Dr. Bhavani Thuraisingham

October 1, 2008

Building Trustworthy Semantic Webs

Lecture #11: Logic and Inference RulesSemantic Web Applications

204/20/23 04:07

Outline of the Unit

0 What are logic and inference rules

0 Why do we need rules?

0 Example rules

0 Logic programs

0 Monotonic and Nonmonotoic rules

0 Rule Markup

0 Example Rule Markup in XML

0 Policy Specification

0 Relationship to the Inference and Privacy problems

0 Summary and Directions

0 Part II: Semantic Web Applications

304/20/23 04:07

Logic and Inference

0 First order predicate logic

0 High level language to express knowledge

0 Well understood semantics

0 Logical consequence - inference

0 Proof systems exist

0 Sound and complete

0 OWL is based on a subset of logic – descriptive logic

404/20/23 04:07

Why Rules?

0 RDF is built on XML and OWL is built on RDF

0 We can express subclass relationships in RDF; additional relationships can be expressed in OWL

0 However reasoning power is still limited in OWL

0 Therefore the need for rules and subsequently a markup language for rules so that machines can understand

504/20/23 04:07

Example Rules

0 Studies(X,Y), Lives(X,Z), Loc(Y,U), Loc(Z,U) HomeStudent(X)

0 i.e. if John Studies at UTDallas and John is lives on Campbell Road and the location of Campbell Road and UTDallas are Richardson then John is a Home student

0 Note that

Person (X) Man(X) or Woman(X) is not a rule in predicate logic

That is if X is a person then X is either a man of a woman. This can be expressed in OWL

However we can have a rule of the form

Person(X) and Not Man(X) Woman(X)

604/20/23 04:07

Monotonic Rules

0 Mother(X,Y)

0 Mother(X,Y) Parent(X,Y)

If Mary is the mother of John, then Mary is the parent of John

Syntax: Facts and Rules

Rule is of the form:

B1, B2, ---- Bn A

That is, if B1, B2, ---Bn hold then A holds

704/20/23 04:07

Logic Programming

0 Deductive logic programming is in general based on deduction

- i.e., Deduce data from existing data and rules

- e.g., Father of a father is a grandfather, John is the father of Peter and Peter is the father of James and therefore John is the grandfather of James

0 Inductive logic programming deduces rules from the data

- e.g., John is the father of Peter, Peter is the father of James, John is the grandfather of James, James is the father of Robert, Peter is the grandfather of Robert

- From the above data, deduce that the father of a father is a grandfather

0 Popular in Europe and Japan

804/20/23 04:07

Nonmonotonic Rules

0 If we have X and NOT X, we do not treat them as inconsistent as in the case of monotonic reasoning.

0 For example, consider the example of an apartment that is acceptable to John. That is, in general John is prepared to rent an apartment unless the apartment ahs less than two bedrooms, is does not allow pets etc. This can be expressed as follows:

0 Acceptable(X)

0 Bedroom(X,Y), Y<2 NOT Acceptable(X)

0 NOT Pets(X) NOT Acceptable(X)

0 Note that there could be a contradiction. But with nonmotonic reasoning this is allowed.

904/20/23 04:07

Rule Markup

0 The various components of logic are expressed in the Rule Markup Language – RuleML

0 Both monotonic and nonmonotnic rules can be represented

0 Example representation of Fact P(a) - a is a parent

<fact>

<atom>

<predicate>p</predicate>

<term>

<const>a</const>

<term>

<atom>

</fact>

1004/20/23 04:07

Policies in RuleML

<fact><atom>

<predicate>p</predicate> <term> <const>a</const> <term> <atom>Level = L </fact>

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Example Policies

0 Temporal Access Control

- After 1/1/05, only doctors have access to medical records

0 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?

0 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?

1204/20/23 04:07

Privacy Policies

0 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

0 Augment a database system with a privacy controller for constraint processing

1304/20/23 04:07

System Architecture for Access Control

UserPull/Query Push/result

RuleML DataDocuments

RuleML-Access

RuleMF-Admin Admin

Tools

Policybase

Credentialbase

1404/20/23 04:07

RuleML Data Management

0 Data is presented as RuleML documents0 Query language – Logic programming based?0 Policies in RuleML0 Reasoning engine

- Use the one developed for RuleML

1504/20/23 04:07

Inference/Privacy Control

Policies

Ontologies

Rules

Rule-based Data Management

Rules Data

Inference Engine/Rules Processor

Interface to the Semantic WebTechnologyBy UTD

1604/20/23 04:07

Summary and Directions

0 Rules have expressive and reasoning power 0 Handles some of the inadequacies of OWL0 Both monotonic and nonromantic reasoning0 Logic programming based0 Policies specified in RulesML0 Need to build an integrated system 0 Other rules: SWRL (semantic web rules language)

1704/20/23 04:07

Semantic Web Applications0 Discussion of applications

- Horizontal Information Products at Elsevier

- Data integration at Audi

- Skill finding at Swiss Life

- Think Tank Portal at EnterSearch

- E-Learning

- Web Services

- Multimedia Collection at Scotland Yard

- Online Procurement at Daimler Chrysler

- Device Interoperability at Nokia

0 Common threads and challenges

1804/20/23 04:07

Types of Application

0 Horizontal Information Products at Elsevier: Integration

0 Data integration at Audi: Integration

0 Skill finding at Swiss Life: Search

0 Think Tank Portal at EnterSearch: Knowledge man agent

0 E-Learning: Knowledge management

0 Web Services: Web services (for any of the other applications discussed)

0 Multimedia Collection at Scotland Yard: Searching

0 Online Procurement at Daimler Chrysler: E-Business

0 Device Interoperability at Nokia: Interoperability

1904/20/23 04:07

Horizontal Information Products at Elsevier

0 Elsevier is publishing company based in Amsterdam

- E.g., publisher of Computer Standards and Interface Journal that has papers on all kinds of computer related standards

0 Currently the journals and books are grouped by topics such as say operating systems, databases, etc. (or at a higher level, Biology, Chemistry, etc.)

0 Where do we then put the journal Computer Standards and Interfaces?

0 Need horizontal groupings also

2004/20/23 04:07

Horizontal Information Products at Elsevier

0 Semantic web technologies are being used by Elsevier

- RDF for document representation

- RDF for ontologies

- Query language based on RDF to query the documents and the ontologies

- E.g. Life Science Thesaurus EMTREE

- Other publishing companies are following in Elsevier’s direction

2104/20/23 04:07

Data Integration at Audi

0 Integrate the data in multiple data sources to provide better customer relationship management and other services to improve profits

0 The databases are disparate and heterogeneous

0 Many current operations are carried out manually

0 Expensive and missed opportunities

2204/20/23 04:07

Data Integration at Audi

0 Ontolotues are being specified to address semantic heterogeneous

0 E.g., SLR is a type of camera; one applications calls it SLR, another application calls it Olympus-OM-10

0 When the latter application encounters the term SLR, it will query the ontology and determine that SLR is a camera

0 Details are given in Chapter 6

2304/20/23 04:07

Skill Finding at Swiss Life

0 Swiss Life is an insurance company that developed a system to find all the skills in the company

- E.g., John’s skills are on data management, ontology management

0 Challenging problem as people have multiple skills for different applications

0 Need the following capabilities

- Cross listing of skills

- Querying skills

- - - - -

2404/20/23 04:07

Skill Finding at Swiss Life

0 Ontologies are being developed to specify the skills and query languages to query the ontologies

0 E.g.

<owl: Class rdf: ID = “Publishing”>

<rdfs: subClassOf rdf: resource = ‘#Skills”/>

</owl: Class>

<owl: Class rdf: ID = “Skills”>

- - - -

- </owl: Class>

2504/20/23 04:07

Think Tank Portal at EnterSearch

0 EnterSearch is a consortium of corporations in Europe that provide IT for the energy companies

0 Similar to MCC in Austin TX

0 EnterSerach Portal currently describes the various research projects, papers etc.

0 XML representation is used for describing the web content

0 Need to represent semantics so that the corporations can get answers to useful questions of the form

- “where do I put my computing resources to solve a problem?”

2604/20/23 04:07

Think Tank Portal at EnterSearch

0 Semantic web technologies are being utilized – in particular ontoogies are developed for the following

- Hardware

- Software

- Communications

- E-Commerce

- Agents

- Market/Auction

- Resource Allocation

- - - - -

2704/20/23 04:07

E-Learning

0 With the Internet and the web, we now have on-line universities, course offerings, tutoring etc.

0 Students should have the choice for selecting various courses in the order they want, provide they take the prerequisites

0 Semantic web technologies enable flexible access as well as integration of various data sources and processes to enable learning

0 Ontologies are being developed for learning applications

- E.g., Contents of the courses

- Description of the courses etc.

2804/20/23 04:07

Web Services

0 Web services can be utilized by any of the other applications discussed in this unit (e.g., Elsevier, Audi etc.)

0 We services are invoked to carry out functions on the web including find locations, search for documents etc.

0 Simple services and compound services

0 Three components to the service

- Service profile: Description of the service – what it does

- Serviced model: how it does it

- Service groundings: protocol for invoking the service

2904/20/23 04:07

Web Services

0 DAML and DAML-S developed by the DARPA community combined with the European community developing OIL focused on ,languages for web services

- Semantic of the web services (e.g., reasoning about the services, why certain actions are taken etc.)

- DAML+OIL

0 W3C community started with DAML+OIL for ontology specifications and developed OWL

0 E.g.,

<profile: ServiceProvider rdf ID = “Sportsnews”>

- - - - -

- </profile: ServiceProvider>

3004/20/23 04:07

Multimedia Collection Indexing at Scotland Yard

0 Scotland Yard uses a database to keep track of the antiques that are stolen

0 While sophisticated indexing techniques have been developed, there is a problem with semantics

0 E.g., Red cushioned chair could also be described as Queen Anne chair

0 Ontologies for describing semantics

0 Need more details of the project

3104/20/23 04:07

On-line Procurement at Daimler Chrysler

0 Daimler Chrysler interacts with numerous suppliers to develop a product

0 Standards developed by Rosetta.Net for E-Business are being used for interoperability

- XML syntax, no semantics of the product descriptions are available

0 Ontologies for describing the various product descriptions including the semantics are the long term goal for seamless integration of the supply chain operation

0 Need more details of the project

3204/20/23 04:07

Device Interoperability at Nokia

0 Nokia’s objective is to integrate multiple devices (cell phone, PDA, cars, laptop etc) to provide a pervasive computing environment

0 Objects is to locate the various services and understand the different devices and their functions

- Need to describe the various services

- Current technology provides syntactic descriptions

0 Semantic web technologies, through ontologies enable the understanding the devices and reasons about their functions

0 Need more details of the project

3304/20/23 04:07

Common Threads and Challenges

0 Common Threads

- Building Ontologies for Semantics

- XML for Syntax

0 Challenges

- Scalability, Resolvability

- Security policy specification, Securing the documents and ontologies

- Developing applications for secure semantic web technologies

- Automated tools for ontology management

=Creating, maintaining, evolving and querying ontologies