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Upper ontology (computer science)
From Wikipedia, the free encyclopedia
In information science, an upper ontology (top-level ontology, or foundation ontology) is an attempt to create an ontology which describes very general concepts that are the same across all domains. The aim is to have a large number on ontologies accessible under this upper ontology. It is usually a hierarchy of entities and associated rules (both theorems and regulations) that attempts to describe those general entities that do not belong to a specific problem domain.
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Upper ontologies are commercially valuable, creating competition to define them. Peter Murray-Rust has claimed that this leads to "semantic and ontological warfare due to competing standards", and accordingly any standard foundation ontology is likely to be contested among commercial or political parties, each with their own idea of 'what exists'.
No one upper ontology has yet gained widespread acceptance as a de facto standard. Different organizations are attempting to define standards for specific domains. The 'Process Specification Language' (PSL) created by the National Institute for Standards and Technology (NIST) is one example.
There is debate over whether the concept of using a single, shared upper ontology is practical. These arguments are outlined below.
A well-known and quite comprehensive ontology available today is Cyc, a proprietary system under development since 1985, consisting of a foundation ontology and several domain-specific ontologies (called microtheories). A subset of that ontology has been released for free under the name OpenCyc, and a more or less unabridged version is made available for non-commercial use under the name ResearchCyc.
The BFO or Basic Formal Ontology framework developed by Barry Smith and his associates consists in a series of sub-ontologies at different levels of granularity. The ontologies are divided into two varieties: SNAP (or snapshot) ontologies, comprehending continuant entities such as three-dimensional enduring objects, and SPAN ontologies, comprehending processes conceived as extended through (or as spanning) time. BFO thus incorporates both three-dimensionalist and four-dimensionalist perspectives on reality within a single framework. Interrelations are defined between the two types of ontologies in a way which gives BFO the facility to deal with both static/spatial and dynamic/temporal features of reality. Each SNAP ontology is an inventory of all entities existing at a time. Each SPAN ontology is an inventory (processory) of all the processes unfolding through a given interval of time. Both types of ontology serve as basis for a series of sub-ontologies, each of which can be conceived as a window on a certain portion of reality at a given level of granularity.
Developed by Nicola Guarino and his associates at the Laboratory for Applied Ontology (LOA), the Descriptive Ontology for Linguistic and Cognitive Engineering (DOLCE) is the first module of the WONDERWEB foundational ontologies library. As implied by its acronym, DOLCE has a clear cognitive bias, in that it aims at capturing the ontological categories underlying natural language and human commonsense. DOLCE, however, does not commit to a strictly referentialist metaphysics related to the intrinsic nature of the world. Rather, the categories it introduces are thought of as cognitive artifacts, which are ultimately depending on human perception, cultural imprints and social conventions. In this sense, they intend to be just descriptive (vs prescriptive) notions, that assist in making already formed conceptualizations explicit. DOLCE is an ontology of particulars, in the sense that its domain of discourse is restricted to them. Of course, universals are used to organize and characterize the particulars, but they are not themselves subject to being organized and characterized (e.g., by means of metaproperties). DnS (Descriptions and Situations), developed by Aldo Gangemi (LOA, Rome), is a constructivist ontology that pushes DOLCE’s descriptive stance even further. DnS does not put restrictions on the type of entities and relations that one may want to postulate, either as a domain specification, or as an upper ontology, and it allows for context-sensitive ‘redescriptions’ of the types and relations postulated by other given ontologies (or ‘ground’ vocabularies). The current OWL encoding of DnS assumes DOLCE as a ground top-level vocabulary. DnS and related modules also exploit ‘Codeps’ (Content Ontology Design Patterns), a newly created tool which provides a framework to annotate ‘focused’ fragments of a reference ontology (i.e., the parts of an ontology containing the types and relations that underly ‘expert reasoning’ in given fields or communities). Both DOLCE and DnS are particularly devoted to the treatment of social enties, such as e.g. organizations, collectives, plans, norms, and information objects. The DOLCE-2.1-Lite-Plus version, including a number of DnS-based modules, has been and is being applied to several ontology projects.
The General Formal Ontology (GFO), developed by Heinrich Herre and his colleagues of the research group Onto-Med in Leipzig, is a realistic ontology integrating processes and objects. It attempts to include many aspects of recent philosophy, which is reflected both in its taxonomic tree and its axiomatizations. GFO allows for different axiomatizations of its categories (such as the existence of atomic time-intervals vs. dense time). The basic principles of GFO are published in the Onto-Med Report Nr. 8.
Two GFO specialties, among others, are its account of persistence and its time model. Regarding persistence, the distinction between endurants (objects) and perdurants (processes) is made explicit within GFO by the introduction of a special category, a persistant. A persistent is a special category with the intention that its instances "remain identical" (over time). With respect to time, time intervals are taken as primitive in GFO, and time-points (called "time boundaries") as derived. Moreover, time-points may coincide, which is convenient for modelling instantaneous changes.
WordNet, a freely available database originally designed as a semantic network based on psycholinguistic principles, was expanded by addition of definitions and is now also viewed as a dictionary. It qualifies as an upper ontology by including the most general concepts as well as more specialized concepts, related to each other not only by the subsumption relations, but by other semantic relations as well, such as part-of and cause. However, unlike Cyc, it has not been formally axiomatized so as to make the logical relations between the concepts precise. It has been widely used in Natural Language Processing research.
The Suggested Upper Merged Ontology (SUMO) is another comprehensive ontology project. It includes an upper ontology, created by the IEEE working group P1600.1 (predominantly by Ian Niles and Adam Pease). It is extended with many domain ontologies and a complete set of links to WordNet. It is freely available.
Examples of domain ontologies can be found at the Open Biomedical Ontology site. They act as an umbrella organisation for many ontologies specific to biological topics (such as cellular organelles).