GUIDE: draft format how-to-do-it examples

FORMAT FOR OWL HOW-TO-DO-IT GUIDELINES
First draft, July 21

TITLE
MODELLING PROBLEM
- should include domain-specific example
- should explain why modelling of this feature is not straightforward in OWL
- include criteria required for this pattern to apply
TYPICAL SOLUTION
- modelling approach for the example
- pattern: how to do this in general
HINTS & TIPS
- hints about typical modelling decisions
- links to other patterns
KNOWN USES & REFERENCES
- links to applications that use this
- links to relevant literature


TITLE  Bi-directionality of relations between classes

MODELLIN PROBLEM

OWL properties differ from, for example, UML associations in the sense 
that OWL
properties are directional (from subject to object) and thus models an
association "from one side".

Take for example the following UML association.

[@@ Include fig with association "enrolment" between a student and a
course.]

In OWL, we would need to decide on the direction of the association,
e.g. that the property goes from student to course. Also, adding
cardinality (= multiplicity) constraints can only be done in OWL for
one side of the association:. If the property is defined as student =>
course, you can say how many courses a student may be enrolled in, but
you cannot say how many students may be enrolled in a course.

TYPICAL SOLUTION

If you really need the "bi-directional" view on the association,
you could define two properties, where one is the inverse of the
other:

[@@ include owl language fragments for the example]

So in general, if you have a UML relation which is navigable from both
sides, consider modelling it the following way in OWL:
- Define two properties and define one of them as the "owl:inverseOf"
the other property.
- Choose directional names for the properties, similar to role names
in a UML association
- Attach range and cardinality constraints to the respective
properties.

HINTS & TIPS

- Define the least frequently-used direction as the "inverseOf"
   property.
- @@

KNOWN USES & REFERENCES

@@.

-- 
A. Th. Schreiber, SWI, University of Amsterdam,
Home page: http://www.swi.psy.uva.nl/usr/Schreiber/home.html

Received on Sunday, 21 July 2002 06:48:58 UTC