Re: Relationship between EricP's default mapping and Datalog rules approach?

On Sun, Jul 18, 2010 at 1:38 PM, Juan Sequeda <> wrote:
> On Sun, Jul 18, 2010 at 12:23 PM, Harry Halpin <> wrote:
>> > Harry,
>> >
>> > On Sun, Jul 18, 2010 at 8:26 AM, Harry Halpin <> wrote:
>> >
>> >> While I enjoyed the talk last week, I was wondering about the
>> >> relationship
>> >> between Eric's proposed direct mapping [1] and the rules put forward
>> >> last
>> >> week by Marcelo [2]. This question goes to both, and the entire working
>> >> group.
>> >>
>> >> One of the advantages of Eric's default mapping mechanism [1] is that
>> >> it
>> >> allows relational data to be expressed in RDF without the author of the
>> >> mapping knowing *any* rules or having any ontology that he or she wants
>> >> to
>> >> map their relational data to.
>> >>
>> >
>> > This is exactly the same as the Database-Instance-Only mapping.
>> Are we sure? Eric - thoughts?
>> There's at least two differences I see. Syntactically, ericP is not
>> generating any new predicate URIs (foaf:name), thus his insistence on
>> creating a "stem graph" with default URIs. I imagine this will just be a
>> simple option, with the generateURIs being created by a call to some
>> standardized interface to the Linked Data Web via a search engine like
>> Sindice, a vocabulary management service, or something like OKKAM.
> I think this is an issue of the syntax. A predicate needs to be created.
> This is the semantics. How it's going to be done is another issue.
>> The second difference is how Eric decided to express his semantics, i.e.
>> using sets rather than Datalog-ish rules that resemble FOL. I went over
>> Eric's work only once, but I believe we need to make a decision as a
>> Working Group to pick one style of doing semantics and stick with it in
>> the spec, even though they are technically equivalent, i.e. we should
>> choose between set-theoretic model theory or just a mapping to
>> FOL/Datalog/RIF semantics with a standard interpretation.
> Honestly, I have trouble understanding the semantics that Eric has written.
> I would recommend using Datalog because
> 1) it has well defined semantics
> 2) it can be translated to RIF
> 3) it can be translated to SQL

I fully agree with Juan on this. The fragment of Datalog that we need
to use for the mapping language has a simple syntax and semantics, has
been extensively used in the database community for data integration
and exchange, and it can be easily translated into SQL.

Received on Monday, 19 July 2010 12:44:25 UTC