- From: Juan Sequeda <juanfederico@gmail.com>
- Date: Sun, 18 Jul 2010 11:26:50 -0500
- To: Harry Halpin <hhalpin@w3.org>
- Cc: public-rdb2rdf-wg@w3.org
- Message-ID: <AANLkTin0R7jEiSomj-SMdw5ozXpKEuzHzQxRzooJanML@mail.gmail.com>
Harry On Sun, Jul 18, 2010 at 10:39 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. > Yes!! +1 > > However, I'd like to know exactly what part of RIF-BLD covers Datalog, and > what exact fragment of SQL maps to Datalog. Examples of mappings are not > enough, we'd have to specify the kinds of RIF/SQL expressions that would > be allowed and how both expressions mapped to Datalog. > I think the datalog to RIF question is for Harold Boley. In [1] it states: SPARQL can be partially mapped to Datalog (and thus to the RIF-Core subset of RIF-BLD) Does that mean that it is all of RIF-BLD? Maybe we should has Harold Boley. And about datalog to SQL, if I'm not wrong (marcelo and dan, please correct me) the correspondence are just SELECT-FROM-WHERE without aggregation and grouping... basically the core relational algebra (selection and projection). If i'm not wrong, then that means that this corresponds to Horn clauses without recursion and negation. [1] http://www.w3.org/TR/rif-bld/ > cheers, > harry > > > >
Received on Sunday, 18 July 2010 16:27:23 UTC