Building Trustworthy
Semantic Webs
Unit #1: Introduction to The Semantic Web
Dr. Bhavani Thuraisingham
August 2006
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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
0Adapted from Tim Berners Lee’s description of the Semantic Web
T
R
U
S
T
P
R
I
V
A
C
Y
Logic, Proof and Trust
Rules/Query
RDF, Ontologies
Other
Services
XML, XML Schemas
URI, UNICODE
0 Some Challenges: Interoperability between Layers; Security and
Privacy cut across all layers; Integration of Services; Composability
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Relationships between Dependability, Confidentiality,
Privacy, Trust
Privacy
Confidentiality
Dependability
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
0
0
0
0
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
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Example XML Document
Year: 2002
Asset report
Assets
Dept
Patents
Name: U. Of X
Equipment
Other assets
Funds
Patent
news
Name:
CS
Expenses
Contracts
Grants
ID Author title
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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 syntax
0 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
Rules/
Constraints
Constraint
Manager
Query Processor:
Constraints during
query and release
operations
Update
Processor:
XML Database
Design Tool
Constraints during
database design
operation
Constraints
during
update
operation
XML Document
Manager
XML
Database
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Rule-Processing (Concluded)
Technology
By W3C
Interface to the Semantic Web
Inference Engine/
Rules Processor
Policies
Ontologies
Rules
Semantic Web
Engine
XML, RDF
Documents
Web Pages,
Databases
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Semantic Web Database Management
0 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
Publish
Query
UDDI
Answer
Service
requestor Request the
service
Service
providers
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Secure Web Service Architecture
Confidentiality, Authenticity, Integrity
BusinessEntity
<dsig:Signature>
tModel
Query
UDDI
BusinessService
PublisherAssertion
BusinessService
Service
requestor
Service
provider
BindingTemplate
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Example Web Service
0 Publish/Subscribe Service
Publisher
Service: Finding
the Best Route
Publisher
Service:
Maintaining
Schedules
Broker/Matching Service
Subscription:
Request the Best
Route
Subscription:
Request
Schedules
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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