CIS Monthly Seminar – Software Engineering and Knowledge Management IS Enterprise Modeling Ontologies Presenter : Dr. S. Vasanthapriyan Senior Lecturer in CS & Software Engineering Department of Computing & Information Systems Sabaragamuwa University of Sri Lanka /

Department of CIS PhD Practice : Knowledge Management and Software Engineering Reading Materials for this chapter  Reference to Read 1.Baader, F., Horrocks, I., & Sattler, U. (2005). Description logics as ontology languages for the semantic web. In Mechanizing Mathematical Reasoning (pp ). Springer Berlin Heidelberg. 2

Department of CIS PhD Practice : Knowledge Management and Software Engineering Description Logics  Description logics (DLs) are a family of knowledge representation languages (are formal languages used to construct ontologies) that can be used to represent the knowledge of an application domain in a structured and formally well-understood way.formal languagesontologies  Description logics are formal languages designed for knowledge representation and reasoning, and most of these are decidable fragments of FOL.  Assume that we want to define the concept of “A man that is married to a doctor, and all of whose children are either doctors or professors.” 3

Department of CIS PhD Practice : Knowledge Management and Software Engineering Description Logics  Description logics are formal languages designed for knowledge representation and reasoning, and most of these are decidable fragments of FOL.  Knowledge Representation (KR) - Application oriented - Represent ‘knowledge’ in some way  Automated Reasoning, Modal Logic – Had theorems and algorithms 4

Department of CIS PhD Practice : Knowledge Management and Software Engineering DL Syntax 5

Department of CIS PhD Practice : Knowledge Management and Software Engineering DL Syntax 6

Department of CIS PhD Practice : Knowledge Management and Software Engineering Quantifiers and Negation 7

Department of CIS PhD Practice : Knowledge Management and Software Engineering DL Syntax 8

Department of CIS PhD Practice : Knowledge Management and Software Engineering DL Syntax 9

Department of CIS PhD Practice : Knowledge Management and Software Engineering DL Syntax 10

Department of CIS PhD Practice : Knowledge Management and Software Engineering DL Syntax 11

Department of CIS PhD Practice : Knowledge Management and Software Engineering Class/Concept Constructors  for C a concept (class); P a role (property); x an individual name

Department of CIS PhD Practice : Knowledge Management and Software Engineering Ontology Axioms  An Ontology is usually considered to be a TBox - but an OWL ontology is a set of TBox and ABox axioms

Department of CIS PhD Practice : Knowledge Management and Software Engineering Knowledge base  A description logic knowledge base is the equivalent of a theory in first-order logic or an ontology in OWL.description logicOWL  Definition (Knowledge Base). A DL knowledge base K is a triple T, A, R whereDL - T is a set of terminological axioms (TBox)TBox - A is a set of assertion axioms (ABox)ABox - R is a role box (RBox)RBox 14

Department of CIS PhD Practice : Knowledge Management and Software Engineering Basic Building Blocks of DL Ontologies  DL provide means to model the relationships between entities in a domain of interest.  In DLs there are three kinds of entities: concepts, roles and individual names. - Concepts represent sets of individuals, roles represent binary relations between the individuals, and individual names represent single individuals in the domain.  An ontology modelling the domain of people and their family relationships might use concepts such Parent to represent the set of all parents and Female to represent the set of all female individuals, roles such as parentOf to represent the (binary) relationship between parents and their children, and individual names such as Muru and Geetha to represent the individuals Muru and Geetha. 15

Department of CIS PhD Practice : Knowledge Management and Software Engineering ABox - Concept assertions  ABox axioms capture knowledge about named individuals, i.e., the concepts to which they belong and how they are related to each other. The most common ABox axioms are concept assertions such as Mother( Geetha) which asserts that Geetha is a mother or, more precisely, that the individual named Geetha is an instance of the concept Mother. 16

Department of CIS PhD Practice : Knowledge Management and Software Engineering Abox- Role assertions  Role assertions describe relations between named individuals. The assertion parentOf( Geetha, Muru) - states that Geetha is a parent of Muru or, more precisely, that the individual named Geetha is in the relation that is represented by parentOf to the individual named Muru. 17

Department of CIS PhD Practice : Knowledge Management and Software Engineering Abox- Concept and Role assertions  The ABox contains extensional knowledge about the domain of interest, that is, assertions about individuals, usually called membership assertions. For example, Female ⊓ Person(Geetha)  states that the individual Geetha is a female person. Given the above definition of woman, one can derive from this assertion that Geetha is an instance of the concept Woman.  Similarly, hasChild(Geetha, Muru)  specifies that Geetha has Muru as a child. Assertions of the first kind are also called concept assertions, while assertions of the second kind are also called role assertions. 18

Department of CIS PhD Practice : Knowledge Management and Software Engineering Expressing Terminological Knowledge with TBox Axioms  The TBox contains intensional knowledge in the form of a terminology (hence the term “TBox,” but “taxonomy” could be used as well) and is built through declarations that describe general properties of concepts.  TBoxes are usually thought of as having a lattice-like structure; this mathematical structure is entailed by the subsumption relationship. 19

Department of CIS PhD Practice : Knowledge Management and Software Engineering Expressing Terminological Knowledge with TBox Axioms  The basic form of declaration in a TBox is a concept definition, that is, the definition of a new concept in terms of other previously defined concepts. For example, a woman can be defined as a female person by writing this declaration: Woman ≡ Person ⊓ Female  Such a declaration is usually interpreted as a logical equivalence, which amounts to providing both sufficient and necessary conditions for classifying an individual as a woman. 20

Department of CIS PhD Practice : Knowledge Management and Software Engineering A terminology (TBox) with concepts about family relationships. 21

Department of CIS PhD Practice : Knowledge Management and Software Engineering A terminology (TBox) with concepts about family relationships. 22

Department of CIS PhD Practice : Knowledge Management and Software Engineering Examples 23

Department of CIS PhD Practice : Knowledge Management and Software Engineering Ontology language  formal languages used to construct ontologies. formal languagesontologies - are commonly based on either first-order logic or on description logic.first-order logicdescription logic - Classification by syntax - Classification by structure (logic type) 24

Department of CIS PhD Practice : Knowledge Management and Software Engineering Traditional syntax ontology languages  Common Logic - and its dialects  CycL  DOGMA (Developing Ontology-Grounded Methods and Applications)  F-Logic (Frame Logic)  KIF (Knowledge Interchange Format)  Ontolingua based on KIF  KL-ONE  KM programming language  LOOM (ontology)  OCML (Operational Conceptual Modelling Language)  OKBC (Open Knowledge Base Connectivity)  PLIB (Parts LIBrary)  RACER 25

Department of CIS PhD Practice : Knowledge Management and Software Engineering Markup ontology languages  These languages use a markup scheme to encode knowledge, most commonly with XML.markupXML - DAML+OIL DAML+OIL - Ontology Inference Layer (OIL) Ontology Inference Layer - Web Ontology Language (OWL) Web Ontology Language - Resource Description Framework (RDF) Resource Description Framework - RDF Schema (RDFS) RDF Schema - SHOE SHOE 26

Department of CIS PhD Practice : Knowledge Management and Software Engineering Description logic-based - KL-ONE KL-ONE - RACER RACER - OWL. OWL 27

Department of CIS PhD Practice : Knowledge Management and Software Engineering Thank you 28