From: Frank van Harmelen (Frank.van.Harmelen@cs.vu.nl)
Date: 09/25/01
It's good to see so much activity around the topic of query languages and storage devices. Clearly the time is ripe for this. Perhaps the following is unnecessary, but I thought it would be useful to provide a map to this rapidly expanding section of acronym space (it's certainly useful for my own sanity, perhaps it helps others as well). Frank. ---- QUERY LANGUAGES - DQL: query-language for DAML+OIL, proposed by Richard Fikes et al in [1] - RQL: query-language for RDF Schema, proposed by the people from Heraklion [2] - RDQL: query-language for RDF, from the folks at HP Labs Bristol [3] Remark 1: By saying that "X is a query language for Y", I mean that both the syntax and the semantics of X provide facilities to deal with modelling primitives from Y. So, in a trivial way, any RDF query language is also an RDF Schema query language, but only in a trivial way. Any propoer RDF Schema query language should support (for instance) querying the subClassOf relation, taking into account its transitivity. Remark 2: Since there are such clear containment relations between the language RDF, RDF Schema, DAML+OIL, I would very much hope that it will turn out to be possible to reflect this stacking of languages in the corresponding query languages. STORAGE DEVICES Besides query languages, there also some new developments for storage devices. - RDF: There are already quite a number of RDF storage devices out there. I will not bother to repeat them, see the RDF resource page at [4] - RDF Schema: I am aware of only one storage device that is tailored towards RDF Schema, namely Sesame, at [4] - DAM+OIL: Mike has just recently proposed the first DAML+OIL specific storage device, called DAMLDB, at [6] Remark 3: In general, these storage devices are independent from a particular query language, but of course a storage device for language X will most likely have support for a query language for X. Eg: Sesame stores RDF Schema, and supports RQL, but support for DQL could well be built on top of the same storage device. Frank. --- [1] DQL proposal: http://www.daml.org/listarchive/joint-committee/0572.html [2] RQL tutorial: http://sesame.aidministrator.nl/doc/rql-babysteps.html [3] RDQL home page: http://www-uk.hpl.hp.com/people/afs/RDQL/ [4] RDF storage tools: http://www.ilrt.bris.ac.uk/discovery/rdf/resources/ [5] Sesame home page: http://sesame.aidministrator.nl [6] DAMLDB page: http://www.daml.org/2001/09/damldb/
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