[topicmapmail] Hierarchy PSIs

[Kal Ahmed]

The documentation of the PSIs should probably make it clearer that my
intention is that they should be used only to annotate associations
which do conform to the partial ordering constraint *within the context
of the application* - I don't think that it is possible to generalise to
"global". Of course, one can always use TMCL to impose that constraint
while still accepting data from external sources.

Cheers,

Kal

On Mon, 2003-12-29 at 15:25, Bernard Vatant wrote:
> I'm a bit confused with the current debate about hierarchy as defined - or
> not - by Techquila PSIs
> 
> http://www.techquila.com/psi/hierarchy/#hierarchical-relation-type
> http://www.techquila.com/psi/hierarchy/#subordinate-role-type
> http://www.techquila.com/psi/hierarchy/#superordinate-role-type
> 
> In Sowa's Knowledge Representation p.494, I read:
> "hierarchy : A partial ordering of entities according to some relation."
> Followed by examples like supertype-subtype, whole-part, broader-narrower
> ...
> 
> OTOH, I read Tom speaking about "virtual hierarchies" for display purposes,
> and Omnigator displaying hierarchies on the basis that they are declared as
> such by reference to the above PSIs, without any more requirement about
> formal properties.
> 
> If one sticks to Sowa's definition of a hierarchy as a partial order
> (reflexive, transitive, antisymmetric relation), for example
> "predator-prey" is not a hierarchy, since it's not transitive, and can have
> non-trivial loops (A eats B, B eats C, C eats D, D eats A). But nothing
> prevents from declaring this relation as "hierarchical" by reference to the
> above PSIs, and actually it would be interesting to display "locally" for
> each living species its preys and/or predators using a tree-like structure
> (or lattice more exactly in this case); although the "predator-prey"
> relation does not define globally a formal hierarchy.
> 
> So, seems to me that one should make distinct a "display-as-hierarchical"
> type of association type, which basically is what Techquila's PSIs are
> about, and a "formally-hierarchical" type of association type, the latter
> entailing the formal constraint that the relation is indeed globally a
> partial order, and that a topic map using it has been or can be checked to
> be conformant with the matching constraints by any relevant inference tool.
> 
> Bernard Vatant
> Senior Consultant
> Knowledge Engineering
> Mondeca - www.mondeca.com
> bernard.vatant@mondeca.com
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Bernard Vatant
> Senior Consultant
> Knowledge Engineering
> Mondeca - www.mondeca.com
> bernard.vatant@mondeca.com
> 
> 
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-- 
Kal Ahmed <kal@techquila.com>
techquila