Last Call Comment: Class-Topic relationships

Raised by:
Sean Bechhofer
Opened on:
Raised by Michael Panzer [1]:

3. Class-Topic relationships

This issue seems to cause some general problems for using SKOS as a
general tool to model classification systems, since the fundamental
entity in a classification system is not the concept but the class, or,
more precisely, the distinction between classes and their subjects.
There are numerous examples of problems that arise by the difficulty of
expressing in SKOS the interplay between a class and the subjects that
form that class on the basis of at least one common characteristic.

The inability to model other than concept-concept relationships with
SKOS sometimes leads to inconsistencies as subjects/topics are
frequently in the domain or range of common classification

In the DDC, this can manifest itself in classes being connected by both
hierarchical and non-hierarchical relationships if modeled with current

<A> skos:narrower <B> .
<B> skos:related <A> .

This arises because what is expressed here isn't really a relationship
between classes, but between topics and classes:

<A> ddc:narrower <B> .
<Topic_in_B> ddc:related <A> .

This pattern can also lead to circular hierarchical relationships:

<A> ddc:narrower <Topic_in_B> .
<B> ddc:narrower <Topic_in_A> .

At the moment in SKOS, this has to be coded at class level:

<A> skos:narrower <B> .
<B> skos:narrower <A> .

which produces inconsistencies. A possible solution would be to
introduce/define ddc:related (or similar relationships) as a new element
without extending SKOS semantic relationships, even if this would mean
lowering the utility of classification systems in SKOS applications.


Related emails:
  1. ISSUE-183: Last Call Comment: Class-Topic relationships (from on 2008-10-08)
  2. Re: SKOS comment: Last Call Working Draft (from on 2008-10-08)
  3. LC Comments: Classification Schemes (from on 2008-10-09)
  4. Re: LC Comments: Classification Schemes (from on 2008-10-13)
  5. ISSUE-183 draft response (from on 2008-10-17)
  6. ISSUE-183 new draft response (from on 2008-10-22)
  7. meeting record: 2008-11-04 SWD telecon (from on 2008-11-04)
  8. [SKOS] Re: SKOS comment: Last Call Working Draft [ISSUE-183] (from on 2008-11-06)
  9. [SKOS] Re: SKOS comment: Last Call Working Draft [ISSUE-183] (from on 2008-11-04)
  10. [SKOS] Update on Last Call Comments (from on 2008-12-02)

Related notes:

2008-11-10: ACTION: Accept

2008-11-11: CHANGE-TYPE: None

2008-11-11: RESOLUTION: SKOS does not indeed offer by default an exact solution to your problem. Our concern with this issue is that its scope might be limited, considering the general context of KOS practice. We have not identified that kind of situation in our Use Cases and Requirements document [2], even for the (UDC) classification case we had [3]. Further, your problem is quite difficult to get. I assume that "subject/topics", even if they are different from classes, are still of conceptual nature -- they indeed play a structuring role in your KOS. They can therefore be modelled as instances of skos:Concept in their own right. Consequently, you could model all your semantic relations as standard SKOS relations, at the level of topic/subjects, or between classes and subjects/topics, without having to represent them at the class level. And thus avoid the cycles you mention. In the light of the assumed relative rarity of your case and existence of a potential solution for it, we propose to *close* ISSUE-183 [ISSUE-183], making no change to the existing SKOS documents. *We hope that you are able to live with this.*

2008-12-15: Closed with no response from commenter.

2008-12-16: COMMENTER-RESPONSE: None