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Comments on RDF Concepts and Abstract Data Model

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Sun, 27 Oct 2002 10:53:45 -0500 (EST)
Message-Id: <20021027.105345.01427650.pfps@research.bell-labs.com>
To: www-rdf-comments@w3.org

		Comments on RDF Concepts and Abstract Data Model


Vital comments:

What is the point of the ``social meaning'' stuff?  Is it supposed to
indicate that RDF documents available on the web are not always
supposed to be considered to be assertions?  If so, how is this done?
Can I, for example, use rdfs:comment to put disclaimers into an RDF
document?  If there is no way in RDF to make such disclaimers, then
why bother to bring up the possibility? 

I find the whole example about clowns to be completely mystifying.  If
you take this example at face value, then *any* use of any RDF commits
to the natural language implications of rdfs:comment tags.  How can
any organization deploy an RDF-aware application under these
circumstances (except by having that application understand the
implications of arbitrary natural language).

Similarly, the tying of the meaning of a URI to the ill-specified
intent of some organization poses a giant bar to the deployment of
RDF.  Under these circumstances how can any organization use an URI
that they do not own?  The owning organization might, after all,
choose to change the meaning of any URI they own at any time.  This
seems to me to be a bar to any communication between organizations
using RDF.


Major comment:

The RDF graph is syntax.  As such it makes no sense to define a notion
of equality over literals, which are pieces of syntax.  It is just as
if one wanted to defined equality in C by defining it over pieces of a
C program.  Similarly, it makes no sense to define equality of nodes
or triples.


Minor comments:

Model theory is a mathematical term, not something that is only used
and understood by logicians.  As model theory has a consistent meaning
throughout the RDF documents, there is no reason to qualify the term.

It would be much better if the examples in the document made sense.
For example, floats(oil,water) is not a triple that makes sense,
unless you make oil denote some particular bit of oil that is
currently floating on some particular bit of water, which does not
appear to be the intended meaning of these terms in the example.
Similar problems are exhibited by the boiling example.

RDF does provide and, in some sense, requires some inferential
machinery.  In particular RDFS requires that rdfs:subClassOf be
transitive.

The definition of datatypes is incompatible with XML Schema.  Removing
the requirement that each value have a lexicalization would remove a
source of incompatability, and would not change anything as far as RDF
is concerned.
Received on Sunday, 27 October 2002 10:53:53 GMT

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