[topicmapmail] role and phenomenon, was TAO vs. ERA

[Jan Algermissen]

[can't post to topicmaps-comment, so I reply here, sorry]

Bernard Vatant wrote:

> But it remains a certain number of cases where role and type are very difficult
> to sort out. 

There is a very good explanation of the difference between role and type in the
great book "Knowledge Representation" by Sowa ( http://users.bestweb.net/~sowa/krbook/ ).

The chapter is called "Phenomenon, Role and Sign" (p. 80) and here is a quote:

"An entity's appearance independent of context is sufficient to classify it
by a phenomenal type, but context is essential for classifying it by role. The
type Nail, for example, is a phenomenal type - long and thin with a point at
one end. A common use of a nail is to fasten things made of wood; in that
context a nail would be a fastener. But fastener is a role type that could be
applied to many things of many different phenomenal types: Nail, Tape, Hook,
Button String or PaperClip"

I am delighted how well topic maps support the distinction between
role and phenomenon and that they seem to force us to be aware of
that distinction all the time!

Jan