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Fwd: comments on the BLD proposal

From: Alexandre Riazanov <alexandre.riazanov@gmail.com>
Date: Wed, 24 Sep 2008 13:47:00 -0400
Message-ID: <a7f786b70809241047l4a64823i8076862bbb2f4117@mail.gmail.com>
To: public-rif-comments@w3.org

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/father> ->
               [<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

Dr. Alexandre Riazanov (Alexander Ryazanov)
Montreal, Canada
cell: +1 - 514 - 961 86 89

Dr. Alexandre Riazanov (Alexander Ryazanov)
Montreal, Canada
cell: +1 - 514 - 961 86 89
Received on Wednesday, 24 September 2008 17:59:57 GMT

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