(unknown charset) Re: Broader, collections and the difference between SKOS and OWL

Greetings... all ... I am new to this list, although I have been following 
SKOS development for a longer time.

Simon:  You bring up a critical issue, and I'm really pleased to see 
attention to this point.

Two observations I'd like to share:

1. Section 2.3.1 of the SKOS Primer is (in my opinion) problematic for the 
very reasons Simon points in his email.

The notion of '"dirtier" hierarchies' conflicts of the meaning of the 
concept of "hierarchy", and does *not* follow thesaural and taxonomic 
standards.

The KOS/vocabulary community has very strict rules for hierarchy and the 
BT/NT hierarchical relationships must pass the test of "true" inheritance 
within the scope of the domain (or world) being represented.

Vocabulary creators need to describe the world they are representing.

Allowing for "dirtier" hierarchies will create a mess and interfere with 
the potential for interoperability among SKOS schemes in general or 
with any OWL schemes.

Basically a concept/class "is" or "is not" a hierarchy.  If something is 
to be classed as a dirty hierarchy, it really ought to be considered an 
"associative relationship".  It seems to me efforts need to be directed to 
considering specific types of associations...e.g. process/product, 
activity/agent, and so forth, an area I'd be pleased share more about if 
anyone is interested.

2. I don't believe it matters if you/we/anyone uses the word 
class/concept/term, although they are not "equivalent" in the sense of a 
true thesauri ;)  wink!

A term represents a concept, and it can be referred to as a class in an 
abstract sense.

As you all know, we could use the word object or resource too...for the 
"entities" being represented w/SKOS.  What ever "x" is used, it needs to 
be used consistently.

Having shared this observation, I would discourage the use of the word 
"subject term" or "subject heading" for two reasons.  First, SKOS can be 
used for named entities that may be used to represent (1.) embodied 
thought (simply descriptive cataloging)--physical/observable and measurable 
aspects of an object, and (2.) expressed thought (simply 
intellectual/subject analysis).  Second, subject headings, as you know, 
are ugly yet very creative beasts dealing with syntagmatic structuring. 
Subject headings are not suited for SKOS in the raw, although a SKOS 
scheme could help build subject headings following a protocol.

thanks for reading and letting me chime in.

peace! jane




On Fri, 15 Feb 2008, Simon Spero wrote:

> [I'm currently working on a more formal model, but I wanted to post an 
> outline to get some feedback (and to keep me away from LaTeX related 
> avoidance behavior :) .
>
> The key point is that SKOS Concepts do not correspond directly to 
> concepts/classes but instead more closely resemble Subject Terms.  If 
> this distinction is taken into  account, and the relationship between 
> the SKOS Concept and its associated class is explicitly modeled, many 
> outstanding issues with SKOS become much easier to resolve cleanly.
>
> ]
>
> 1: Svenonius on Subject Terms.
>
> Subject language terms differ referentially from words used in ordinary 
> language. The former do not refer to objects in the real world or 
> concepts in a mentalistic world but to subjects. As a name of a subject, 
> the term Butterflies refers not to actual butterflies but rather to 
> the set of all indexed documents about butterflies. (Svenonius 2000, p. 
> 130)
>
> 2: SKOS Concepts are Svenonian Subject Terms, not concepts.
>
> 3: The extension of a SKOS Concept is the set of all documents which 
> have that SKOS Concept as a subject; compare with the definition of an 
> rdfs class in RDF Semantics (Hayes 2004)
>
> 4: Concept schemes are defined in the context of a specific domain 
> (which may be general).  Relationships need not be valid outside that 
> domain (Turbine/Fan/Blades ISO; Parrots BT Pets in a pet shop 
> thesaurus).
>
> 5: Relationships between SKOS Concepts are relationships between Subject 
> Terms, not Classes.   These relationships entail a different set of 
> relationships between the  Classes associated with those Subject Terms.
>
> 6: Every hierarchical relationships between Subject Terms in Controlled 
> Vocabularies must be transitive by definition. The relationships they 
> entail between underly classes need not be.  Transitivity across 
> different subtypes of hierarchical relationships is only valid at the 
> level of their least common subsumer.
>
> [ A hierarchical relationship] is assigned to a pair of terms when the 
> scope of one of the terms totally includes (is broader than) the scope 
> of the other. (Dextre Clarke 2001, p. 42)
>
> There seems to be no particular logical reason why the part-whole 
> relationship should not be generally applicable. It only has to meet the 
> test of always being true, just as with the other hierarchical 
> relationships. (Milstead 2001, p.60)
>
> This test of total inclusion is a rigid property of hierarchical 
> relationships.   Given that associative relationships are defined 
> negatively as relationships which are neither hierarchical nor 
> equivalence, and  that the standards specify that relationships that are 
> not truely broader are associative, an intransitive skos:broader cannot 
> be disjoint with skos:related.
>
> 7:   A  skos:broader B  means: every document  ( within the domain of 
> the concept scheme) about A must also be about B.    Thus:
>
> Wheels BT Cars   == Every document   about wheels is also a document 
> about cars.
> Cars BT Vehicles == Every document about cars is also a document about 
> vehicles.
> |----------------------------------------------------------------------------------------------------------------
> Wheels BT Vehicles == Every document about wheels is also a document 
> about vehicles
>
> It is incorrect to infer any relationship between the class of Wheels 
> and the class of Vehicles given only a plain broader/BT assertion
>
> 8:   A BTG B means:  every document about A must also be about B because 
> the class of As is a subclass of the class of Bs.
>
> Cars BTG Vehicles == Every document about cars is also about vehicles, 
> because a car is-a vehicle.
> Convertibles BTG Cars == Every document about convertibles is also about 
> cars, because  a convertible is a car
> |----------------------------------------------------------------------------------------------------------------------------------------------------
> Convertibles BTG Vehicles == Every document about convertibles is also 
> about vehicles, because a convertible is a vehicle
>
> 9: A BTP B means:  every document about A must also be about B, because 
> every A is in some sense part of a B.
>
> Fingers BTP Hands == Every document about fingers  is also about Hands, 
> because every finger is part of a hand.
> Hands BTP People == Every document about hands  is also about People, 
> because every hand is  part of a person.
> |----------------------------------------------------------------------------------------------------------------------------------------------------
> Fingers BTP People == Every document about fingers is also about People, 
> because every finger is part of a person.
>
> 10:  The exact relationship between the classes of two SKOS Concepts 
> that are BTP depends on the nature of  partitive relationship.  Some 
> subtypes of BTP may allow a more precise transitive semantics for the 
> related Classes.
>
> 11:   A BTI B means:  every document about the individual A is also 
> about B, because A is an instance of  B.    BTI is subset of BTG;  thus 
> transitivity is maintained for the underlying classes
>
> My S2000 BTI Convertibles == Every document about my S2000 is also about 
> Convertibles, because my S2000 is-a convertible
> Convertibles BTG Cars == Every document about convertibles is also about 
> cars, because  a convertible is-a car
> |----------------------------------------------------------------------------------------------------------------------------------------------------
> My S2000 BTI Cars == Every document about my S2000 is also about cars, 
> because my S2000 is-a car
>
> 12: SKOS Collections correspond to arrays, and to what Svenonius termed 
> "perspective hierarchies".    These types of hierarchies are useful for 
> representing classificatory structures; it might be possible to infer 
> quasi-facets , or specific properties.
>
> More to come
>
> Simon
>
>
> References
> Hayes, Patrick (2004). RDF Semantics. Recommendation. World Wide Web 
> Consortium.
> URL: http://www.w3.org/TR/2004/REC-rdf-mt-20040210/
>
> Milstead, Jessica L. (2001). “Standards for Relationships between Sub 
> ject Indexing Terms”. In: Relationships in the Organization of 
> Knowledge. Ed. by Carol A Bean and Rebecca Green. Information science 
> and knowledge management. Dordrecht: Kluwer Academic Publishers. Pp. 
> 53–66. ISBN: 0792368134.
>
> Svenonius, Elaine (2000). The Intellectual Foundation of Information 
> Organization. Cambridge, Mass.: MIT Press. ISBN: 0262194333 (hc : alk. 
> paper).
> URL: http://www.netlibrary.com/AccessProduct.aspx?ProductId=39954.
>