1. Classifications, Taxonomies, Ontologies, Thesauri The following three terms: classifications, taxonomies and ontologies are often confused. This is caused by a trend to use the most fashionable of the three terms “ontology”.

2. Classification: Definition Merriam-Webster definition: systematic arrangement in groups or categories according to established criteria. An example of a classification would be the division of all plants in the classes decorative and non-decorative.

3. Taxonomy: Definition Longman definition: the process or a system of organizing things into different groups that show their natural relationships, especially plants or animals Meriam-Webster definition: orderly classification of plants and animals according to their presumed natural relationships A taxonomy can described as (hierarchical) classification of items created according to data internal criteria.

4. Ontology: Yet Another Definition "The term ontology has many meanings and shades of meaning. In the contest of this work*, we refer to what is sometimes called a "structural" ontology -- a machine readable set of definitions that create a taxonomy of classes and subclasses and relationships between them.“ * Web Ontology (WebONT) Working Group Charter at http://www.w3.org/2001/sw/WebOnt/charter

5. Classifications and Taxonomies: Comparison Taxonomies are classifications that: have hierarchical structure list items that are organised according to their natural relationships

6. Taxonomies and Ontologies Most ontologies could be described as taxonomies + definitions + various properties and relations (rather than just taxonomic, i.e., is_a, relations)

7. Thesauri and Ontologies Nowadays, thesaurus most commenly means a listing of words with similar, related, or opposite meanings. "A formal definition of a thesaurus designed for indexing is: a list of every important term (single-word or multi-word) in a given domain of knowledge; and a set of related terms for each term in the list.“* "In Information Technology, a thesaurus represents a database or list of semantically orthogonal topical search keys. In the field of Artificial Intelligence, a thesaurus may sometimes be referred to as an ontology.“* Additional reading: http://www.metamodel.com/article.php?story=20030115211223271 * http://en.wikipedia.org/wiki/Thesaurus

8. Animal Kingdom Taxonomy Kingdom, class, order, genus, species Gray wolves are dogs. Dogs are carnivore. Carnivores are mammals. Mammals are animals. National Center for Biotechnology Information (US): –http://www.ncbi.nlm.nih.gov/Taxonomy/

9. Ontology Management and Maintenance Tools Protégé is a free, open source ontology editor and knowledge-base framework. Protégé ontologies can be exported into a variety of formats including RDF(S), OWL, and XML Schema. For more cf.: http://protege.stanford.edu/

10. Protege Tutorial Some tutorials: http://protege.stanford.edu/publications/ontology_development/ontology101-noy- mcguinness.html http://www-smi.stanford.edu/projects/protege/amia2003/AMIA2003Tutorial.ppt http://protege.stanford.edu/doc/users.html#tutorials

11. Some Important Existing Ontologies Cyc: http://www.opencyc.org/ http://www.cycfoundation.org/ Suggested Upper Merged Ontology (SUMO): http://www.ontologyportal.org/ WordNet Lexical reference system: http://wordnet.princeton.edu/ Gene Ontology: http://www.geneontology.org/ Foundational, Core and Linguistic Ontologies: http://www.loa-cnr.it/Ontologies.html

12. Last but not Least Ontoverse: www.ontoverse.org http://www.ontoverse.org/de/grundlagen/grundlagen_1.html