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

lecture 2: ontology - basics

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ontology & history ontology tree of Porphyry generic

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.

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ontology ontology domain-based domain-based

the subject of ontology is the study of the categories the product of such a study, called an ontology, is a of things that exist or may exist in some domain 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

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conceptualization refers to an abstract model of a formal, explicit specification of a shared phenomena in the world by having identified the conceptualization relevant concepts of those phenomena

explicit means that the type of concepts used, and [T.Gruber, 1993] the constraints on their use are explicitly defined

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ontology ontology domain-based domain-based – definition 2 (W3C)

formal refers to the fact that the ontology should be machine readable ontology is a term borrowed from philosophy that refers to the science of describing the kinds of shared reflects that ontology should capture entities in the world and know they are related consensual knowledge accepted by the communities

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ontology ontology … description of … example

! classes (“things”) in the various domains of interest ! relationships among those “things” ! properties (attributes) that “things” should possess

ece#627,#winter'13# 11# of#39# ece#627,#winter'13# 12# of#39# ontology ontology example 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

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ontology ontology vs taxonomy vs taxonomy (example)

- Linnaean living being taxonomy taxonomy classifies terms hierarchically, using Kingdom: animalia (generalization, is-a, or type-of) relationship Filo: chordata Subfilo: vertebrata - no other relationships Class: mamalia - no attributes/features describing terms Subclass: theria Order: primata Suborder: anthropoidea Family: hominidae Genera: homo Species: sapiens ece#627,#winter'13# 15# of#39# ece#627,#winter'13# 16# of#39#

ontology ontology vs taxonomy (example) vs thesauri

- directory structure in a personal computer 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

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not sufficient to model other (part-of, member- group, cause-effect, …) aspects of real world

the most popular thesaurus - WordNet

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ontology ontology vs thesauri - WordNet vs thesauri - WordNet

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ontology ontology unique properties – 1 unique properties – 2

strict subconcept hierarchy ambiguity-free interpretation of meanings and organization of terms must follow the generalization relationships relationship – is-a, type-of relationship users may define properties (with values restricted to certain domains) and more expressive relationships (part-of, ……………)

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based on the internal structure and contents of the use of a controlled, finite, but extensible ontolgoies

vocabulary depends on the complexity and sophistication of the elements

the spectrum ranges from informal catalogues of terms to sophisticated ontologies

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ontology ontology classification according to semantic spectrum classification according to semantic spectrum

- controlled vocabularies (finite lists of terms) - informal is-a hierarchies (hierarchies that use - glossaries (lists of terms whose meaning is generalization relationships in an informal way – described in natural language) not rigorously) - Thesauri (lists of terms … and specific relationships - formal is-a hierarchies (hierarchies that fully between the terms) respect the generalization relationships)

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ontology ontology classification according to semantic spectrum classification according to semantic spectrum

- frames (models that include classes and properties; - ontologies that express value restrictions (contain the primitives of the frame model are classes, or constructs for restricting the values the class frames, that have properties called slots or properties can assume) attributes; slots may contain default values, refer - ontologies that express logical restrictions (allow to other frames, or contain different methods) first-order logic restrictions to be expressed)

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- upper-level ontologies (describe generic concepts, - task ontologies (describe vocabulary required to such as space, time, events …) perform generic tasks or activities, by specializing - domain ontologies (describe vocabulary pertaining the concepts provided by the upper-level ontology) to a given domain, by specializing the concepts - applications ontologies (describe vocabulary of a provided by the upper-level ontology) specific application, whose concepts correspond to the roles performed by entities in a given domain while performing some task or activity)

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ontology ontology classification according to represented info classification according to represented info

based on orthogonal, to previous slides, - upper ontologies (describe classification general concepts, - knowledge-representation ontologies (provide for example SUMO) 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# 33# of#39# ece#627,#winter'13# 34# of#39#

ontology ontology classification according to represented info classification according to represented info

- domain ontologies (offer concepts that can be - domain-task ontologies (are task ontologies that reused in a specific domain – medical, law, …; sth can be reused in one specific domain) between upper and domain ontologies) - method ontologies (provide definitions for concepts - task ontologies (describe vocabulary related to a and relationships relevant to a process) task or activity) - application ontologies (contain all necessary concepts to model the application in question)

ece#627,#winter'13# 35# of#39# ece#627,#winter'13# 36# of#39# ontology ontology description languages description languages

1967 – markup language (structure of documents RDF (Resource Markup Language) – representing with help of tags) information about resources in the web SGML – Standard Generalization Markup Language RDF Schema 1989 – HTML (HyperText Markup Language) SHOE (Simple HTML Ontology Extension) XML (Extensible Markup Language) Oil (Ontology Inference Layer) DAML (DARPA Agent Markup Language)

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ontology description languages

2001 – DMAL+Oil Feb 10th, 2004 – OWL ()

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