Tuesday, February 14, 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]
Sub-theme
n-articulated
ontological framework
[168] [169] [170] [171] [172] [173] [174]
Communication to the Protégé forum from Dirk
Andrea said:
>UML has no attached DL, and it has no precise specification at all
of the
>meaning of its elements. It is only intended to defines a graphical
>notation and nothing more. Actually, UML has 9 kinds of diagrams.
UML certainly has higher aspirations than just being a graphical notation. For one, it certainly wants to be a fully executable language one day and people are working on it.
There is no reason to leave a major language specified unambiguously deliberately. It just takes time, like any large specification effort.
>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
I think you got it backwards. Despite its heritage in programming languages, UML was designed to be expressive, hence the large number of different modeling techniques it offers.
OWL and the like have been designed with computability issues in mind (rather than giving the modeler what he needs). The whole extrinsic vs intrinsic definition of classes discussion shows that nicely. If you want an inferencing engine, you need a set-theory like approach. Since UML users typically don't need that, they have not constrained by this.
On the specific issue of an object being an instance of multiple classes: I think direct instance-of is overused, massively. What is missing is more use of a concept like is-role-of, and that would do away with these frequently incomprehensibly deep class hierarchies.
Dirk