Sunday, February 12, 2006
Generative Methodology Glass Bead Games
n-articulated ontological framework
On using RDF to model web services
Link back to part of the “solution” to translations between
RDF / OWL and Models of Information -> [167]
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n-articulated
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Paul, Rebecca and all,
UML has no attached DL, and it has no precise specification at all of the meaning of its elements. It is only intended to define a graphical notation and nothing more. Actually, UML has 9 kinds of diagrams that are intended to model both the static aspects and the dynamic behavior of a system, but I suppose you guys refer to class diagrams for static modeling only here.
Anyway, can one can give semantics to an UML (class) diagram? This is a point of strong criticism. To understand why, consider that UML allows to draw objects which are instances of a class, but it does not tell, for example, whether an object can be an instance of multiple classes and/or can change the class(es) it is an instance of over time.
In set theory: "can an element be included in more than one set?” Can an element belong to different sets in different time instants?
This is often considered to obviously hold in the Knowledge Representation community where "class" means "set", but it is not so in the context of object-oriented programming, where for efficiency reasons it is assumed that objects are instances of a single class and that the class they are instance of never changes until the object is destroyed (ok, with exceptions, say Smalltalk).
So, UML is pretty good for documenting software design, where many contextual assumptions are implicitly made, but personally I would not rely on UML if I were to define an unambiguous standard specification.
Best regards,
Andrea