Dr. Bhavani Thuraisingham

January 2010

Building Trustworthy Semantic Webs

Lecture #3: 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 Overview0 Web Data Management and Web Services0 XML (eXtensible Markup Language)0 RDF (Resource Description Framework)0 Information Integration and Ontologies0 Rules Processing0 Coalition Testbed Suggestion0 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, RulesApplications: 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 Other

ServicesRDF, 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

newsPatent

Other assets

GrantsContracts

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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 thing0 Several ontologies have been defined and available for use0 Defining common ontology for an entity is a challenge0 Mappings have to be developed for multiple ontologies0 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 technologies0 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 developed0 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

UDDIPublish

Query

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 Suggestion0 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 coalition0 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 WebCore Semantic Web Technologies:Systems, Networks, Agents, AI, Machine Learning, Data Mining, Languages, Software Engineering, Information IntegrationNeed 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