Help:Ontology

Ontologies are used to capture knowledge about some domain of interest. An ontology describes the concepts in the domain and also the relationships that hold between those concepts.

• Components of Ontologies
  • IDIVIDUALS: represent objects in the domain in which we are interested.
  • PROPERTIES: are binary relations on individuals - i.e. properties link two individuals together. For example, the property "Has historical geographical allegiances" might link the tune "Craig a' Bhodich" to the tune "Fisher's Hornpipe", or the property "Is also known as" might link the tune "Fisher's Hornpipe" to the tune "Crannciuil Ui Fishuir". Properties can have inverses. For example, the inverse of hasOwner is isOwnedBy. Properties can be limited to having a single value, i.e. to being functional. They can also be either transitive or symmetric.
  • CLASSES: are interpreted as sets that contain individuals. They are described using formal (mathematical) descriptions that state precisely the requirements for membership of the class. For example, the class Tune would contain all the individuals that are tunes in our domain of interest Classes may be organised into a superclass-subclass hierarchy, which is also known as a taxonomy. Subclasses specialise (`are subsumed by') their superclasses. For example consider the classes Music and Tune, Tune might be a subclass of Music (so Music is the superclass of Tune). This says that, `All Tunes are Music', `All members of the class Tune are members of the class Music', `Being a Tune implies that you're a piece of Music', and `Tune is subsumed by Music'.

Object Property Characteristics
Ontologies allows the meaning of properties to be enriched through the use of property characteristics.

• Functional Properties
  • If a property is functional, for a given individual, there can be at most one individual that is related to the individual via the property. If we say that the individual "A M Shinnie" Was composed by "Angus Fitchet" and we also say that the individual "A M Shinnie" Was composed by "James Scott Skinner", then because Was composed by is a functional property, we can infer that "Angus Fitchet" and "James Scott Skinner" must be the same individual. It should be noted however, that if "Angus Fitchet" and "James Scott Skinner" were explicitly stated to be two different individuals then the above statements would lead to an inconsistency.

• Inverse Functional Properties
  • If a property is inverse functional then it means that the inverse property is functional. For a given individual, there can be at most one individual related to that individual via the property. This is the inverse property of Was composed by since Was composed by is functional, Is the composer of is inverse functional. If we state that "Angus Fitchet" is the Composer of "A M Shinnie", and we also state that "James Scott Skinner" is the birth composer of "A M Shinnie", then we can infer that "Angus Fitchet" and "James Scott Skinner" are the same individual.

• Transitive Properties
  • If a property (P) is transitive, and the property relates individual (a) to individual (b), and also individual (b) to individual (c), then we can infer that individual (a) is related to individual (c) via property (P). For example, if the individual "Jackey Layton" -> Is also known as-> "Jack Lattin", and "Jack Lattin" -> Is also known as -> "Jennie Rock the Craddle", then we can infer that "Jackey Layton" -> Is also known as -> "Jennie Rock the Craddle".