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Knowledge Representation Part I Ontology Jan Pettersen Nytun Knowledge Representation Part I, JPN, UiA 1 Outline S P O • Knowledge • Ontology – Ontology in philosophy – Ontology in computer science – Different types of ontologies • Levels of ontological precision Knowledge Representation Part I, JPN, UiA 2 facts/understanding about a particular subject a symbol or thing which represents something else (refers to, stands for) is is Knowledge Representation AI require when to use computer-understandable form when we can not use the “original”, like things in the natural world or concepts Knowledge Representation Part I, JPN, UiA 3 S P O From Wikipedia, the free encyclopedia (Knowledge representation and reasoning) Knowledge Representation (KR) is an area of artificial intelligence research aimed at representing knowledge in symbols to facilitate inferencing from those knowledge elements, creating new elements of knowledge. Knowledge Representation Part I, JPN, UiA 4 S P O Knowledge Base • A database for knowledge management • It provides means for information to be: – Collected – Organized – Shared, searched and utilized (new information may be inferred) Knowledge Representation Part I, JPN, UiA 5 S P O Knowledge Engineering • Get knowledge about some subject and represent it in a computable form for some purpose. • The knowledge engineer tells the system what is true. Knowledge Representation Part I, JPN, UiA 6 S P O Knowledge Engineering Continues… The system knows how to infer new facts and solutions – the user may form questions and then the system gives answers. Knowledge Base Asserted Statements Asserted Statements Inferred Statements entailment inferred statements comes as a logical consequence of the asserted statements and logical rules Knowledge Representation Part I, JPN, UiA Inferred Statements 7 Outline S P O • Knowledge • Ontology – Ontology in philosophy – Ontology in computer science – Different types of ontologies • Levels of ontological precision Knowledge Representation Part I, JPN, UiA 8 S P O What is an Ontology in Regard to Philosophy? From Wikipedia, the free encyclopedia 9 S P O What is an Ontology in Regard to Philosophy? Continues… Smith [1] the essence of ontology: “provide a definitive and exhaustive classification of entities in all spheres of being.” 10 S P O What is an Ontology in Computer Science? Knowledge represented in a formal way: - a hierarchy of concepts within a domain, - a shared vocabulary to denote the types, - properties and interrelationships of those concepts. 11 S P O What is an Ontology in Computer Science? … Continues An ontology is a specification of a conceptualization that is designed for reuse across multiple applications and implementations. …a specification of a conceptualization is a written, formal description of a set of concepts and relationships in a domain of interest. Peter Karp (2000) Bioinformatics 16:269 12 Types of Ontologies [Ref. Medical Informatics: Knowledge Management and Data Mining in Biomedicine]: From Wikipedia, the free encyclopedia: In computer science and information science, an ontology is… a practical application of philosophical ontology. 13 S P O Types of Ontologies… Continues An upper ontology - also called top-level ontology or foundation ontology - describes the most general concepts that are the same across all knowledge domains (e.g., Entity). Knowledge Representation Part I, JPN, UiA 14 S P O Types of Ontologies… Continues [Ref. Medical Informatics: Knowledge Management and Data Mining in Biomedicine]: General ontologies represent knowledge at an intermediate level of detail independently of a specific task… theories of time and space, for example... Knowledge Representation Part I, JPN, UiA 15 S P O Types of Ontologies… Continues [Ref. Medical Informatics: Knowledge Management and Data Mining in Biomedicine]: Domain ontologies represent knowledge about a particular part of the world, such as medicine, and should reflect the underlying reality through a theory of the domain represented. Knowledge Representation Part I, JPN, UiA 16 S P O Types of Ontologies… Continues [Ref. Medical Informatics: Knowledge Management and Data Mining in Biomedicine]: …ontologies designed for specific tasks are called application ontologies. Conversely, reference ontologies are developed independently of any particular purpose… Knowledge Representation Part I, JPN, UiA 17 Descriptive Ontology for Linguistic and Cognitive Engineering S P O Knowledge Representation Part I, JPN, UiA 18 Outline S P O • Knowledge • Ontology – Ontology in philosophy – Ontology in computer science – Different types of ontologies • Levels of ontological precision Knowledge Representation Part I, JPN, UiA 19 S P O Catalog: A list of things. Knowledge Representation Part I, JPN, UiA 20 S P O From Wikipidia: A Glossary, also known as a vocabulary,… is an alphabetical list of terms in a particular domain of knowledge with the definitions for those terms. S P O A Taxonomy – also called a class hierarchy - organizes its data into categories and subcategories. S P O In general usage, a thesaurus is a reference work that lists words grouped together according to similarity of meaning (containing synonyms and sometimes antonyms). From Wikipidia: S P O From Wikipidia: A database schema …is a structure described in a formal language… and refers to the organization of data as a blueprint of how a database is constructed (e.g., database tables for Relational Databases). In mathematics, an axiomatic system is any set of axioms from which some or all axioms can be used in conjunction to logically derive theorems. A mathematical theory consists of an axiomatic system and all its derived theorems. From Wikipidia: S P O Ontology Engineering as a Disiplin Example of Process Decide Scope Reuse? Enumerate Terms Studies the methods and methodologies for building ontologies. Define Classes Define Properties Define Constraints Knowledge Representation Part I, JPN, UiA Create Instances 26 S P O References [1] Book: David Poole and Alan Mackworth, Artificial Intelligence: Foundations of Computational Agents, Cambridge University Press, 2010, http://artint.info/ Sowa, John F. (2000) Knowledge Representation: Logical, Philosophical, and Computational Foundations, Brooks/Cole Publishing Co., Pacific Grove, CA. Artificial Intelligence: Structures and Strategies for Complex Problem Solving (AddisonWesley), George F. Luger Smith Barry. Accessed 24th of March, 2013, Ontology: Philosophical and Computational. http: //ontology.buffalo.edu/smith/articles/ontologies.htm Quine WVO. On What There Is. Review of Metaphysics 1948;p. 21–38. Knowledge Representation Part I, JPN, UiA 27