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

Yay! This is what Dan and I have been saying from the beginning (datalog ->
sql, datalog -> rif). Seems like we haven't been eloquent enough. But glad
that we are all on the same page!


Juan Sequeda
+1-575-SEQ-UEDA
www.juansequeda.com


On Mon, Jul 19, 2010 at 9:42 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.
>
> If I can get these references or this information out of the meeting
> tomorrow, I'm happy to try to get Harold Boley, Michael Kifer to work out
> the semantics of mapping that fragment to RIF, and we'd probably need to
> have a discussion with Sandro (W3C RIF contact) on introducing RIF to this
> WG (as I would assume that most of us aren't familiar with it).
>
> The other topic would be to see if this SQL fragment would be a good
> starting point for the SQL-based approach as well.
>
> >
> > 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:
> >
> >
> http://www.w3.org/2001/sw/rdb2rdf/wiki/Database-Instance-Only_and_Database-Instances-and-Schema_Mapping
> >
> > All the best,
> >
> > Marcelo
> >
> >
>
>
>