Semantic Web - Ontologies Sameer Totey 9/18/2018 CSCI 7818 - Web Infrastructure, Services, and Applications

CSCI 7818 - Web Infrastructure, Services, and Applications What is Ontology Branch of Philosophy that studies nature of existence Specification of a conceptualization Document or file that formally defines relations among terms Shared understanding of some domain of interest 9/18/2018 CSCI 7818 - Web Infrastructure, Services, and Applications

CSCI 7818 - Web Infrastructure, Services, and Applications This picture is from Tutorial on “Development and applications of Ontologies” by Alexander Maedche 9/18/2018 CSCI 7818 - Web Infrastructure, Services, and Applications

CSCI 7818 - Web Infrastructure, Services, and Applications 9/18/2018 CSCI 7818 - Web Infrastructure, Services, and Applications

What is Ontology for Web ? A Taxonomy which defines classes of objects and relations among them A set of inference rules (Classes subclasses and relations among entities) 9/18/2018 CSCI 7818 - Web Infrastructure, Services, and Applications

CSCI 7818 - Web Infrastructure, Services, and Applications Why Ontologies? Lack of a shared understanding leads to poor communication Disparate modeling paradigms, languages and software tools limit Interoperability Knowledge Sharing and reuse 9/18/2018 CSCI 7818 - Web Infrastructure, Services, and Applications

CSCI 7818 - Web Infrastructure, Services, and Applications Theory Usually Ontology structure is represented as a 5 Tuple O = (C,R, H, rel, A) Disjoint Sets C and R are concept identifiers and relation identifiers respectively H is the concept hierarchy. Also called Taxonomy. H(C1,C2) means C1 is subconcept of C2. H is a directed transitive relation. Rel is a function that relates concept non-taxonomically, rel : R  C X C A is a set of ontology Axioms, expressed in an logical language like first order logic. 9/18/2018 CSCI 7818 - Web Infrastructure, Services, and Applications

CSCI 7818 - Web Infrastructure, Services, and Applications Ontology Engineering The task of developing an ontology is a typical knowledge acquisition task involving Kickoff Refinement Evaluation Maintenance 9/18/2018 CSCI 7818 - Web Infrastructure, Services, and Applications

CSCI 7818 - Web Infrastructure, Services, and Applications Languages There are several representation languages in the AI (machine learning, natural language processing, knowledge representation etc) community based on FOL like Frame Logic Loom Ontololingua etc. Web needs XML based language : defining a language on top of XML syntax SHOE (SHOE is an HTML-based knowledge representation language) Simple HTML Ontology Extention. XOL (Ontology Exchange Language) OML (Ontology markup language) RDFS (Resourse description framework scheme language) OIL (Ontology Interchange Language) DAML (DARPA Agent markup language) 9/18/2018 CSCI 7818 - Web Infrastructure, Services, and Applications

CSCI 7818 - Web Infrastructure, Services, and Applications Editors Tools that help create ontologies and metadata that can be used by multiple agents: Protégé WebOnto OilEd ONTOEdit 9/18/2018 CSCI 7818 - Web Infrastructure, Services, and Applications

CSCI 7818 - Web Infrastructure, Services, and Applications Related issues: Higher order logic based inference engines – Needed but not feasible First order logic based inference engines – feasible but limited expressive power, FOL is semi-decidable some inferences are computationally intractable Interoperability Bremer Semantic Translation project SKC (Stanford Scalable Knowledge Composition) project 9/18/2018 CSCI 7818 - Web Infrastructure, Services, and Applications

CSCI 7818 - Web Infrastructure, Services, and Applications References http://www.fzi.de/wim [Development and applications of Ontologies] tutorial www.sematicweb.org www.ontologyworks.com 9/18/2018 CSCI 7818 - Web Infrastructure, Services, and Applications

CSCI 7818 - Web Infrastructure, Services, and Applications 9/18/2018 CSCI 7818 - Web Infrastructure, Services, and Applications