Re: Using Datalog as a common semantics for SQL/RIF-based approaches?

On Sun, Jul 18, 2010 at 11:39 AM, Harry Halpin <> 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.

We have been working with Juan in the mapping language and also in a
comparison with Eric's default mapping, that we would like to present
to the group tomorrow. Hopefully tonight you will be able to find this
material here:

All the best,


Received on Monday, 19 July 2010 13:15:31 UTC