Semantic Web Rule Language

1. Semantic Web Rule Language Presented by: Tejaswi Billa Koti November 16,2009

2. Introduction What is Semantic Web? Semantic Web is an evolving development of the World Wide Web in which the meaning (semantics) of information and services on the web is defined

3. Purpose • The semantic web is a vision of information that is understandable by computers, so that they can perform more of the tedious work involved in finding, sharing, and combining information on the web

4. Components of Semantic Web • Semantic web comprises the standards and tools of XML, XML Schema, RDF, RDF Schema and OWL that are organized in the Semantic Web Stack. • Semantic Web Stack.

5. “RULES” Rules are useful to represent: • Some kinds of ontologies • Mapping between different ontologies • Between knowledge bases expressed in one ontology to another

6. “ONTOLOGY” • In computer science and information science, an ontology is a formal representation of a set of concepts within a domain and the relationships between those concepts. It is used to reason about the properties of that domain, and may be used to define the domain.

7. Semantic Web Rule Language(S W R L) • SWRL -- RULE LANGUAGE OF SEMANTIC WEB • SWRL is a proposal to combine RULES and Ontologies SWRL = Rules + Ontologies Rules correspond to RuleML Ontologies correspond to OWL-DL

8. Why a Rule Language?? A Rule Language is needed for several purposes: Existing Rule sets can be reused Expressivity can be added to OWL It is easier to read and write rules with a Rule Language Background(True in some cases but not always)

9. Syntax for SWRL • Syntax extends the abstract syntax of OWL described in the OWL semantics and Abstract Syntax documents. • Abstract Syntax is specified here by a version of Extended BNF(EBNF), very similar to the one used for XML.

10. Syntax….(Contd…) • Terminals are quoted; • Non-Terminals are bold and not quoted; • Alternatives are separated by vertical bar (|) or given in different productions; • Components that occur at most once are enclosed in Square brackets([….]); and the one’s which occur more than once are enclosed in Flower brackets({……});

11. Rules In the Abstract Syntax OWL Ontology AxiomsFacts Ex: subClass Axioms, equivalentClass Axioms axiom::=rule

12. A RULE AXIOM **rule ::= 'Implies(' [ URIreference ] { annotation } antecedent consequent ')' **antecedent ::= 'Antecedent(' { atom } ')‘ **consequent ::= 'Consequent(' { atom } ')' Consequent (HEAD) Antecedent (BODY)

13. Informally: A RULE can be read as a meaning that if the Antecedent holds(“is true”) then the Consequent must also hold(“also true”)

14. Some Important Things • Rules with empty Antecedent is treated as trivially holding(“true”). • Non-empty Antecedents and Consequents hold iff, all of their constituent atoms hold i.e. they are treated as CONJUNCTION of their atoms.

15. Atom Description Atoms may refer to individuals, data literals, individual variables or data variables atom ::= description '(' i-object ')' | dataRange '(' d-object ')' | individualvaluedPropertyID '(' i-object i-object ')' | datavaluedPropertyID '(' i-object d-object ')‘ | sameAs '(' i-object i-object ')‘ | differentFrom '(' i-object i-object ')' | builtIn '(' builtinID { d-object } ')' builtinID ::= URIreference

16. Atoms can be of the form C(x), where C is an OWL description or data range P(x,y), where P is an OWL property sameAs(x,y) differentFrom(x,y), or builtIn(r,x,...) where r is a built-in relation,

17. NEED FOR HUMAN READABLE SYNTAX

18. Syntax of Human Readable Form Antecedent  Consequent where both antecedent and consequent are conjunctions of atoms written a1 ∧ ... ∧ an ** Variables are written in the standard format (?x)

19. Example: • parent(?x,?y) ∧ brother(?y,?z) ⇒ uncle(?x,?z)

20. SAFE SWRL Rules: • The Safety Condition of the SWRL Rules means, • To add additional Expressive Power • To maintain Decidability at the same time.

21. SWRL Built-Ins • It will provide the flexibility for various implementations to select the modules to be supported with each version of SWRL. • SWRL's built-ins approach is also based on the reuse of existing built-ins in Xquery and XPath, which are themselves based on XML Schema Part 2: Datatypes. • This system of built-ins should also help in the interoperation of SWRL with other Web formalisms by providing an extensible, modular built-ins infrastructure for Semantic Web Languages, Web Services, and Web applications. • SWRL built-ins are used in builtin atoms. For example, swrlx:builtinAtom identifies a built-in using the swrlx:builtin attribute and lists its arguments as subelements. • Swrl built-ins are identified using the http://www.w3.org/2003/11/swrlb namespace. • Please Refer: http://www.w3.org/Submission/SWRL/

22. Reasoner Supports for SWRL • Examples of some Reasoners supporting SWRL are: • SWRL TAB • Pellet • RacerPro

23. References • [1]http://en.wikipedia.org/wiki/Ontology_(information_science) • [2] http://www.w3.org/Submission/SWRL/ • [3]http://images.google.com/imgres?imgurl=http://www.dailygalaxy.com/photos/uncategorized/2007/07/05/semantic_web.jpg&imgrefurl=http://www.dailygalaxy.com/my_weblog/2008/07/microscope-acqu.html&usg=__IzvxrGg35SyozKE1DUQwE8DvueQ=&h=334&w=500&sz=287&hl=en&start=18&sig2=0RU0PkZDveD0H_ZzIgCtvQ&um=1&tbnid=jWCbV2Fm3FOqAM:&tbnh=87&tbnw=130&prev=/images%3Fq%3Dsemantic%2Bweb%26hl%3Den%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26sa%3DN%26um%3D1&ei=pusAS6LvKdCztgfV5NWRDg

24. Contact Information • Tejaswi Billa Koti Email: tejaswi.billakoti@utdallas.edu Phone: (972) 510 8784