Download - Dr. Bhavani Thuraisingham
Dr. Bhavani Thuraisingham
August 2006
Building Trustworthy Semantic Webs
Unit #1: Introduction to The Semantic Web
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Objective of the Unit
0 This unit will provide an overview of the semantic web and discuss the information management technologies for the semantic web
0 Reference: XML, Databases and the Semantic Web, CRC Press, Thuraisingham, March 2002
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Outline of the Unit
0 Semantic Web Overview
0 Web Data Management and Web Services
0 XML (eXtensible Markup Language)
0 RDF (Resource Description Framework)
0 Information Integration and Ontologies
0 Rules Processing
0 Coalition Testbed Suggestion
0 Directions
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Semantic Web: Overview
0 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
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Layered Architecture for Dependable Semantic Web
0 Some Challenges: Interoperability between Layers; Security and Privacy cut across all layers; Integration of Services; Composability
XML, XML Schemas
Rules/Query
Logic, Proof and TrustTRUST
OtherServicesRDF, Ontologies
URI, UNICODE
PRIVACY
0Adapted from Tim Berners Lee’s description of the Semantic Web
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Relationships between Dependability, Confidentiality, Privacy, Trust
Dependability
ConfidentialityPrivacy
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
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What is XML all about?
0 XML is needed due to the limitations of HTML and complexities of SGML
0 It is an extensible markup language specified by the W3C (World Wide Web Consortium)
0 Designed to make the interchange of structured documents over the Internet easier
0 Key to XML is Document Type Definitions (DTDs)- Defines the role of each element of text in a formal model
0 Allows users to bring multiple files together to form compound documents
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Example XML Document
Patents
Funds
Year: 2002
Name: U. Of X
ExpensesName:CS
titleAuthorID
Asset report
Assets
Dept
Equipment
news
Patent
Other assets
Grants
Contracts
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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>
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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
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RDF
0 Resource Description Framework is the essence of the semantic web
0 Adds semantics with the use of ontologies, XML syntax0 RDF Concepts
- Basic Model =Resources, Properties and Statements
- Container Model=Bag, Sequence and Alternative
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Ontology Mappings
0 Common definitions for any entity, person or thing
0 Several ontologies have been defined and available for use
0 Defining common ontology for an entity is a challenge
0 Mappings have to be developed for multiple ontologies
0 Specific languages have been developed for ontologies including RDF and OIL (Ontology Interface Language)
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Rules Processing
User Interface Manager
ConstraintManager
Rules/ Constraints
Query Processor:
Constraints during query and release operations
Update Processor:
Constraints during update operation
XML Database Design Tool
Constraints during database design operation
XMLDatabase
XML DocumentManager
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Rule-Processing (Concluded)
Policies
Ontologies
Rules
Semantic Web Engine
XML, RDF DocumentsWeb Pages, Databases
Inference Engine/Rules Processor
Interface to the Semantic WebTechnologyBy W3C
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Semantic Web Database Management0 Database access through the semantic web
- XML, RDF technologies
0 Query, indexing and transaction management for web databases
- E.g., New kinds of transaction models for E-commerce applications
- Index strategies for unstructured data
0 Query languages and data models- XML has become the standard document interchange language
0 Managing XML/RDF databases on the web- XML-QL, Extensions to XML, Query and Indexing strategies
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Web Services
0 Web Services are about services on the web for carrying out many functions including directory management, source location, subscribe and publish, etc.
0 Web services description language (WSDL) exists for web services specification
0 Web services architectures have been developed
0 Challenge now is to compose web services; how do you integrate multiple web services and provide composed web service in a seamless fashion
0 Ultimate goal is to have web services for information integration
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Web service architecture
Service requestor
Service providers
UDDI
PublishQuery
Answer
Request the service
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Secure Web Service Architecture
Confidentiality, Authenticity, IntegrityConfidentiality, Authenticity, Integrity
Service requestor
Service provider
UDDIQuery
BusinessEntity
BusinessService
BindingTemplate
<dsig:Signature>
BusinessService
tModel
PublisherAssertion
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Example Web Service
0 Publish/Subscribe Service
Broker/Matching Service
PublisherService: Findingthe Best Route
PublisherService:MaintainingSchedules
Subscription:Request the BestRoute
Subscription:RequestSchedules
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Information Integration
0 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.
0 Information Integration
- Integrate heterogeneous information sources
0 Knowledge integration
- Integrate heterogeneous knowledge sources
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Coalition Application Testbed: A Suggestion
0 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
0 Design Policies
- Design policies (e.g., security, privacy, trust) for the coalition when accessing information resources
0 Implement Test Bed
- Develop a test bed that uses ontologies for information integration and enforces the policies
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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,- - -
0 Some Challenges: Secure Semantic Interoperability; Secure Information Integration; Integrating Pervasive computing and sensors