ece 627 intelligent web: ontology and beyond lecture 2: ontology - basics

ontology a branch of metaphysics relating to the nature and relations of being a particular theory about the nature of being or the kinds of existence ece 627, winter'13

ontology & history tree of Porphyry Supreme: SUBSTANCE Differentiae: material immaterial Subordinate: BODY SPIRIT Differentiae: animate inanimate Subordinate: LIVING MINERAL Differentiae: sensitive insensitive Subordinate: ANIMAL PLANT Differentiae: rational irrational Subordinate: HUMAN BEAST Individuals: Socrates Plato Aristotle etc. ece 627, winter'13

ontology generic ece 627, winter'13

ontology domain-based the subject of ontology is the study of the categories of things that exist or may exist in some domain ece 627, winter'13

ontology domain-based the product of such a study, called an ontology, is a catalog of the types of things that are assumed to exist in a domain of interest from the perspective of a person who uses a specific language for the purpose of talking about the domain ece 627, winter'13

ontology domain-based – definition 1 a formal, explicit specification of a shared conceptualization [T.Gruber, 1993] ece 627, winter'13

ontology domain-based conceptualization refers to an abstract model of phenomena in the world by having identified the relevant concepts of those phenomena explicit means that the type of concepts used, and the constraints on their use are explicitly defined ece 627, winter'13

ontology domain-based formal refers to the fact that the ontology should be machine readable shared reflects that ontology should capture consensual knowledge accepted by the communities ece 627, winter'13

ontology domain-based – definition 2 (W3C) ontology is a term borrowed from philosophy that refers to the science of describing the kinds of entities in the world and how they are related ece 627, winter'13

ontology … description of … classes (“things”) in the various domains of interest relationships among those “things” properties (attributes) that “things” should possess ece 627, winter'13

ontology example ece 627, winter'13

ontology example ece 627, winter'13

ontology vs taxonomy taxonomy the study of the general principles of scientific classification – systematics classification – especially – orderly classification of plans and animals according to their presumed natural relationships ece 627, winter'13

ontology vs taxonomy taxonomy classifies terms hierarchically, using (generalization, is-a, or type-of) relationship - no other relationships - no attributes/features describing terms ece 627, winter'13

ontology vs taxonomy (example) - Linnaean living being taxonomy Kingdom: animalia Filo: chordata Subfilo: vertebrata Class: mamalia Subclass: theria Order: primata Suborder: anthropoidea Family: hominidae Genera: homo Species: sapiens ece 627, winter'13

ontology vs taxonomy (example) - directory structure in a personal computer ece 627, winter'13

ontology vs thesauri thesauri contains a set of relationships among concepts, organized in a taxonomic way it is a taxonomy with a set of semantic (binary) relationships, such as, equivalence, inverse, and association ece 627, winter'13

ontology vs thesauri not sufficient to model other (part-of, member-group, cause-effect, …) aspects of real world the most popular thesaurus - WordNet ece 627, winter'13

ontology vs thesauri - WordNet ece 627, winter'13

ontology vs thesauri - WordNet ece 627, winter'13

ontology vs thesauri - WordNet ece 627, winter'13

ontology ”unique” properties – 1 strict subconcept hierarchy organization of terms must follow the generalization relationship – is-a, type-of relationship ece 627, winter'13

ontology ”unique” properties – 2 ambiguity-free interpretation of meanings and relationships users may define properties (with values restricted to certain domains) and more expressive relationships (part-of, ……………) ece 627, winter'13

ontology ”unique” properties – 3 the use of a controlled, finite, but extensible vocabulary ece 627, winter'13

ontology classification according to semantic spectrum based on the internal structure and contents of ontolgoies depends on the complexity and sophistication of the elements the spectrum ranges from informal catalogues of terms to sophisticated ontologies ece 627, winter'13

ontology classification according to semantic spectrum controlled vocabularies (finite lists of terms) glossaries (lists of terms whose meaning is described in natural language) Thesauri (lists of terms … and specific relationships between the terms) ece 627, winter'13

ontology classification according to semantic spectrum informal is-a hierarchies (hierarchies that use generalization relationships in an informal way – not rigorously) formal is-a hierarchies (hierarchies that fully respect the generalization relationships) ece 627, winter'13

ontology classification according to semantic spectrum frames (models that include classes and properties; the primitives of the frame model are classes, or frames, that have properties called slots or attributes; slots may contain default values, refer to other frames, or contain different methods) ece 627, winter'13

ontology classification according to semantic spectrum ontologies that express value restrictions (contain constructs for restricting the values the class properties can assume) ontologies that express logical restrictions (allow first-order logic restrictions to be expressed) ece 627, winter'13

ontology classification according to ontology generality upper-level ontologies (describe generic concepts, such as space, time, events …) domain ontologies (describe vocabulary pertaining to a given domain, by specializing the concepts provided by the upper-level ontology) ece 627, winter'13

ontology classification according to ontology generality task ontologies (describe vocabulary required to perform generic tasks or activities, by specializing the concepts provided by the upper-level ontology) applications ontologies (describe vocabulary of a specific application, whose concepts correspond to the roles performed by entities in a given domain while performing some task or activity) ece 627, winter'13

ontology classification according to represented info based on “orthogonal”, to previous slides, classification knowledge-representation ontologies (provide primitive modeling elements – classes, subclasses, value, …) generic and common use ontologies (represent common-sense knowledge that can be used in different domains; vocabulary that relates classes, events, space, causality, and behavior) ece 627, winter'13

ontology classification according to represented info upper ontologies (describe general concepts, for example SUMO) ece 627, winter'13

ontology classification according to represented info domain ontologies (offer concepts that can be reused in a specific domain – medical, law, …; sth between upper and domain ontologies) task ontologies (describe vocabulary related to a task or activity) ece 627, winter'13

ontology classification according to represented info domain-task ontologies (are task ontologies that can be reused in one specific domain) method ontologies (provide definitions for concepts and relationships relevant to a process) application ontologies (contain all necessary concepts to model the application in question) ece 627, winter'13

ontology description languages 1967 – markup language (structure of documents with help of tags) SGML – Standard Generalization Markup Language 1989 – HTML (HyperText Markup Language) XML (Extensible Markup Language) ece 627, winter'13

ontology description languages RDF (Resource Markup Language) – representing information about resources in the web RDF Schema SHOE (Simple HTML Ontology Extension) Oil (Ontology Inference Layer) DAML (DARPA Agent Markup Language) ece 627, winter'13

ontology description languages 2001 – DMAL+Oil Feb 10th, 2004 – OWL (Web Ontology Language) ece 627, winter'13