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Virtuoso

Virtuoso can be used in the case where we need to provide mash-ups/services using data available from several data sources. The plan is: extract data from data sources (using APIs provided), triplify them and linking them to the Web of data in such a way that added value is generated. In this case, Virtuso is used as the RDF native storage to store all triples, and for setting up the SPARQL endpoint provided. On the other hand, "D2R": http://www4.wiwiss.fu-berlin.de/bizer/d2r-server/ is an excellent tool to triplify your own dataset and build your own SPARQL endpoint.

The Open Source Edition doesn't include the Virtual Database Engine and Data Replication Functionality of the Commercial Edition.
Virtual database in the simplest form provides the ability to search across several databases with a single query. Virtuoso extends this query functionality and data transformation through hosted logic, SQL, SQL stored procedures and XML, and the Virtuoso PL.

A bit complicated to use!

Service

Following installation, users and passwords in Virtuoso can be managed using the command line tools (see the full documentation) or via the Conductor web application which is installed by default at http://localhost:8890/conductor. Two users ("dba" and "dav") are created by default, with administrative access to Virtuoso. Secure passwords must be chosen for these users in order to complete the installation. If you leave this blank, the daemon will be disabled unless a non-default password already exists.

IPSYP Virtuoso server:

Scalability

http://www.openlinksw.com/weblog/oerling/?id=1487

RDF from RDBMS

Virtuoso offers a wizard for dynamically generating & publishing RDF based Linked Data from ODBC or JDBC accessible relational data sources.

Entity Search, Find, and Explore

http://192.168.10.22:8890/fct/

Publications - Technical Reports

  1. Mapping Relational Data to RDF with Virtuoso's RDF Views
    Abstract. Among its many talents, OpenLink Virtuoso Universal Server includes SPARQL support and an RDF data store tightly integrated with its relational storage engine. This article provides an overview of how to use Virtuoso to dynamically convert relational data into RDF and expose it from a Virtuoso-hosted SPARQL endpoint.
  2. Mapping Relational Data to RDF in Virtuoso
    Abstract. This paper discusses Virtuoso's new declarative Meta Schema Language for mapping SQL Data to RDF Ontologies. This functionality, commonly referred to as "RDF VIEWs", enables the exposure of pre-existing ODBC or JDBC accessible relational data as Virtual RDF Graphs thereby exposing said data to SPARQL query access directly or via Virtuoso's in-built support for SPARQL within SQL (SPASQL). The entire process results in RDF Data sets and optimized data access without physical regeneration of RDF Data Sets from SQL Data.
  3. Virtuoso - SPARQL and Scalable Inference on Demand
    Abstract. This paper discusses integrating inference capabilities into OpenLink Virtuosos SPARQL implementation. Our goal is to do inference at run time and on demand wheneverpossible, instead of materializing entailed facts ahead of demand. In an open web scenario,facts are liable to change, to be retracted, to be contradictory and to be malicious. Therefore,heavy investment in materializing consequences for a very large body of likely questionable facts is in our view not advisable. In the same spirit, we support partial query evaluation, so as to return possibly incomplete results within a fixed response time window. We present Virtuoso’s run time implementation of owl:sameAs, inferred identity based on inverse functional properties, generic SPARQL extensions for arbitrary transitive subqueries and partial query evaluation. As future work, we suggest ways of generalizing these features for support of arbitrary backward and forward chaining rules.