Re: Proposal for the Direct Mapping

Eric,

On Fri, Jul 29, 2011 at 5:21 PM, Eric Prud'hommeaux <eric@w3.org> wrote:

> * Juan Sequeda <juanfederico@gmail.com> [2011-07-29 07:40-0500]
> > Eric, Alexandre,
> >
> > Do you agree with this proposal?
>
> I have to speak with Ivan and Thomas before committing resources to
> re-writing the DM.


I don't think we have to re-write. It's actually just moving things around
and adding new (missing) information.


> Most W3C specs of this complexity have a normative
> formal representation to eliminate ambiguity and to provide a formal
> model as a basis for future work.


I would definitely think that R2RML is much more complex than the Direct
Mapping. It has to be much more complex.


> RDF is on the simple side; its
> formal representation is small enough to be trivial (though always
> written in papers as something like
>  G = { ( (URI×BNode) URI (URI×BNode×Literal)
>          | URI∩BNode=ø, Node∩Literal=ø, Literal∩URI=ø) }
> ) while SPARQL has a pretty complex formalism with graph patterns et
> solutions which is used a lot in advancing the state of the art of
> e.g. rewriting to SQL or conjunction optimization. There's some cost
> to eliminating a normative formalism.
>

The issue is that we have two formalisms, and we can't have both, otherwise
Richard will formally object.

Looking forward to Ivan and Thomas' response.


>
> > Juan Sequeda
> > +1-575-SEQ-UEDA
> > www.juansequeda.com
> >
> >
> > On Tue, Jul 26, 2011 at 3:35 PM, Marcelo Arenas
> > <marcelo.arenas1@gmail.com>wrote:
> >
> > > I agree.
> > >
> > > Cheers,
> > >
> > > Marcelo
> > >
> > > On Tue, Jul 26, 2011 at 3:35 PM, ashok malhotra
> > > <ashok.malhotra@oracle.com> wrote:
> > > > Eric, Marcelo, Alexandre:
> > > > Are you agreeable to this proposal:  Normative text in English.
> > > > Denotational Semantics and Rules as non-normative appendices.
> > > > All the best, Ashok
> > > > On 7/26/2011 11:46 AM, Juan Sequeda wrote:
> > > >
> > > > Richard,
> > > > This is pretty scary... I was working on something exactly the same
> right
> > > > now!!!
> > > > I've read the R2RML spec several times and I really like the way it
> is
> > > done
> > > > (I have some comments, but that will go later), specially the way how
> > > > everything is defined in plain english. So I was going to propose to
> have
> > > > the english as the normative and move the formalism to appendix. This
> way
> > > we
> > > > can all be happy. Anyways, you beat me to the proposal :P
> > > > anyways...
> > > > +1
> > > >
> > > > Juan Sequeda
> > > > +1-575-SEQ-UEDA
> > > > www.juansequeda.com
> > > >
> > > >
> > > > On Tue, Jul 26, 2011 at 1:41 PM, Richard Cyganiak <
> richard@cyganiak.de>
> > > > wrote:
> > > >>
> > > >> Hi all,
> > > >>
> > > >> The Direct Mapping document is stuck because we have a stalemate
> between
> > > >> the editors. With Last Call approaching, we need *some* way of
> breaking
> > > the
> > > >> stalemate. So here's a proposal. This is a possible new outline for
> the
> > > >> document, along with assignments of separate sections to separate
> > > editors.
> > > >>
> > > >>
> > > >>    1. Introduction
> > > >>       - What is this?
> > > >>       - How does it relate to R2RML
> > > >>       - Target audience, assumed level of knowledge
> > > >>       - RDF terms and SQL/relational terms are used as defined in
> > > >>         documents XXX and YYY
> > > >>
> > > >>    2. Example (Informative)
> > > >>       - A simple two-table example
> > > >>       - Quick explanation of foreign key handling
> > > >>       - Quick explanation of tables w/o PKs
> > > >>
> > > >>    3. The Direct Mapping [in Plain English]
> > > >>       - “The Direct Graph of a database is the union of the Table
> Graphs
> > > >>          of all tables in the database.”
> > > >>       - “The Table Graph of a table is the union of the Row
> Graphs...”
> > > >>       - “The Row Graph of a row is ...”
> > > >>       - ...
> > > >>
> > > >>    A. Appendix: Formalisms (Informative)
> > > >>       - should be crisp, short, precise, with only minimum
> explanation
> > > >>         and examples
> > > >>       A.1 Datalog Rules
> > > >>       A.2 Denotational Semantics
> > > >>       A.3 Set-Style Direct Mapping
> > > >>
> > > >>    B. Acknowledgements (Informative)
> > > >>
> > > >>    C. References
> > > >>
> > > >>
> > > >> I see Juan and Marcelo editing A.1.
> > > >>
> > > >> I see Alexandre editing A.2.
> > > >>
> > > >> I see Eric editing 2 (which he already wrote), 3 (which *mostly*
> > > exists),
> > > >> and A.3.
> > > >>
> > > >> I don't know about 1, B, and C.
> > > >>
> > > >> My reasoning is that there is no objective way of picking any of the
> > > >> formalisms over another formalism, so the normative expression
> should be
> > > the
> > > >> lowest common denominator: plain English. By making the formalisms
> all
> > > >> informative, we free them from the burden of having to explain the
> > > direct
> > > >> mapping itself in a generally accessible way. The focus can be
> totally
> > > on
> > > >> presenting the formalisms in all their terseness to an audience that
> is
> > > >> familiar with datalog/denotational semantics/whatever.
> > > >>
> > > >> I hope this proposal aids discussion.
> > > >>
> > > >> Best,
> > > >> Richard
> > > >
> > > >
> > >
>
> --
> -ericP
>