of the technology when we move away from strictly relational back ends. This can go in two directions: Towards object oriented database and towards making applications for the semantic web.

In the OODBMS direction, we could equate Virtuoso table hierarchies with .NET classes and create a tighter coupling between client and database, going as it were in the other direction from Microsofts intended decoupling. For example, we could do typical OODBMS tricks such as prefetch of objects based on storage clustering. The simplest case of this is like virtual memory, where the request for one byte brings in the whole page or group of pages. The basic idea is that what is created together probably gets used together and if all objects are modeled as subclasses of (subtables) of a common superclass, then, regardless of instance type, what is created together (has consecutive ids) will indeed tend to cluster on the same page. These tricks can deliver good results in very navigational applications like GIS or CAD. But these are rather specialized things and we do not see OODBMS making any great comeback.

But what is more interesting and more topical in the present times is making clients for the RDF world. There, the OWL Ontology Language could be used to make the .NET classes and the DBMS could, when returning URIs serving as subjects of triple include specified predicates on these subjects, enough to allow instantiating .NET instances as 'proxies' of these RDF objects. Of course, only predicates for which the client has a representation are relevant, thus some client-server handshake is needed at the start. What data could be prefetched is like the intersection of a concise bounded description and what the client has classes for. The rest of the mapping would be very simple, with IRIs becoming pointers, multi-valued predicates lists and so on. IRIs for which the RDF type were not known or inferable could be left out or represented as a special class with name-value pairs for its attributes, same with blank nodes.

In this way,.NETs considerable UI capabilities could directly be exploited for visualizing RDF data, only given that the data complied reasonably well with a known ontology.

If an SPARQL query returned a resultset, IRI type columns would be returned as .NET instances and the server would prefetch enough data for filling them in. For a SPARQL CONSTRUCT, a collection object could be returned with the objects materialized inside. If the interfaces allow passing an Entity SQL string, these could possibly be specialized to allow for a SPARQL string instead. LINQ might have to be extended to allow for SPARQL type queries, though.

Many of these questions will be better answerable as we get more details on Microsofts forthcoming ADO .NET release. We hope that sufficient latitude exists for exploring all these interesting avenues of development.