Rinke Hoekstra

The BestMap ontology adds an extensional perspective to SKOS relations, which allows the specification of many-to-many mappings between SKOS vocabularies. It is represented using some of the new OWL 2 constructs, such as role chains and disjoint properties.

You can download the latest version of BestMap from:

http://www.best-project.nl/owl/bestmap.owl

This ontology is made available under the Creative Commons Attribution 3.0 Netherlands Licence.

Extensionality

One of the main drawbacks of the existing mapping relations in SKOS is that they allow only one-to-one mappings between SKOS concepts. The BestMap approach is based on the idea that there is an underlying assumption of extensionality in the semantics of SKOS. That is, the meaning of concepts is not just determined by the skos:semanticRelations individual skos:Concept instances may have, but also by the kinds of resources that may be annotated using these concepts.

Example

For example, given a skos:broader relation between :Frog and :Amphibious_Animal, and the annotation of a Wikipedia article on frogs using :Frog, we can readily assume that article is about :Amphibious_Animal as well. The same holds for the mapping relations of SKOS: skos:narrowMatch, skos:broadMatch etc.

It is this annotation perspective – this extensionality – that BestMap captures by extending the existing SKOS mapping relations in role chains with two `annotation’ object properties: bm:about and bm:describes. The former is used to relate a resource to a concept, and the latter for the inverse. Because of OWL 2 DL’s global restrictions on the (re)use of properties in role chains, it further introduces bm:d_about and bm:d_describes to be able to specify a direct relation between the resource and a skos:Concept. All BestMap properties are respectively defined as rdfs:subPropertyOf the bm:about and bm:describes properties.

Example

BestMap specifies the role chain bm:d_about o skos:broader-> bm:b_about (any bm:d_about relation, followed by a skos:broader relation is a subproperty of bm:b_about). Given the skos:broader relation between a :Frog and :Amphibious_Animal, a bm:d_about relation between :Frog and the Wikipedia article, an OWL2 compliant reasoner can infer a bm:b_about (and therefore a bm:about) relation between :Amphibious_Animal and the Wikipedia article.

This is functionality that the standard intensional semantics of SKOS relations does not provide. See below for an overview of the available relations in the BestMap ontology (the bm:describes relations are defined in an analogous fashion)

Mapping

Specifying a mapping between two (or more) vocabularies now becomes a straightforward exercise in defining the proper OWL2 class axioms (value restrictions) on the properties provided by BestMap: a mapping is an OWL class that is defined to be equivalent or subsumed by these class axioms (all BestMap mappings are a subclass of bm:Mapping). A resource with (appropriate) annotations a SKOS vocabulary using the BestMap properties, can then be inferred to be an instance of the mapping class, and be assigned new relations with any other SKOS concepts used in the value restrictions.

Example

For the BEST project, we needed to specify many-to-many mappings between a layman vocabulary, containing commonsense concepts, and a legal vocabulary, containing terms related to unlawful acts. This allows us to infer `legal annotations’ for descriptions of cases in layman terms. An illustrative example is the case of a woman who was kicked by a horse at a riding school. Given the mapping class:

and appropriate skos:broader relations between the horse, the riding school, the kicking, and respectively lv:animal, lv:company and lv:dangerous_action. An OWL reasoner will determine our case to be of type ex:AO_Mapping (because of the equivalence with the conjunction of the value restrictions on bm:about), and it will furthermore infer bm:d_about relations with tv:animal, tv:animal_owner and tv:damage.

The way this works is shown in the picture below (dotted lines are inferred relations).

OWLED 2009 Presentation

Relevant Publications