Re: Proposal for the Direct Mapping

* 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. 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. 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.

> 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

Received on Friday, 29 July 2011 22:21:51 UTC