- From: Marcelo Arenas <marcelo.arenas1@gmail.com>
- Date: Tue, 20 Jul 2010 10:56:51 -0400
- To: Harry Halpin <hhalpin@w3.org>
- Cc: public-rdb2rdf-wg@w3.org
On Mon, Jul 19, 2010 at 10:42 AM, Harry Halpin <hhalpin@w3.org> wrote: >> On Sun, Jul 18, 2010 at 11:39 AM, Harry Halpin <hhalpin@w3.org> wrote: >>> In our specification, it will be important to both specify exactly what >>> needs to be implemented that users can expect to be portable and have >>> extensibility mechanisms that work in a principled manner. >>> >>> The options that we've seen so far both seem to have problems. SPARQL >>> constructs are not expressive enough, but then RIF is likely too >>> expressive, and it would be doubtful if we could convince implementers >>> to >>> implement all of RIF just to map relational data to RDF. Likewise, SQL >>> is >>> a large language itself that is implemented differently in the details >>> across vendors, so we'd have to specify exactly what part of SQL we >>> thought must be implemented. How to do so? >>> >>> I'm intrigued that we could use another option - specify a common >>> semantics using Datalog that then could be expressed using some subset >>> of >>> RIF and SQL. In fact, ideally the language could use Datalog to >>> translate >>> between the subset of RIF and SQL and vice-versa. Then we could also >>> take >>> advantage of SQL's power and implementation exprience while having the >>> nice extensibility mechanisms of RIF. >> >> I like this approach! >> >> The fragment of Datalog that we need to use for the mapping language >> has a simple syntax and a semantics that can be easily understood, so >> it is a good alternative. > > Glad you like it. > > Can you send a few good references about this fragment to the list? Either > papers (ideal) or even references from journal/textbooks? For those of us > who are not familiar with this work, we need something more detailed than > examples in order to figure out the exact fragment that we could map to > RIF. The fragment that I have been mentioning is non-recursive Datalog with equality and safe negation. There is a book just published that shows how this language and its extensions have been used in data integration: Michael Genesereth. Data Integration: The Relational Logic Approach. Morgan & Claypool Publishers, 2010. This short book is available electronically in many libraries. There is also a survey about logic programming that has information about Datalog: Evgeny Dantsin, Thomas Eiter, Georg Gottlob, Andrei Voronkov. Complexity and expressive power of logic programming. ACM Comput. Surv. 33(3):374-425, 2001. I will think about other possible references. All the best, Marcelo
Received on Tuesday, 20 July 2010 14:57:25 UTC