Re: Proposed Resolution for Issue 42

On Tue, 2011-05-31 at 19:29 +0100, Richard Cyganiak wrote:
> On 31 May 2011, at 19:02, ashok malhotra wrote:
> > We discussed issue 42 on the telcon today but did not resolve it at neither Richard
> > nor Enrico was on the call.
> > 
> > The WG seemed inclined to accept the proposal from Souri:
> > -- maintain data equivalence (allowing converting either way, without loss of info) => this can be done by DM 1) always generating schema triples and 2) skipping generation of triples for NULL values
> 
> I would agree to a proposal that maintains reversibility of the mapping by adding rdfs:domain triples to the properties, and does not generate triples for NULL values.

I think that for the moment, we can agree on the current proposal
without speaking about any concrete solution, which will come later when
we're ready for it. rdfs:domain may be enough for this issue, but we may
want other information as well.

> 
> Best,
> Richard
> 
> 
> > 
> > We also discussed whether we needed to prove that a SPARQL query could be generated on the
> > RDF that was equivalent to a SQL query on the Relational data.  The feeling was that, if there was no
> > loss of information, then there would exist a SPARQL query that was equivalent to the SQL query.
> > Alexandre pointed us to some work he had done on this.  See minutes. http://www.w3.org/2011/05/31-rdb2rdf-minutes.html

The relevant email I sent back in October (it's part of the minutes) is
available at [1]. Note that the Information Preservation concern was
already there, more commonly expressed as a Semantics Preservation
theorem.

Since then, we've got people to agree on what semantics means; and it
seems that people are now getting interesting in Semantics Preservation.
But I'm reluctant about providing the formal and complete proofs in the
specs as it's too difficult. But this will give some interesting papers
to the researchers in our group.

Anyway, I'm really/happily surprised to see how closely the development
of the Direct Mapping specification followed what is written in this
email :-)

Alexandre.

[1] http://www.w3.org/mid/1287693123.21135.419.camel@simplet

> > 
> > Richard, Enrico please reply to this mail and let the WG know if you can live with this proposal.
> > We should close this issue next Tuesday.
> > -- 
> > All the best, Ashok
> > 
> 
> 
>

Received on Tuesday, 31 May 2011 19:28:01 UTC