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Re: RDB2RDF Working Group

From: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
Date: Mon, 23 Nov 2009 18:01:30 +0000
Message-ID: <492f2b0b0911231001p64d0e82axe6e54e7de198e3a4@mail.gmail.com>
To: Axel Polleres <axel.polleres@deri.org>, marcelo.arenas1@gmail.com
Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
I am not sure that the following is of any relevance, but I thought I
mention it anyway ;-)
To some extend OWL has the power to express key constraints etc. For
example, you can say that each Person must have exactly one social
security number:
SubClassOf(Person ObjectExcactCardinality(1 hasSSN owl:Thing))
or in clause form:
Person(x) and hasSSN(x, y1) and hasSSN(x, y2) -> y1=y2
Person(x) -> hasSSN(x, f(x)) for f(x) some skolem constant.
The limiting factor in OWL versus RDBs is more that OWL can (natively
without reification) only express binary relations whereas DBs work
over n-ary relations. This might render OWL's abilities not suitable
for what you want.
Anyway, I think it is an interesting topic and I hope I can keep a bit
up todate about what the RDB2RDF group is doing.

2009/11/23 Axel Polleres <axel.polleres@deri.org>:
> FYI, some conversation with Marcelo Arenas from the RDB2RDF working group which I share with his permission...
> Axel
> Begin forwarded message:
>> From: Axel Polleres <axel.polleres@deri.org>
>> Date: 23 November 2009 15:40:50 GMT+01:00
>> To: "Marcelo Arenas" <marcelo.arenas1@gmail.com>
>> Subject: Re: RDB2RDF Working Group
>> Hi Marcelo!
>> Good to hear from you!
>> First of all, can I share this conversation with the SPARQL WG/Chairs?
>> (I ask because you addressed to me alone)
>> Now my answer:
>> Looking forward to collaborate with you on the RDB2RDF side of the liaison with SPARQL...
>> Indeed the definition of integrity constraints such as keys and foreign keys is not a part of SPARQL.
>> In fact, SPARQL is not a data definition language: we define a query language (SPARQL/query [1]) and
>> a data manipulation language (SPARQL/update [2]), but aren't chartered for designing data definitions...
>> Dataset descriptions, as far as we are concerned with (as a part of SPARQL/service descriptions [3])
>> will be very basic, just providing hooks to data descriptions at most, that is a minimal set of properties to link to dataset descriptions in some external formalism (concretely void and saddle have been discussed earlier,
>> but we will most likely not actively promote a particular data definition language).
>> I hope that clarifies matters. in fact, I'd honestly see the definition/description of constraints on datasets as something on the side of extensions of OWL/RDF Schema rather than on the side of SPARQL. That latter sentence is my personal view... probably something to be discussed/suggested in the upcoming "next steps on RDF" W3C workshop.
>> best regards,
>> Axel
>> 1. http://www.w3.org/TR/sparql11-query/
>> 2. http://www.w3.org/TR/sparql11-update/
>> 3. http://www.w3.org/TR/sparql11-service-description/
>> On 23 Nov 2009, at 15:29, Marcelo Arenas wrote:
>>> Dear Axel,
>>> As you probably know, there is a new working group in the W3C whose
>>> mission is to standardize a language for mapping relational data into
>>> RDF and OWL  (RDB2RDF WG). I am an invited expert in that group.
>>> The work on SPARQL is fundamental for the work of the RDB2RDF WG, so
>>> we would like to coordinate our efforts with that of the SPARQL WG.
>>> For that reason, I have volunteered to be the liaison between the
>>> RDB2RDF group and your group.
>>> Currently, we are trying to define the list of features of the data
>>> definition language of SQL that will be supported in the mapping
>>> language for relational data into RDF and OWL. One of these features
>>> is the definition of integrity constraints such as keys and foreign
>>> keys, so I was wondering whether you have discussed about the
>>> possibility of including integrity constraints in the data definition
>>> language of SPARQL. I took a look at the SPARQL WG Wiki and I couldn't
>>> find any reference about this, but maybe I am missing something. Thank
>>> you in advance for any information about this.
>>> Cheers,
>>> Marcelo

Dr. Birte Glimm, Room 306
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+44 (0)1865 283529
Received on Monday, 23 November 2009 18:02:00 UTC

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