Fwd: comments on the BLD proposal

Chris,

On Tue, Sep 23, 2008 at 10:22 AM, Chris Welty <cawelty@gmail.com> wrote:

> Alexandre,
>
> Thank you for taking the time to provide us with comments. Some responses
> below.
>
> Alexandre Riazanov wrote:
>
>
Some irrelevant stuff skipped...


>
>
> > (3) Use case 4.2 in http://www.w3.org/TR/2008/WD-rif-ucr-20080730/ uses
> > frames as (individual-valued) base terms.
> > The BLD spec does not seem to provide either syntax or semantics for such
> > use. Does it mean that such use was
> > considered initially but didn't make it to the spec?
>
> The syntax and semantics do specify individual-valued frames, one of their
> most obvious uses on the semantic web is for RDF triples. What leads you to
> believe that the syntax or semantics are not provided? Or perhaps you mean
> something different by "(individual-valued) base terms".
>
> e.g. the RDF triple
>
> <http://ex.com/john> <http://ex.com/uncleOf> <http://ex.com/mary>.
>
> can be written in the frame syntax as
>
> <http://ex.com/john>[<http://ex.com/uncleOf> -> <http://ex.com/mary>]
>
> where <xxx> is a shortcut for xxx^^rif:iri.
>

The triple above is obviously a statement which can
only have a boolean value. The frame can also be interpreted
as a statement (equivalent to the triple), but it can
also be used in a place where a resource-valued term is
expected, e.g. it can be the filler in a property:

<http://ex.com/paul>
   [
      <http://ex.com/father> ->
           <http://ex.com/john>
               [<http://ex.com/uncleOf> -> <http://ex.com/mary>]
   ]

In this case, the value computed by the frame is just <http://ex.com/john>,
which is not boolean. The slots can be considered as qualifiers
of <http://ex.com/john> and have to be treated semantically as,
for example, additional constraints on <http://ex.com/john>.
This is, of course, syntactic sugar.

Nether syntax, nor semantics of BLD covers such use, and I am actually
fine with this in principle. The only problem is that the use case 4.2
has "?buyer[card -> ?creditCard deliveryAddr -> ?address]" as the second
argument of the (positional) predicate "provide", and also
"?date[month -> ?month year -> ?year]" as a filler for "expiry",
and several other examples like this.

> (4) In general, it would be extremely helpful (to me as an implementer) to
> see a reference translation to FOL.
> IMHO, the standard would be the right place for it.

By "reference translation to FOL" do you mean to take a set of BLD Formulae
> and translate them to FOL sentences? Or a logical embedding of the semantics
> of BLD in FOL?
>

The latter. As an implementor, I would prefer the semantics
written as a translation to FOL to the model-theoretic semantics (this one
is good too, but for other purposes).



> (5) Minor thing: isn't External(c) a well-formed (base) term when c is a
> constant?

No, See Section 2.2, Item 8. External is meant to be an anchor for an
> external function call, so External(c) is not a term, but External(c()) is.
>

Then it overrides clause 7 in 2.4 in the FLD spec, that
says "If t is a constant, .. then External(t) is an *externally defined term
*."


Cheers,
======================================
Dr. Alexandre Riazanov (Alexander Ryazanov)
Montreal, Canada
cell: +1 - 514 - 961 86 89
http://www.freewebs.com/riazanov/
http://www.linkedin.com/in/riazanov
======================================



-- 
======================================
Dr. Alexandre Riazanov (Alexander Ryazanov)
Montreal, Canada
cell: +1 - 514 - 961 86 89
http://www.freewebs.com/riazanov/
http://www.linkedin.com/in/riazanov
======================================