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AW: Databases on the Semantic Web

From: Alexander Maedche <maedche@fzi.de>
Date: Wed, 13 Mar 2002 08:30:49 +0100
Message-ID: <BC630F6C39BFAB4CA1B35EFA0C7F217F0A48B2@stan.fzi.de>
To: <Joachim.Peer@unisg.ch>, <www-rdf-interest@w3.org>

We developed a tool called REVERSE that allows
extracting RDF statements from a relational database
according to a predefined ontology.

It is open-source and online available at:


In its current status it provides only a static
mapping from the tuples in the relational database
to RDF. We are working on a dynamic transformation.


-----Ursprüngliche Nachricht-----
Von: Joachim.Peer@unisg.ch [mailto:Joachim.Peer@unisg.ch] 
Gesendet: Montag, 11. März 2002 09:53
An: www-rdf-interest@w3.org
Betreff: Databases on the Semantic Web

hi All,

I have a question about the exposure of databases to the Semantic Web. Basically, I would like to know your opinion: What do you think, will semantic annotations (encoded in RDF) be used to

(a) expose only the (semantics of a) database schema (and provide a description how to access it)

or will it be used to

(b) expose (the semantics of) both database schemata and *database data* ?

Which variant is more reasonable?

Here my opinion:

Variant (a) will need some description format like DAML-S to describe the means to access the databases. Variant (a) has the advantage that access control etc. may be handled more elegantly than in (b). However, reasoning over such a database will by very hard, because you first have to fire the "right" query to get the "right" data (which then might be asserted to the knowledge base of the agent). At least to me, it seems that inference between several databases can by very hard (impossible??) this way.

Variant (b) has the advantage that an agent(logical reasoner) could _directly_ access and reason about _all_ data, thus enabling inference between _multiple_ databases. However, it has the disadvantage that one has to dump that whole database to RDF periodically.

What do you think?
Can't wait to hear your findings and opinions!


PS: I have read the article on exposure of database to the Semantic Web[1] and I experimented with the implementation in [2] - does anyone have additional ressources on that topic?

[1] Tim Berners-Lee. "Relational Databases on the Semantic Web" http://www.w3.org/DesignIssues/RDB-RDF.html

[2] DbView.py - "view an SQL DB thru RDF glasses", Open Source implementation by Dan Connolly http://www.w3.org/2000/10/swap/dbork/dbview.py

Joachim Peer
Research Assistant
Institute for Media and Communications Management Blumenbergplatz 9 CH-9000 St. Gallen
Tel.: ++41 (0)71 224 3441
Received on Wednesday, 13 March 2002 02:30:51 UTC

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