Re: Suggestion for SKOS FAQ

On Fri, Mar 7, 2008 at 4:54 PM, Andreas Langegger <al@jku.at> wrote:

>
>  thanks for the pointer to issue-44. I didn't read deep into the thread.
> But as Antoine pointed out, there is the transitive version also (obviously
> the result of the issue-44 discussion). So both kinds of semantics can be
> expressed in the model and are not defined by the application.
>

The problem with the introduction of an intransitive "broader" relationship
is that such a relationship is fundamentally incompatible with the Broader
Term relationship as defined in ISO-2788 et. al.

The defining characteristic of hierarchical relationships  is that they are
totally inclusive.  This property absolutely requires transitivity.  If this
condition does not apply, the relationship is associative, not hierarchical.
  Renaming the broader and narrower term relationships doesn't change this;
all it has done is cause confusion.

As an example of the confusion so caused, note that associative
relationships remain disjoint from broaderTransitive (S24)?    If "broader"
can be intransitive, this constraint is inexplicable.

Let A,B,C be Concepts,
       A broader B,
       B broader C,

and suppose that transitivity does not hold (  NOT A broader C)

By S18,  we have
      A broaderTransitive B,
      B broaderTransitive C,
By S21,
      A broaderTransitive C

and hence, by S24,
      NOT A related B,
      NOT B related C,
      NOT A related C

We have NOT A broader C and NOT A related C, so there can't be any
relationship between A and C  at all!

Simon