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Coments on 1st Working Draft

From: Martin Bryan <mtbryan@sgml.u-net.com>
Date: Thu, 8 Aug 2002 09:04:10 +0100
Message-ID: <0ebb01c23eb5$d6b00de0$1cc466c3@yourudvgq1w43i>
To: <public-webont-comments@w3.org>

Congratulations on a superb first working draft for the OWL specifications.
This is the clearest explanation of how to markup ontologies I have seen to

As ever with first drafts, there are a few rough edges that need smoothing,
as noted below.

Abstract Syntax
Section 2 states that "elements that can occur any number of times
(including zero) are enclosed in braces". Yet in most cases where braces are
used in the spec the presumption is that at least one occurence is required.
For example unionOf (<description> {<description>}) would seem illogical if
the text comment in parenthesis was taken into account. Is
unionOf(<description>) really allowed?

Section 3.
At present <authorship-etc> is only allowed to be specified at ontology
level. This assumes that all entries in the ontology are created/validated
at the same time by the same person. In practice ontologies are created by
teams, different members of which are responsible for different entries. The
spec contains no mechanism for indicating the responsibility for specific
entries, the time of their creation or the period in which they can be
considered valid. No mechanism is identified for annotating entries, e.g. by
use of the XML schemas annotation element. Some standardized mechanism for
identifying fact and axiom managment information is required.

The fact that class/datatype IDs can be the same as property or individual
IDs goes against the principles of the use of the term ID within XML. Under
what circumstances is it invisaged that a class would have the same name as
an individual, or a property the same name as a datatype?

The OWL Lite restrictions on minCardinality and maxCardinality given in the
formal productions state that only (1) may be used, yet section 3,4 of the
Feature Synopsis for OWL Lite and OWL clearly states that 0 is permitted for
both these productions.

The formal production for ObjectProperty is defined in such a way that an
object cannot be both Functional and Transitive. Yet the text of the
preceding paragraph ends "Finally, individual-valued properties can be
specified as transitive" with no qualification about the use of this term
with respect to functionality.

2, Class Elements
What would happen if an imported enumeration element failed to match a local
one. (It seems that there is no way to override or extend imported
definitions: unless there is an exact match there is an error. This seems to
be a major failing, as typically users will want to restrict or extend
imported definitions.)

2, Property Elements
The equivalentTo element is listed without any namespace qualifier. (OK so
its deprecated, but is should still have its origin clearly specified.)

2, Instances
The first example confusingly shows two items with the same rdf:ID. Is this
allowed? If so, is it good practice?

Feature Synopsis of OWL Lite and OWL

No mention is made in this otherwise excellent introduction of how to apply
multlingual names to a fact. The only mechanisms that seem to be provided
are the sameClassAs and sameIndividualAs ones. A neater way of identifying
different linguistic terms for a concept are needed. (There seems to be no
way of assigning human readable names to facts, or to axioms. Apparently
they can only be assigned identifiers, which will often be meaningless.)

Martin Bryan

The SGML Centre, 29 Oldbury Orchard, Churchdown, Glos GL3 2PU, UK
Phone/Fax: +44 1452 714029  E-mail: mtbryan@sgml.u-net.com

For further details about The SGML Centre visit http://www.sgml.u-net.com
Received on Thursday, 8 August 2002 04:30:31 UTC

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