Objectives

Add support for Virtuoso as a data server. (We may want to keep alive the support to present technologies)

Virtuoso, some details

Virtuoso is a data server providing several features for managing and serving various kind of data/information.
It has a open source version, which lacks some key features (namely Database virtualization and Data Replication), but it still offers a large amount of useful ones.

It manages RDF, XML, has a DB and manages files/contents (through WebDAV)
It implements RDBM functionalities, and accept ODBC/JDBC APIs (among others), it also offer Object-Relational database features (SQL-2000)
It can present data (from DB, also legacy ones) as XML using XMLType, in any case it is an XML storage accepting XPath, XSLT, XQuery and SQLX.
It offers standard SPARQL protocol to access RDF data, which are stored internally (apparently converted in some DB structure, transparently).

These features would replace the present sesame storage and the filesystem storage. Of course it's possible to use just some of the features and keep using the "old" method for others (e.g. we may choose to keep storing files on the filesystem - even though we'd miss WebDAV features, and centralization of resources).

The application works as a web service, accessing it is a matter of HTTP/*DBC calls, so the integration with other software shouldn't require the use of new languages and the like (it also offer its own development language for writing web applications, but we can skip it).

It is a very large project serving various purposes, and it will need, on our part, a thorough study of all its features before using it.[

Replacing existing technologies

The idea is to use Virtuoso as an XML repository and as an RDF storage. Possibly as a content storage too.
Virtuoso offers drivers for Sesame (and others), using Virtuoso's store and SPARQL implementation as a back end for Sesame. Virtuoso will do all the query and implementation while Sesame offers the interface.
AFAIU this will make it easier to use it, as we'll still access Sesame. Then, behind the scene, Virtuoso comes in. It may saves us some troubles (But this must be checked!)

Dealing naturally with XML (and accepting several languages for querying it), it seems sensible to use it for this purpose.

As for content storage, the key point can be centralization of the data, and WebDAV functionalities

Short term

It seems a bit too optimistic to say that we start using Virtuoso in the short term. First of all because, being it a large product and offering several features, we will need to study them all and it will take a while.
Then, since we're discussing about replacing existing solutions, we'll need to change our code (Talia) extensively to start using it.
Nonetheless it may offer several advantages above current solutions, and it keeps evolving, possibly offering further (and better) features in the future.

Versions

As said, there is a open source version of it, which lacks some features. Then there is the commercial version which has a quite high price tag.
We'll probably take the open source version into consideration, but if the commercial version features are needed in the future, it can always be bought at later time.

While I can't see into the future, since they have this open source version now, it should be safe to assume they will keep it open for a while. Doing otherwise may hurt their public image, and credibility. Though, I haven't read any statement on this front...