As they say, a picture speaks a thousand words, so I am exposing two views of Virtuoso that have been on the Web for while.

Remember, Virtuoso offers data management, data access, web application server, enterprise service bus, and virtualization of disparate and heterogeneous data sources, as part of a single, multi threaded, cross-platform server solution; hence it's description as a "Universal Server".

Conceptual View:

Technical View (kinda missing PHP, Perl, Python runtime hosting in the Virtual Application Sever realm):

Virtuoso's architecture is not a reaction to current trends. The diagrams above are pretty old (with minor touch ups in recent times). At OpenLink Software, we've have a consistent world-view re. standards and the vital role they play when it comes to developing software that enables the construction and exploitation of "Context Lenses" that tap into a substrate of Virtualized Logical Data Sources (SQL, XML, RDF, Web Services, Full Text etc.).