Innovation and Ontologies

180 Classification – The OntoCube
figure 61 Spectrum of ontologies by Lassila & McGuinness (2001)
The categories and their meanings are (Lassila & McGuinness, 2001; McGuinness, 2002):
• Controlled vocabulary: a finite list of terms. Catalogs are an example of this category, providing
unambiguous interpretation of terms.
• Glossary: a list of terms with their meanings specified as natural language statements. This
provides more information since humans can read the natural language statements. Typically
interpretations are not unambiguous and thus not adequate for computer agents.
• Thesaurus: provision of some additional semantics between terms. Giving information such as
synonym relationships, they do not supply an explicit hierarchy. In many cases, relationships
may be interpreted unambiguously by agents.
• Informal is-a hierarchy: i.e. hierarchy taken from specifications of term hierarchy (e.g. YAHOO).
This is not a strict subclass or is-a hierarchy, but rather represents subordinate components.
• Formal is-a hierarchy: including strict subclass relationships. If A is a superclass of B, then if an
object is a subclass of B, it is necessarily a subclass of A as well. Strict subclass hierarchies are
necessary to deploy inheritance.
• Formal is-a hierarchy that includes instances.
• Frames: that is, inclusion of classes and their properties which can be inherited by classes of the
lower level.
• Ontology with value restrictions: restrictions might be placed on what can fill a property.
• General logical constraints: making the ontology the most expressive. Ontologists can specify
first-order logic constraints between terms by use of ontology languages.