Dear All, (01)
ISO 15926 has strengths and weaknesses which are different to those
of OWL (any variant). I have attempted to illustrate these on the
attached slides. (02)
slide 1: This shows the ISO 15926 approach to defining the class "dog
owner". The diagram is intuitive because the class definition in the
grey area is similar to the instance diagram below. Unfortunately,
ISO 15926 fails to define formally the class "dog owner" even where
cardinalities are specified for the (class of ) relationship "owner
of dog". This is because the ISO 15926 makes the true statement that
every "dog owner" owns a dog, but cannot say that everybody who owns
a dog is a "dog owner". (03)
slide 2: This shows the ISO 15926 approach to a common class of
engineering problem. The grey part of the diagram shows that a seam
of type X contains two "occurrences" of a rivet of type Y. Within the
grey part of the diagram all the cardinalities are 1-to-1. The grey
part of the diagram is isomorphic to the instance diagram below -
this is important because it makes it easy to understand.
Unfortunately as with slide 1, ISO 15926 makes some true statements,
but does not provide formal definitions. (04)
However, in slide 2, ISO 15926 gets far closer than any other
approach to providing something useful to engineers. The approach of
slide 2 can be extended to an engineering assembly of any complexity
without loosing intelligibility, because it is isomorphic to the
instance diagram. I do not think that the intelligibility can be
retained using OWL. (05)
NOTE 1: I have used the term "occurrence" in the way that it is used
within ISO 10303. This is an important concept in engineering, but
those working in ontologies have not addressed it. (06)
NOTE 2: The isomorphism between the relationships between classes in
a design and between individuals in a realization of a design allows
ISO 10303 to contain models that are vague about whether an instance
of an EXPRESS entity represents a class or an individual. In a more
formal approach, we cannot have the vagueness, but equally we do not
want to loose the intuition provided by the isomorphism. (07)
Best regards,
David (08)
============================================================
David Leal
CAESAR Systems Limited
registered office: 29 Somertrees Avenue, Lee, London SE12 0BS
registered in England no. 2422371
tel: +44 (0)20 8857 1095
mob: +44 (0)77 0702 6926
e-mail: david.leal@xxxxxxxxxxxxxxxxxxx
web site: http://www.caesarsystems.co.uk
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the_iso_15926_approach.pptx
Description: Binary data
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