Semantic Web Fred Automated Goal Resolution on the Semantic Web

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Semantic Web FredAutomated Goal Resolution on
the Semantic Web

• Michael Stollberg
• 38th Hawaiian International Conference on System
  Science
• Hawaii Big Island, 04 January 2005

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Motivation

• Promises of the Semantic Web
• semantically enhanced web content processing
• turn Web into environment for distributed
  computation
• automated collaboration of entities over the
  Internet
• Identified Key Technologies
• Ontologies semantic terminology definitions
• Web Services computational facilities accessible
  over Web
• Agents electronic representatives acting on
  behalf of owner
• Facilitate Automated Collaboration on the
  Semantic Web gt Questions
• What are the building blocks and their functional
  interplay?
• How to determine appropriate collaboration
  partners and resources?
• Which techniques allow efficient high-quality
  collaboration support?

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SWF Objectives / Outline

• Framework for Automated Collaboration
• collaboration model
• building blocks identification
• system components
• Building Blocks Specification
• Freds (agents), Ontologies, Goals, Services,
  Mediators
• structure, usage, and interplay
• semantic resource description
• Cooperation Establishment
• dynamic cooperation establishment
• approach techniques for discovery and
  compatibility determination
• components realization

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Collaboration Model
A Buyer
A Seller
achieve a purchase
cooperation / interaction needed
to be achieved
to be achieved
needed for execution
needed for execution
Objective buy a chair
Objective sell my product
needs to be compatible
needs to be interoperable
Facility
Facility
product search, provide PO, receive payment,
deliver product
select product, accept PO, provide payment,
receive product

• every entity has objectives and facilities
  (symmetric partners)
• cooperation only if profitable for each party

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Mapping to Technology Building Blocks
Fred B
Fred A
Domain Knowledge
representative static
Mediator OO
Ontology
representative static
task delegation
task delegation
collaboration partners compatible goals
Goal
Goal
Mediator GG
usable
usable
assignment / usage dynamic
assignment / usage dynamic
Mediator WG
Mediator WG
collaboration execution interaction of
interoperable services
Mediator WW

• ontology-based knowledge and semantic resource
  descriptions
• dynamic goal assignment service usage
• collaboration if compatible goals interoperable
  services
• collaboration execution service interaction

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System Components
detects new created goals
Goal Detector
for each goal
for each goal
Service Discovery (GS Discoverer)
discoverers possibly usable services
detects potential cooperation partners
Partner Discovery (GG Discoverer)
for possible cooperations
Cooperation Establishment
determines service compatibility for possible
service combinations
Service Compatibility Determination (WW
Discoverer)
Cooperation Contract (F1 (G, S), F1 (G, S), )
Cooperation Execution
execution facilities for service types
execution control / monitoring
Cooperation Execution Environment (Meeting Room)
monitors goal resolution status of participating
Freds
Goal Solver
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Freds
representative static
assignment / usage dynamic

• electronic representative of entities involved in
  service usage provision
• cooperative interface agent
• not (pro / re) active central system control

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Web Service Modeling Ontology WSMO Top Level
Notions
Objectives that a client may have when consulting
a Web Service
Provide the formally specified terminology of the
information used by all other components

• Semantic description of Web Services
• Capability (functional)
• Choreography (interaction)
• Orchestration (composition)

Connectors between components with mediation
facilities for handling heterogeneities

• SWF uses WSMO version 1.0 (www.wsmo.org)

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WSMO elements in SWF

• Ontologies
• semantic terminology definitions used in all
  other element descriptions
• Goals
• tasks delegated to Freds for automated resolution
  
• Goal Templates and Goal Instances
• main description notions submission,
  postcondition, effect
• Services
• computational facilities
• SWF service types
• description notions non-functional properties,
  Capability, Choreography
• Mediators
• connectors with mediation facilities for
  resolving heterogeneities
• mediator types
• source target, mediation service

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Dynamic Collaboration Establishment
Goal Instance
Goal Detector
GI
GI
GG Discoverer
GS Discoverer
GI
S
U
S
WW Discoverer
boolean
Cooperation Contract
(F1 (G1, S1), F2 (G2, S2), )
Cooperation Execution
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Partner Service Discovery

• Action and Object Knowledge Distinction
• Action defines what is to be done
• interacting entities need to have compatible
  actions
• Action-Resource Ontology
• Object defines whereon a action is to be
  performed
• interacting entities need not-contradicting
  object definitions
• gt Set Theoretic Object Matchmaking
• set-based resource descriptions
• matchmaking notions
• realization in VAMPIRE (theorem prover)
• Combination is needed
• (2 resources might have not contradicting objects
  but not-compatible actions)

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Components Architecture

• Design Principles
• modular components (according to discovery
  facility)
• layered architecture
• set-up time runtime discovery
• least expensive operations first
• effective search space narrowing
• GG Discoverer (Partner Discovery)
• matches Goal Instances (active objectives
  assigned to Freds)
• returns sets of Goal Instances (potential
  cooperation partners)
• GS Discoverer (Service Discovery)
• matches Goal Instance and Service Capabilities
• returns set of Services (usable for cooperation
  execution by Goal Instance owner)

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Choreography and Service Compatibility
Fred A (Partner 1)
Fred B (Partner 2)
Potential Coop. Partners (after GG GS
Discovery)
Choreography
Service Interaction Interface
Service Interaction Interface

• Choreography
• agreed valid conversation protocol
• Service Compatibility is a pre-requisite for
  valid conversation protocol
• all information to be exchanged are compatible
• message exchange order allows deadlock-free
  terminating interaction

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Service Compatibility with ASMs
Choreography as Distribted ASM with Services and
their interaction behavior models

• Service Interaction Interface
• as Sequential ASM
• States
• State Signature
• Guarded Transitions

• Service Compatibility Determination
• Information Compatibility
• service descriptions use same / interoperable
  ontologies
• message content is compatible (Object
  Matchmaking)
• direction of messages is inverse / compatible
• Communication Compatibility
• Choreography (i.e. composed global conversation
  protocol) is weak sound
• start and termination state, deadlock-free,
  terminating without additional input

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Aspects for Discussion

• Collaboration Agents and Semantic Web Services
• Freds Collaboration Model
• WSMO
• Goals and Services
• Discovery Realization
• Service Compatibility Determination

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SWF Goals
Goal Template templates for desires to be
delegated to Freds nonFunctionalProperties
importOntologies usedMediators
postConditions effects
Goal Instance concrete desires (instantiated Goal
Templates) assigned to a Fred for automated
resolution instanceOf (goalTemplate)
nonFunctionalProperties (WSMO-nfp
constraints on time, resources, goalResolution)
owner (Fred) submission (instances)
postConditions effects status (resolution
status)
instantiates
refinement only

• WSMO Goal
• pre-defined
• action-resource ontology

• extended WSMO 1.0 Goal definition
• Goal Instance Creation / Task Assignment to Freds
  
• by user via SWF user interface
• dynamically during cooperation establishment

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WSMO Web Service Description

• complete item description
• quality aspects
• Web Service Management

• Advertising of Web Service
• Support for WS Discovery

Capability functional description
Non-functional Properties Core WS-specific

• Realization of WS by using
• other Web Services
• Functional
• decomposition
• WS
• Composition

Web Service Implementation (not of interest in
Web Service Description)

• Interaction Interface
• for consuming WS
• Messages
• External Visible
• Behavior
• Grounding

Choreography --- Interfaces ---
Orchestration
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SWF Service Model

• SWF Service Types
• Plans internal service implemented in Java
• Process multiple-step / nested service
• external Web Services (invoked via WSDL
  description)

Services a computational resource available in
the system, described as WSMO Web Services
nonFunctionalProperties ofType nonFunctionalProper
ties importOntologies ofTypeSet ontology
usedMediators ofTypeSet ooMediator, wgMediator
capability ofType capability
preconditions ofTypeSet axiom assumptions
ofTypeSet axiom postconditions ofTypeSet
axiom effects ofTypeSet axiom
choreography ofType choreography

• 1 common service description language
• Orchestration not of interest

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Mediation

• Heterogeneity
• Mismatches on structural / semantic / conceptual
  / level
• Occur between different components that shall
  interoperate
• Especially in distributed open environments
  like the Internet
• Concept of Mediation (Wiederhold, 94)
• Mediators as components that resolve mismatches
• Declarative Approach
• Semantic description of resources
• Intelligent mechanisms that resolve mismatches
  independent of content
• Mediation cannot be fully automated (integration
  decision)
• Levels of Mediation within Semantic Web Services
  (WSMF)
• Data Level mediate heterogeneous Data Sources
  
• Protocol Level mediate heterogeneous
  Communication Patterns
• Process Level mediate heterogeneous Business
  Processes

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WSMO Mediators Overview
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Mediator Structure
WSMO Mediator uses a Mediation Service via
Source Component
Target Component
1
1 .. n
Source Component

• as a Goal
• directly
• optionally incl. Mediation

Mediation Services
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Action-Resource Ontology

• concept action
• compatibleAction ofType set action
• concept buy subConceptOf action
• compatibleAction ofType set sell
• concept sell subConceptOf action
• compatibleAction ofType set buy
• concept resource
• hasAction ofType set action
• concept goal subConceptOf resource
• concept service subConceptOf resource
• concept buyergoal subConceptOf goal
• hasAction ofType set buy
• concept sellerservice subConceptOf service
• hasAction ofType set sell

Action Taxonomy
Resource Taxonomy
all resources are defined as instances of
resource types
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Set-Based Resource Descriptions
Information Space all possible instances of
used ontologies
Description Notion all possible instances that
satisfy restricted information space

• Goal Instance Postcondition
• Objective receive a purchase contract
• for a wooden chair for Michael Stollberg,
• payment with credit card
• meta-varibale X (dynamically quantified
• by matchmaking notion)
• restrictions on several ontology notions
• WSML syntax

postcondition definedBy
exists ?PurchaseItem(?PurchaseItem item
hasValue ?PurchaseFurniture memberOf
swfmoproduct) and exists
?PurchaseFurniture(?PurchaseFurniture
material hasValues wood,
memberOf furnchair) and
?X purchaseItem hasValue ?PurchaseItem,
buyer hasValue kbMichaelStollberg,
purchasePayment hasValue
kbMSCreditCard memberOf
swfmopurchaseContract .
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Set Theoretic Matchmaking Notions

• Exact Match
• RQ, RR, O, M ?x. (RQ ltgt RR)
• PlugIn Match
• RQ, RR, O, M ?x. (RQ gt RR)
• Subsumption Match
• RQ, RR, O, M ?x. (RQ lt RR)
• Intersection Match
• RQ, RR, O, M ?x. (RQ ? RR)
• Non Match
• RQ, RR, O, M ?x. (RQ ? RR)

RQ
RR
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Partner Discovery (GG Discoverer)
Discovery Request initiating Goal Instance
Discovery Result sets of compatible Goal Instances
(2) GG Matcher
GIg
GIg
GIi
instanceOf, status open
Action-Resource Ontology
instanceOf
(1) Cooperation Knowledge Filter
GTi
GTg
Action Compatibility
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Service Discovery(GS Discoverer)
Action Equality
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Service Compatibility Determination(WW
Discoverer)
under construction