Logic Foundation and Services for Semantic Web

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Logic Foundation and Services for Semantic Web
Zhongzhi Shi shizz_at_ics.ict.ac.cn Institute of
Computing Technology Chinese Academy of Scicence
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Outline

• Introduction
• Description Logic
• Dynamic Description Logic
• Agent-based Services
• Ontology-based Knowledge Management KMSphere
• Conclusions

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Semantic Web

• Web was invented by Tim Berners-Lee (amongst
  others), a physicist working at CERN
• His vision of the Web was much more ambitious
  than the reality of the existing (syntactic) Web

a plan for achieving a set of connected
applications for data on the Web in such a way as
to form a consistent logical web of data
an extension of the current web in which
information is given well-defined meaning, better
enabling computers and people to work in
cooperation
This vision of the Web has become known as the
Semantic Web
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Semantics Is Important

• Avoid transformation code between data sets
• Unambiguously capture service profiles
• Enable dynamic discovery of services
• Use reasoners to locate services in yellow
  pages
• Enable dynamic collaboration of services
• Use reasoners to infer service descriptions and
  capabilities
• Enable rich, automatic, service orchestration
• Process layer will be far more automated with
  semantics

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Adding Semantic Markup
Make web resources more accessible to automated
processes by

• Extend existing rendering markup with semantic
  markup
• Metadata annotations that describe
  content/function of web accessible resources
• Useing Ontologies to provide vocabulary for
  annotations
• Formal specification is accessible to machines
• Semantics given by ontologies

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Ontology

• In philosophy, an ontology is a theory about the
  nature of existence.
• An ontology is a document or file that formally
  defines the relations among terms.
• An ontology is a formal, explicit specification
  of a shared conceptualization.
• The most typical kind of ontology for the Web has
  a taxonomy and a set of inference rules.

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Ontologies

• XML DTDs
• Document Type Definition
• Define structure Car application contains a
  price (integer), description and colour

• XML Schemas
• Allows richer definitions
• Define structure Car application contains a
  price (ve integer between 1 and 20,000),
  description and colour (taken from fixed
  vocabulary)

• Ontologies
• Define relationships relationship between, say,
  a postcode, a town, a suburb, etc
• Builds on AI techniques

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The Semantic Web layer cake by Tim Berners-Lee
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Web Ontology Language

• The W3C Web Ontology Working Group (WebOnt) is
  tasked with producing a web ontology language
  extending the reach of XML, RDF, and RDF Schema.
  This language, called OWL, is based on the
  DAMLOIL web ontology language.

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The Ontology Language Stack
OWL
DAML-S
DAML-R
DAMLOIL
OIL
DAML-Ont
DC
PICS
RDF Schema
RDF
XOL
HTML
XML Name Space XML Schema
Unicode
URI
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OWL

• Loose-coupling semantics may be decoupled from
  the application code (or parsing algorithms)
• Machine-actionable automated decisions can be
  made from interpretable inferences
• Highly expressive can capture core elements of
  EER, UML, and frame-based systems
• Precision language checking available to
  prevent inconsistent/contradictory model
  semantics

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Outline

• Introduction
• Description Logic
• Dynamic Description Logic
• Agent-based Services
• Ontology-based Knowledge Management KMSphere
• Conclusions

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Description Logics

• Consistency query results, across vendor
  implementations and instances, should be
  consistent
• Performance Although performance metrics depend
  on model constructs, OWL-DL supports highly
  optimized inference algorithms
• Predictable semantics are mathematically
  decidable within the model, reasoning is finite
• Foundational provides a baseline inside
  applications for layered semantic models
• Reliability if the answer to a query is implied
  by any of the model data, it will be found
  guaranteed.

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Description Logic

• Frame-based system
• Semantic Network
• Object-oriented representation
• Semantic data models
• Ontology language

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Description Logic

• Concepts and Role
• TboxAssertions
• AboxInstance
• Reasoning mechanism in terms of Tbox and Abox

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TBox
TBox Language Set of axioms
Definition Concept name A C, A ? C Father
Man ? ? has-child.Human Human ? Animal ? Biped
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TBox Instance
? Concept entity (one unit predicate,class) Exam
pleStudent, Married x Student(x)
,x Married(x) Bird ? Animal, Man ? Human
? Roles Property (two unit predicate,role) Examp
lesFriend,Loves ltx,ygt Friend(x,y) ,ltx,ygt
Loves(x,y)
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ABox Language(Assertion)
Set of concrete axioms
? Concept assertion aC ExamplesTom is a
student Tom Student Or Student(Tom) John
Man ? ? has-child.Female
? Role assertion Indicate the role between two
objects lta,bgtR ExampleJohn has a child called
Mary ltJohn, Marygt has-child
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Syntax and Semantics
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OWL Class Constructors
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OWL Axioms
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Reasoning in DL

• 1) Subsumption
• 2) consistency
• 3) satisfiability
• 4) instance checking

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K B
TBox(Scheme) Man Human ? Male Happy-father
Human ? ? Has-child.Female?
Abox(Data) John Happy-father ltJohn,Marygt
Has-child
Reasoning
Interface
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Outline

• Introduction
• Description Logic
• Dynamic Description Logic
• Agent-based Services
• Ontology-based Knowledge Management KMSphere
• Conclusions

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Dynamic Description Logic

• The primitive symbols
• Concept nameC1, C2,
• Role nameR1, R2,
• Individual constanta, b, c,
• Individual variablex, y, z,
• Concept operation?, ?, ?, ?, ?
• Axiom operation?, ?, ??
• ActionA1, A2,
• Action constraction(composition),?
  (alternation), (repeat),?(test)
• Action variablea,ß,
• Axiom variable?, ?, p,
• State variableu, v, w,

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Dynamic Description Logic

• Concepts in DDL are defined as the following
• (1) Primitive concept P, top ? and bottom ? are
  concepts.
• (2) ?C, C?D, C?D are concepts.
• (3) ?R.C, ?R.C are concepts.

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Dynamic Description Logic
An action description is the form of
where (1) A is the action name. (2) x1, , xn
are individual variables, which denote the
objects the action operate on. (3) PA is the set
of preconditions, which must be satisfied before
the action is executed. (4) EA is the set of
results, which denote the effects of the action.
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DDL Semantics

• Actions in DDL are defined as the following
• Atom action A(a1, , an) is action.
• If a and ß are actions, then aß, a?ß, a are
  actions
• If ? is an assertion formula, then ? ? is
  action.

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Outline

• Introduction
• Description Logic
• Dynamic Description Logic
• Agent-based Services
• Ontology-based Knowledge Management KMSphere
• Conclusions

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What is a Semantic WS
An ontology to describe Web-services
OWL-S
What a service does? (Discovery)
How the service works? (Composition)
How the service is implemented? (Invocation)
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Composition of Services

• Planning based approaches
• construct a plan from elementary services to
  obtain a required functionality.
• reasoning based only on component specifications
• plan built every time from scratch
• Knowledge based approaches
• re-use preconfigured templates
• reasoning with specialised knowledge in a narrow
  domain
• sophisticated domain knowledge is needed

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Web Services Composition
OWL-S
semantics
Commitment Protocols
CTR-S
?-Calc
WSCL
Mealy
BPML
Complexity of glue language
Roman
CSP
WSDL
Complexity of component services
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OWL-S
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OWL-S Context
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Service Description Language SDLSIN

• ltasdl-descrgt(ctype
• service-name name
• context context-name
• types (type-name ltmodifiergt
  type)
• isa name
• inputs (variable ltmodifiergt
  put-type-name)
• outputs (variable ltmodifiergt
  put-type-name)
• input-constraints
  (constraint)
• output-constrains
  (constraint)
• io-constrains (constraint)
• concept-description
  (ontology-name ontology-body)
• state-language name
• concept-language name
• attributes (attributes-name
  attributes-value)
• text-description name
• )

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OWL-S
OWL-S Interpreter
DDL
Incidences matrixDDL
OWL-S
Petri Net Generator
Petri Net Analysor
Services
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Agent-based Services
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Architecture of Agent
Components
Belief Update
Knowledge base
Action Descriptions
Axioms
Current Belief
Belief Update
Planner
Scheduler
Sensor
Decision Maker
Goal rules
Plan rules
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Metal State Model

• Mental State ltK, A, G, P, I gt,
• Where
• K belief
• A action
• G goal
• P plan
• I intention?

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Outline

• Introduction
• Description Logic
• Dynamic Description Logic
• Agent-based Services
• Ontology-based Knowledge Management KMSphere
• Conclusions

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Ontology Development
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KMSphere
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KMSphere
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KMSphere
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KMSphere
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KMSphere Demo
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KMSphere Demo
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KMSphere Demo
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KMSphere Demo
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KMSphere Demo
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KMSphere Demo
RDQL (RDF Data Query Language)??
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Agent Grid Intelligence Platform AGrIP
E-B
E-G
IE
DSS
IB
Simul
Corl
Diag.
Information Sourses
Applications
Web
Middelware
GIS
CBR
Databases
GHunt
OKPS
CAD
MSMiner
MIRES
KMSphere
Stream Media
MAGE
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Emergency Interactive Systsem GEIS
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Distributed Data Mining
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Conclusions

• The dynamic description logic is a good logic
  foundation for Semantic Web.
• Semantic Web services in terms of agents
• Ontology-based knowledge management system
  KMSphere provides knowledge sharing to users.

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THANK YOU!
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