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This page is a collection of starting points for information on ontologies gathered together for ease of reference for our own ontology-related projects. It is made available as is in case it is of use to anyone else. It does not contain information about conferences, meetings, journals, email groups, and the like. This page stays reasonably general, but since our main concern is with natural language processing, there is a bias.
The explosion of ontologies in the last couple of years also makes any expectation of completeness impossible to fulfill. What should be found here are Upper Ontologies and Generic Ontology components that are the most persuasive currently on offer. There are many many many more, either for limited domains or more shallow in their modelling approach. For further collections, see: the DAML ontology library and SchemaWeb.
(these lists claim utility not exhaustiveness!!!)
|What is an ontology?
The usual definition that is offered in the context of AI and knowledge representation is the following by Tom Gruber:
Cf. T. R. Gruber. A translation approach to portable ontologies. Knowledge Acquisition, 5(2):199-220, 1993. Available on line.
And the W3C take on the matter.
A succinct and far reaching position statement concerning the relationship between traditional philosophical ontology and some modern uses of the term is given in Barry Smith's paper 'Ontology: Philosophical and Computational'.
|What is an ontology for?
|An ontology provides an explicit representation for structuring all the entities and relationships that are to be talked about in some domain. Such organisations are expected to be essential for achieving inter-operability between different kinds of knowledge, as they explicitly define the abstract forms and schemes that all knowledge in that domain will take. They also provide ways of ensure more consistent "modelling styles".
|How do I make one?
There are several ways in which one can motivate the contents of an ontology. The extent to which efforts with differing motivations can converge on a single ontology-organisation and list of contents is still unclear. It is more likely that different motivations will result in different ontologies.
The main kinds of motivation can be listed as: formal-philosophical, logical-semantic and linguistic. These can be mixed to greater or lesser degrees; in particular, almost all motivations offered for ontologies draw on linguistic evidence somewhere that is, they consider how particular linguistic items behave in their reasoning about what belongs in an ontology and where. If an ontology is not explicitly aiming at being a linguistic ontology, it is unclear to what extent this kind of argument is justified. I have written a detailed description of the different kinds of ontology motivations relevant when considering Natural Language Processing which can be downloaded in several formats here. Some different motivations are listed in the tables on the right.
The Protégé team offer an Ontology Development Guide that now probably replaces these others: A simple 1-2-3 to get started offered by Tom Gruber here, and Noy and McGuiness's (2001) "Ontology development 101".
For a much more detailed consideration of ontology construction in general, and for a variety of purposes, see the papers:
A good indication of some of the arguments and steps that can (ought?) be gone through when evaluating and critiquing an ontology using the OntoClean methodology is given in this talk by Chris Welty. An in-progress discussion by the group of Nicola Guarino is here.
A paper reviewing metholodogies for ontology construction by Fernández López can be read here (from the IJCAI99 workshop on ontologies and problem solving methods).
A good brief indication of practical issues within the current ontology
scene is Michael Denny's (2002) Ontology
Building: A Survey of Editing Tools
|Recent publications promoting ontologies
|CACM Special Issue (Feb 2002)
|A slide-show by Richard Fikes
|Pease, A., (2001),
of Intelligent Systems: The High Performance Knowledge Bases and IEEE Standard
Upper Ontology Projects, invited position paper, in Proceedings of the
2001 workshop on Measuring Performance and Intelligence Of Intelligent Systems
of a Panel discussion at: KR-2002 : Are upper level ontologies worth the
effort? with Nicola Guarino, Brandon Bennett, Jim Hendler, and Alan Rector.(Download
or requires Explorer)
Towards the Semantic Web: Ontology-driven Knowledge Management. Edited by John Davies, Dieter Fensel & Frank van Harmelen (to appear, Dec 2002)
The following claims
to be the "first semantic web site":Mindswap,
website generated from RDF+ontologies
|Pease, A., Niles, I., (2002) IEEE Standard Upper Ontology: A Progress Report, Knowledge Engineering Review, Special Issue on Ontologies and Agents, Vol 17.
|Some "reference" ontology attempts
Note: some of the ontologies below can also be inspected from the OntoMap portal. To do this, you must register as a user, but this is free. Documentation for the OntoMap portal can be downloaded here.The OntoWeb portal is also very attractive and contains a substantial quantity of ongoing development.
The beginnings of a graphical view can be found here.
|(D)ARPA Knowledge Sharing Initiative
|ANSI Ad Hoc Group: "The most recent meeting of the Ad Hoc Group on Ontology Standards  adopted the upper level ontology resulting from merging content from Cyc, Pangloss, WordNet, and Penman. This draft reference ontology is now available for inspection in several formats, as well as on the web from Cycorp and the KSL Ontolingua Server." (KIF, Cyc)
|DARPA High Performance Knowledge Bases (HPKB) initiative. This overview article appeared in the AI magazine. 1998, Vol. 19, No. 4, pp.25-49. The initiative ended 1997.
|EuroWordNet Online (online access currently appears limited to Spanish, Catalan and Basque) Further development and access will be pursued in the MEANING project
|GermaNet: a WordNet in the spirit of EuroWordNet for German.
|The SUMO (Suggested Upper Merged Ontology) of the SUO working group. Online search DAML version. Teknowlege have also made a graph of the entire thing and give an architecture paper here. I have also put an extract showing the module structure here. But the most uptodate information is on Adam Pease's ontology page here.
|SENSUS, a 70,000-node terminology taxonomy, as a framework into which additional knowledge can be placed. SENSUS is an extension and reorganization of WordNet (built at Princeton University by George Miller, Christiane Fellbaum, and colleagues); at the top level, we have added nodes from the Penman Upper Model, and the major branches of WordNet have been rearranged to fit. (some is browseable here)
|OpenCyc: the free extract of the Cyc ontology, represented in CycL. This includes the upper parts of Cyc's conception of a "human consensus reality". The top portion of the hierarchy is also available here in DAML form.
|GUM: Generalized Upper Model, a grammatically motivated linguistic upper ontology used for interfacing with NLP components.
|BFO (Basic Formal Ontology): latest development from Barry Smith and colleagues.
|FrameNet: an attempt to build up a frame hierarchy, where the frames are essentially motivated by lexicographic concerns and corpus instances.
"126 underspecified semantic types, the 317 systematic polysemous classes
they correspond to and all 39,937 noun instances for each class as derived
from WordNet 1.5"
|Common Comparison/Combination Tasks
|Ontology development appears to go in cycles whereby at irregularly reoccuring intervals there are attempts to merge or combine what has been achieved so far. This list contains some of the most significant or interesting of these efforts, loosely chronologically...
|Upper Cyc and EuroWordNet: Atanas Kiryakov, Kiril Iv.Simov (2000)
|Penman Upper Model represented in Conceptual Graphs (1995)
to WordNet... (WN-verbs->SUMO
adverbs->SUMO, Rev 1.11 and 1.12, 2002).
Mappings for WN2.0 have now also been added and are available at http://cvs.sourceforge.net/viewcvs.py/sigmakee/KBs/WordNetMappings/.
|SUMO to FrameNet... in progress; paper reporting on this work to be presented at FOIS2006.
|Wordnet (extracts) in RDF form (now also in OWL)
|SDTS (Spatial Data Transfer Standard) to Wordnet: Rodrìguez (2000) 'Assessing semantic similarity among spatial entity classes' PhD University of Maine.
(OCT) to WordNetTOP...
English Verb Class Alternations (EVCA)
Multi-Source Ontology is an attempt to combine most available
ontologies into a single knowledge base: well worth a look!
|The current attempt of the ONTAC working group to combine OpenCyc, SUMO and DOLCE (->wiki)
|Some other extensive lists, not all of them up to date or using links that are up to date unfortunately