What is a Geospatial Ontology? (2JO4)
In general an ontology specifies of a vocabulary of concepts predicates together with some indication of their meanings. There is a range of levels of precision with which meaning is specified, but an overall goal is that people often want to share a common understanding of the structure of information among people or software agents. Often there are twin targets to make the meaning clear to people while allowing a degree of "automated" processing. In this case an ontology is used to make explicit the semantics and knowledge contained within efforts such as software applications as well as within enterprises and business modeling of particular domains. (2JDG) (2JO8)
As part of such an effort an ontology can be used to enable reuse of domain knowledge and to make domain assumptions explicit or to separate domain knowledge in a declarative form from the operational knowledge which can be implemented in software. (2JDH) (2JO9)
Geospatial ontologies take as their domain a range of geospatial concepts such as seemingly basic things such as topological ideas of "near", "connected" and "around" or general spatial notions such as "place" or "size" and "volume". These provide summative information about spatial things. Geospatial objects may be abstracted to geometrical concepts like a point or polygon area concepts in order to be understood at different levels of granularity. Thus an area like DC can be presented as a small oval on a national map or a complex area when zoomed up close. It also includes more macro, aggregated and complex concepts like "river", "estuary", "pond" and "lake". Ontologies attempt to distinguish all of these concepts in explicit and precise ways to avoid confusions. (2JO7)
Thus an ontology's vocabulary might want to distinguish something called Y that is near X and say: If X is near Y then X and Y are not connected, and also that if X is near Y then Y is also near X. These can be stated in an ontology as axioms rule out the possibility of interpreting “near” as “connected”. One would also need to distinguish near from far since neither is connected. (2JO6)