- From: Dan Brickley <danbri@w3.org>
- Date: Tue, 9 May 2000 20:02:09 -0400 (EDT)
- To: Ravi K Maduposu <ravi@littlebaywebworks.com>
- cc: www-rdf-interest@w3.org
Hi Ravi, On Tue, 9 May 2000, Ravi K Maduposu wrote: > Can any one tell me how to embedd RDF in to Oracle databace and store the > entire structure of RDF and also i am looking for a search engine which is > compatible with RDF format. I'm not sure if this is quite what you're after, but Sergey Melnik has gathered together a summary page describing strategies people have adopted for storing RDF data in RDBMS/SQL systems. Storing RDF in a relational database http://www-db.stanford.edu/~melnik/rdf/db.html A few comments in passing on this issue: the basic approach adopted by many has been to find a rather generic RDBMS schema that can accomdate arbitrary RDF data structures, and to augment this with indexing/caching etc heuristics to improve perfomance (eg. create special-case data structures for commonly encountered properties, eg. Dublin Core attributes). This problem, of storing unpredictable, heterogeneous Web data in (relatively static, table-oriented) RDBMS systems isn't peculiar to RDF. I recently came across this book : Data on the Web : From Relations to Semistructured Data and XML Serge Abiteboul, Peter Buneman, Jim Gray I can't find the Web home page for it, but did find a hyperlink to Amazon's listing: http://www.amazon.com/exec/obidos/ASIN/155860622X/dansuciuswebpage/103-5213514-5457469 While the book doesn't focus much on RDF, the authors adopt the view that _all_ XML data can be interpreted as RDF-like "edge-labelled graphs". Consequently their discussions about how best to store, query, process such data structures is rather useful for RDF implementors. In particular, they discuss strategies for layering a semi-structured XML graph store (with RDF-like data model) on top of an RDBMS. So, that's an approach that connects RDF with the XML "mainstream". A different angle is to explore RDF's affinity with the logic / Knowledge Representation tradition. As http://www.w3.org/RDF/ and the archives of this list show, there have been a number of groups experimenting with the representation of RDF in logic-oriented systems. For example, there is work underway with SWI-Prolog, and with XSB to provide support for RDF processing in these environments. A classic problem in this tradition has been to glue logic/inference oriented systems to mainstream, high performance relational databases like Oracle. There is consequently a literature and toolset here that pre-dates RDF, but which can be picked up and used in an RDF context. XSB (http://xsb.sourceforge.net/) and SWI-Prolog (http://www.swi.psy.uva.nl/projects/SWI/), to pick a couple of packages I've been looking at, both have modules that can talk to ODBC/SQL database servers. see SWI: http://www.geocities.com/SiliconValley/Bit/1116/PrologSQL.html XSB: http://xsb.sourceforge.net/manual2/index.html I don't mean to suggest here that Prolog is the one true approach to RDF query etc. (cue Dan Connolly to mention Algernon and closed-world assumptions ;-) Rather, these are interesting references to follow up as they show (a) how RDF can connect to existing work in the KR-meets-SQL tradition, (b) how tools in the logic/inference tradition might allow _arbitrary_ existing relationally stored data to be exposed as RDF. So, I think these various references suggest a possible hybrid approach: i) strategies needed for storing arbitrary semi-structured Web data (RDF, XML-interpreted-as-graphs) in traditional RDBMS systems. Experiments by others in this Interest Group and similar work in XML/databases area can help here. ii) strategies needed for mapping existing RDBMS table structures into the RDF data model, ie. expressing declaratively the mapping from RDBMS tables to a Web-oriented model (I've been using XSB to experiment with this approach). ii) gluing both of these together: some data will be stored in RDF-specific systems, other data will live in application-specific SQL tables. We should be able to present a unified RDF view to the Web regardless. Getting this combination working well together is one of the things I think many of us are aiming at... Dan -- mailto:danbri@w3.org
Received on Tuesday, 9 May 2000 20:02:15 UTC