Dr. Bhavani Thuraisingham

1. Building Trustworthy Semantic Webs Unit #1: Introduction to The Semantic Web Dr. Bhavani Thuraisingham August 2006

2. Objective of the Unit • This unit will provide an overview of the semantic web and discuss the information management technologies for the semantic web • Reference: XML, Databases and the Semantic Web, CRC Press, Thuraisingham, March 2002

3. Outline of the Unit • Semantic Web Overview • Web Data Management and Web Services • XML (eXtensible Markup Language) • RDF (Resource Description Framework) • Information Integration and Ontologies • Rules Processing • Coalition Testbed Suggestion • Directions

4. Semantic Web: Overview • According to Tim Berners Lee, The Semantic Web supports • Machine readable and understandable web pages • Enterprise application integration • Nodes and links that essentially form a very large database Premise: Semantic Web Technologies = XML, RDF, Ontologies, Rules Applications: Web Database Management, Web Services, Information Integration

5. TRUST P R I V A C Y Logic, Proof and Trust Rules/Query Other Services RDF, Ontologies XML, XML Schemas URI, UNICODE Layered Architecture for Dependable Semantic Web • Adapted from Tim Berners Lee’s description of the Semantic Web • Some Challenges: Interoperability between Layers; Security and Privacy cut across all layers; Integration of Services; Composability

6. Privacy Confidentiality Trust Dependability Relationships between Dependability, Confidentiality, Privacy, Trust Dependability: Security, Privacy, Trust, Real-time Processing, Fault Tolerance; also sometimes referred to as “Trustworthiness” Confidentiality: Preventing the release of unauthorized information considered sensitive Privacy: Preventing the release of unauthorized information about individuals considered sensitive Trust: Confidence one has that an individual will give him/her correct information or an individual will protect sensitive information

7. What is XML all about? • XML is needed due to the limitations of HTML and complexities of SGML • It is an extensible markup language specified by the W3C (World Wide Web Consortium) • Designed to make the interchange of structured documents over the Internet easier • Key to XML is Document Type Definitions (DTDs) • Defines the role of each element of text in a formal model • Allows users to bring multiple files together to form compound documents

8. Example XML Document Year: 2002 Asset report Name: U. Of X Assets Patents Equipment Other assets Dept Funds Patent news Name: CS Expenses Contracts ID Author title Grants

9. Specifying User Credentials in XML <Professor credID=“9” subID = “16: CIssuer = “2”> <name> Alice Brown </name> <university> University of X <university/> <department> CS </department> <research-group> Security </research-group> </Professor> <Secretary credID=“12” subID = “4: CIssuer = “2”> <name> John James </name> <university> University of X <university/> <department> CS </department> <level> Senior </level> </Secretary>

10. Specifying Security Policies in XML <? Xml VERSION = “1.0” ENCODING = “utf-8”?> <Policy–base> <policy-spec cred-expr = “//Professor[department = ‘CS’]” target = “annual_ report.xml” path = “//Patent[@Dept = ‘CS’]//Node()” priv = “VIEW”/> <policy-spec cred-expr = “//Professor[department = ‘CS’]” target = “annual_ report.xml” path = “//Patent[@Dept = ‘EE’] /Short-descr/Node() and //Patent [@Dept = ‘EE’]/authors” priv = “VIEW”/> <policy-spec cred-expr = - - - - <policy-spec cred-expr = - - -- </Policy-base> Explantaion: CS professors are entitled to access all the patents of their department. They are entitled to see only the short descriptions and authors of patents of the EE department

11. RDF • Resource Description Framework is the essence of the semantic web • Adds semantics with the use of ontologies, XML syntax • RDF Concepts • Basic Model • Resources, Properties and Statements • Container Model • Bag, Sequence and Alternative

12. Ontology Mappings • 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 including RDF and OIL (Ontology Interface Language)

13. Rules Processing User Interface Manager XML Database Design Tool Constraints during database design operation Constraint Manager Rules/ Constraints Update Processor: Constraints during update operation Query Processor: Constraints during query and release operations XML Document Manager XML Database

14. Rule-Processing (Concluded) Interface to the Semantic Web Technology By W3C Inference Engine/ Rules Processor Policies Ontologies Rules XML, RDF Documents Web Pages, Databases Semantic Web Engine

15. Semantic Web Database Management • Database access through the semantic web • XML, RDF technologies • Query, indexing and transaction management for web databases • E.g., New kinds of transaction models for E-commerce applications • Index strategies for unstructured data • Query languages and data models • XML has become the standard document interchange language • Managing XML/RDF databases on the web • XML-QL, Extensions to XML, Query and Indexing strategies

16. Web Services • Web Services are about services on the web for carrying out many functions including directory management, source location, subscribe and publish, etc. • Web services description language (WSDL) exists for web services specification • Web services architectures have been developed • Challenge now is to compose web services; how do you integrate multiple web services and provide composed web service in a seamless fashion • Ultimate goal is to have web services for information integration

17. Publish Query UDDI Answer Request the service Service providers Web service architecture Service requestor

18. Query UDDI Service requestor BusinessService Secure Web Service Architecture Confidentiality, Authenticity, Integrity BusinessEntity <dsig:Signature> tModel BusinessService PublisherAssertion BindingTemplate Service provider

19. Example Web Service • Publish/Subscribe Service

20. Information Integration • Data Integration: • Integrate the data from the heterogeneous databases and data sources • Challenges: Common data model, Mappings between data models, Schema integration, Semantic heterogeneity, Handling heterogeneous query models, transaction strategies, security policies, etc. • Information Integration • Integrate heterogeneous information sources • Knowledge integration • Integrate heterogeneous knowledge sources

21. Coalition Application Testbed: A Suggestion • Identify Coalition • Identify Coalition Example: A good starting point will be the Coalition experiments conduced under DARPA;s CoABS program that includes MBP (Master Battle Planner) and CAMPS (Consolidated Air Mobility Planning System) applications • Develop scenarios and determine the roles are of the coalition partners • Identify information to be accessed/shared and how the semantic web may be used by the coalition • Design Policies • Design policies (e.g., security, privacy, trust) for the coalition when accessing information resources • Implement Test Bed • Develop a test bed that uses ontologies for information integration and enforces the policies

22. Vision for Dependable Semantic Web Core Semantic Web Technologies: Systems, Networks, Agents, AI, Machine Learning, Data Mining, Languages, Software Engineering, Information Integration Need research to bring together the above technologies Directions: Security/Trust/Privacy, Integrate sensor technologies, Pervasive computing, Social impact Domain specific semantic webs: DoD, Intelligence, Medical, Treasury,- - - • Some Challenges: Secure Semantic Interoperability; Secure Information Integration; Integrating Pervasive computing and sensors