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Understanding OWL and Security in Semantic Web: Lecture 7 by Dr. Bhavani Thuraisingham

This lecture provides a comprehensive overview of ontologies, focusing on the Web Ontology Language (OWL) and associated security issues. It explains why RDF is inadequate for expressing complex semantics and explores how ontologies play a crucial role in defining security policies. The lecture covers OWL's features, syntax, semantics, and its practical applications in managing semantic web security. Key security concepts include access control, role-based access policies, and privacy constraints. Join Dr. Bhavani Thuraisingham as she navigates the intersection of ontology and security.

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Understanding OWL and Security in Semantic Web: Lecture 7 by Dr. Bhavani Thuraisingham

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  1. Building Trustworthy Semantic Webs Lecture #7: OWL (Web Ontology Language) and Security Dr. Bhavani Thuraisingham September 2006

  2. Objective of the Unit • This unit will provide an overview of ontologies, OWL and then discuss some security issues

  3. Outline of the Unit • What are ontologies • Why is RDF not sufficient? • What are the security issues for ontologies • What is OWL? • OWL Syntax and Semantics • Summary and Directions

  4. Ontology • Common definitions for any entity, person or thing • Several ontologies have been defined and available for use • Defining common ontology for an entity is a challenge • Mappings have to be developed for multiple ontologies • Specific languages have been developed for ontologies

  5. Why RDF is not sufficient? • RDF was developed as XML is not sufficient to specify semantics • E.g., class/subclass relationship • RDF has issues also • Cannot express several other properties such as Union, Interaction, relationships, etc • Need a richer language • Ontology languages were developed by the semantic web community for this purpose • Essentially RDF is not sufficient to specify ontologies

  6. Security and Ontology • Ontologies used to specify security policies • Example: OWL to specify security policies • Choice between XML, RDF, OWL, Rules ML, etc. • Security for Ontologies • Access control on Ontologies • Give access to certain parts of the Ontology

  7. OWL: Background • It’s a language for ontologies and relies on RDF • DARPA (Defense Advanced Research Projects Agency) developed early language DAML (DARPA Agent Markup Language) • Europeans developed OIL (Ontology Interface Language) • DAML+OIL combines both and was the starting point for OWL • OWL was developed by W3C

  8. OWL Features • Subclass relationship • Class membership • Equivalence of classes • Classification • Consistency (e.g., x is an instance of A, A is a subclass of B, x is not an instance of B) • Three types of OWL: OWL-Full, OWL-DL, OWL-Lite • Automated tools for managing ontologies • Ontology engineering

  9. OWL Specification (e.g., Classes) < owl: Class rdf: about = “#associateProfessor”> <owl: disjointWith rdf: resource “#professor”/> <owl: disjointWith rdf: resource = #assistantProfessor”/> </owl:Class> <owl: Class rdf: ID = “faculty”> <owl: equivalentClass rdf: resource = “academicStaffMember”/> </owl: Class> Faculty and Academic Staff Member are the same Associate Professor is not a professor Associate professor is not an Assistant professor

  10. OWL Specification (e.g., Property) Courses are taught by Academic staff members < owl: ObjectProperty rdf: about = “#isTaughtby”> <rdfs domain rdf: resource = “#course”/> <rdfs: range rdf: resource = “#academicStaffMember”/> <rdfs: subPropertyOf rdf: resource = #involves”/> </owl: ObjectProperty>

  11. OWL Specification (e.g., Property Restriction) All first year courses are taught only by professors < owl: Class rdf: about = “#”firstyearCourse”> <rdfs: subClassOf> <owl: Restriction> <owl: onProperty rdf: resource = “#isTaughtBy”> <owl: allValuesFrom rdf: resource = #Professor”/> </rdfs: subClassOf> </owl: Class>

  12. Policies in OWL • How can policies be specified? • Should policies be specified as shown in the examples, extensions to OWL syntax? • Should policies be specified as OWL documents? • Is there an analogy to XPath expressions for OWL policies? • <policy-spec cred-expr = “//Professor[department = ‘CS’]” target = “annual_ report.xml” path = “//Patent[@Dept = ‘CS’]//Node()” priv = “VIEW”/>

  13. Policies in OWL: Example < owl: Class rdf: about = “#associateProfessor”> <owl: disjointWith rdf: resource “#professor”/> <owl: disjointWith rdf: resource = #assistantProfessor”/> Level = L1 </owl:Class> <owl: Class rdf: ID = “faculty”> <owl: equivalentClass rdf: resource = “academicStaffMember”/> Level = L2 </owl: Class>

  14. Example Policies • Temporal Access Control • After 1/1/05, only doctors have access to medical records • Role-based Access Control • Manager has access to salary information • Project leader has access to project budgets, but he does not have access to salary information • What happens is the manager is also the project leader? • Positive and Negative Authorizations • John has write access to EMP • John does not have read access to DEPT • John does not have write access to Salary attribute in EMP • How are conflicts resolved?

  15. Privacy Policies • Privacy constraints processing • Simple Constraint: an attribute of a document is private • Content-based constraint: If document contains information about X, then it is private • Association-based Constraint: Two or more documents taken together is private; individually each document is public • Release constraint: After X is released Y becomes private • Augment a database system with a privacy controller for constraint processing

  16. Access Control Strategy • Subjects request access to OWL documents under two modes: Browsing and authoring • With browsing access subject can read/navigate documents • Authoring access is needed to modify, delete, append documents • Access control module checks the policy based and applies policy specs • Views of the document are created based on credentials and policy specs • In case of conflict, least access privilege rule is enforced • Works for Push/Pull modes • Query Modification?

  17. System Architecture for Access Control User Pull/Query Push/result RDF- Access RDF-Admin Admin Tools Credential base Policy base OWL Documents

  18. OWL Databases • Data is presented as OWL documents • Query language? OWL=QL? • Query optimization (depends on query language) • Managing transactions on OWL documents • Metadata management: OWL schemas? • Access methods and index strategies • OWL security and integrity management

  19. Inference/Privacy Control Interface to the Semantic Web Technology By UTD Inference Engine/ Rules Processor (Reasoning in OWL?) Policies Ontologies Rules OWL Documents Web Pages, Databases OWL Data Management

  20. Summary and Directions • Ontologies are a necessity for the web • OWL is getting recognition; several other ontology languages (DAML, OIL, etc.) • Very little work on security and ontologies? • How can we specify the policies in OWL? • How can query modification be carried out for OWL documents? • Design access control for OWL databases

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