Semantic Web Fred Automated Goal Resolution on the Semantic

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					           Semantic Web Fred
Automated Goal Resolution on the Semantic Web

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

                         Semantic Web Fred   HICSS-38                         2
          SWF Objectives / Outline
1. Framework for Automated Collaboration
    -   collaboration model
    -   building blocks identification
    -   system components

2. Building Blocks Specification
    -   Freds (agents), Ontologies, Goals, Services, Mediators
    -   structure, usage, and interplay
    -   semantic resource description

3. Cooperation Establishment
    -   dynamic cooperation establishment
    -   approach & techniques for discovery and compatibility determination
    -   components realization

                          Semantic Web Fred   HICSS-38                        3
                         Collaboration Model
                 A Buyer                                                    A Seller
                                        achieve a purchase
                               cooperation / interaction needed
                          to be                                       to be
needed for                                                           achieved              needed for
 execution               achieved                                                           execution
                 Objective:           needs to be compatible         Objective:
                 “buy a chair”                                       “sell my product”

                                     needs to be interoperable
     Facility:                                                                     Facility:
select product, accept PO, provide                                   product search, provide PO, receive
payment, receive product                                             payment, deliver product



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

                                      Semantic Web Fred   HICSS-38                                  4
      Mapping to Technology: Building Blocks
                        Fred A                                                              Fred B
                                                       Domain Knowledge
                                                                                                       representative
  representative                                                         Mediator
                                                   Ontology                                                static
     static                                                                  OO
                          Owner                                                     Owner
                          task delegation                                           task delegation
                                                   collaboration partners:
                           Goal                                  Mediator            Goal
                                                                    GG

                              usable                   compatible goals                 usable
                                                                                                      assignment / usage
assignment / usage
   dynamic                                                                           Mediator
                                                                                                         dynamic
                           Mediator
                             WG                                                        WG
                                                   collaboration execution:
                                                                  Mediator
                          Service                                   WW
                                                                                    Service
                                            interaction of interoperable services

                   -   ontology-based knowledge and semantic resource descriptions
                   -   dynamic goal assignment & service usage
                   -   collaboration if compatible goals & interoperable services
                   -   collaboration execution = service interaction
                                             Semantic Web Fred   HICSS-38                                        5
                       System Components
                                            Goal Detector            detects new created goals

                 for each goal                                                 for each goal

   detects potential   Partner Discovery                         Service Discovery          discoverers possibly
cooperation partners      (GG Discoverer)                           (GS Discoverer)         usable services
                                       for possible cooperations


Cooperation                 Service Compatibility Determination                       determines service compatibility
Establishment                                  (WW Discoverer)                        for possible service combinations

                                        Cooperation Contract
                                     (F1 (G, {S}), F1 (G, {S}), …)

Cooperation                                                                           execution facilities for service types
                            Cooperation Execution Environment
Execution                                      (Meeting Room)                         & execution control / monitoring


                                                                    monitors goal resolution status
                                               Goal Solver          of participating Freds

                                     Semantic Web Fred   HICSS-38                                                      6
                                            Freds
                                               Social                                           representative
                                     owner, preferences, policies,                                 static
                                                history

                                                       electronic
                                                       representative


          dynamically                              Fred                         service usage
         assigned task

                                                                                                assignment / usage

                      Goal                                              Service                     dynamic
             task delegated to Fred for                           provided services, usage
               automated resolution                              permissions, used services

                                              resolved by




- electronic representative of entities involved in service usage & provision
- cooperative interface agent
- not (pro / re) active: central system control
                               Semantic Web Fred   HICSS-38                                                      7
           Web Service Modeling Ontology
            WSMO – Top Level Notions
                           Objectives that a client may have
                           when consulting a Web Service


Provide the formally                                                 Semantic description of Web
specified terminology                                                Services:
of the information                                                   - Capability (functional)
used by all other                                                    - Choreography (interaction)
components                                                           - Orchestration (composition)



                        Connectors between components with
                        mediation facilities for handling heterogeneities


        SWF uses WSMO version 1.0 (www.wsmo.org)
                                 Semantic Web Fred   HICSS-38                               8
            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

                             Semantic Web Fred   HICSS-38                           9
 Dynamic Collaboration Establishment

Goal Detector                           Goal Instance


                GI                                                      GI
                   GG           {GI}                        {S}      GS
                Discoverer                         U              Discoverer
                                           {S}
                                             WW
                                          Discoverer
                                   boolean

                            Cooperation Contract
                      (F1 (G1, {S}1), F2 (G2, {S}2), …)



                             Cooperation Execution

                             Semantic Web Fred   HICSS-38                      10
           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
       => 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)


                               Semantic Web Fred   HICSS-38                         11
              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)

                              Semantic Web Fred   HICSS-38                            12
Choreography and Service Compatibility
              Fred A (Partner 1)                                                            Fred B (Partner 2)
                                                                 Potential Coop. Partners
                                                                (after GG & GS Discovery)




                                                                                                     Service Interaction Interface
                    Service Interaction Interface




                                                                 Choreography




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
                                                    Semantic Web Fred   HICSS-38                                                     13
           Service Compatibility with ASMs

      Service Interaction Interface                               Choreography
      as Sequential ASM:                                                  as
      - States                                                    Distribted ASM
      - State Signature                                          with Services and
      - Guarded Transitions                                       their interaction
                                                                 behavior models




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

                                  Semantic Web Fred   HICSS-38                        14
          Aspects for Discussion


   Collaboration: Agents and Semantic Web Services
   Freds & Collaboration Model
   WSMO
   Goals and Services
   Discovery Realization
   Service Compatibility Determination


                  Semantic Web Fred   HICSS-38        15
                                    SWF Goals
 Goal Template                                           Goal Instance
 templates for desires to be                             concrete desires (instantiated Goal Templates) assigned to
 delegated to Freds             instantiates             a Fred for automated resolution
  nonFunctionalProperties
  importOntologies                                       instanceOf (goalTemplate)
  usedMediators                                           nonFunctionalProperties (WSMO-nfp +
  postConditions                                           constraints on time, resources, goalResolution)
  effects                                                 owner (Fred)
                               refinement only            submission (instances)
- WSMO Goal                                               postConditions
- pre-defined                                             effects
- action-resource ontology                                status (resolution status)



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

                                   Semantic Web Fred   HICSS-38                                                       16
        WSMO Web Service Description
         - complete item description                            - Advertising of Web Service
         - quality aspects                                      - Support for WS Discovery
         - Web Service Management
       Non-functional Properties                                        Capability

            Core + WS-specific                                    functional description


                                                                                          Realization of
Interaction Interface                                                                     WS by using
for consuming WS                        Web Service                              WS
                                                                                          other Web
- Messages                            Implementation                                      Services
                                                                                 WS
- External Visible                     (not of interest in Web                            - Functional
  Behavior                              Service Description)
                                                                                 WS
                                                                                            decomposition
- ‘Grounding’                                                                             - WS
                                                                                            Composition

                    Choreography --- Interfaces --- Orchestration
                                 Semantic Web Fred   HICSS-38                                        17
                         SWF Service Model
      SWF Service Types
        1.   Plans = internal service implemented in Java
        2.   Process = multiple-step / nested service
        3.   external Web Services (invoked via WSDL description)


Services
a computational resource available in the system, described as WSMO   - 1 common service
Web Services                                                            description language
 nonFunctionalProperties ofType nonFunctionalProperties
 importOntologies ofTypeSet ontology                                  - Orchestration not of
 usedMediators ofTypeSet {ooMediator, wgMediator}                       interest
 capability ofType capability
   preconditions ofTypeSet axiom
   assumptions ofTypeSet axiom
   postconditions ofTypeSet axiom
   effects ofTypeSet axiom
 choreography ofType choreography


                                   Semantic Web Fred   HICSS-38                                18
                               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):
    (1) Data Level:        mediate heterogeneous Data Sources
    (2) Protocol Level:    mediate heterogeneous Communication Patterns
    (3) Process Level:     mediate heterogeneous Business Processes

                            Semantic Web Fred   HICSS-38                             19
WSMO Mediators Overview




      Semantic Web Fred   HICSS-38   20
                Mediator Structure

  Source                     WSMO Mediator
Component
                       uses a Mediation Service via              1     Target
            1 .. n
                                                                     Component
  Source
Component
                                               - as a Goal
                                               - directly
                                               - optionally incl. Mediation



                                    Mediation
                                     Services


                     Semantic Web Fred   HICSS-38                                21
            Action-Resource Ontology
             concept action
               compatibleAction ofType set action
             concept buy subConceptOf action                 Action
               compatibleAction ofType set sell             Taxonomy
             concept sell subConceptOf action
               compatibleAction ofType set buy

             concept resource
               hasAction ofType set action
             concept goal subConceptOf resource
Resource     concept service subConceptOf resource
Taxonomy
             concept buyergoal subConceptOf goal
                hasAction ofType set buy
             concept sellerservice subConceptOf service
                hasAction ofType set sell


           all resources are defined as instances of resource types



                           Semantic Web Fred   HICSS-38                22
      Set-Based Resource Descriptions
  Information Space                                                          Description Notion
 all possible instances                                                  all possible instances that
   of used ontologies                                               satisfy restricted information space


postcondition                                                   Goal Instance Postcondition
 definedBy                                                      - Objective: receive a purchase contract
  exists ?PurchaseItem(?PurchaseItem[                             for a wooden chair for Michael Stollberg,
    item hasValue ?PurchaseFurniture
  ] memberOf swfmo:product) and                                   payment with credit card
  exists ?PurchaseFurniture(?PurchaseFurniture[
    material hasValues {wood},                                  - meta-varibale X (dynamically quantified
  ] memberOf furn:chair) and
 ?X[
                                                                  by matchmaking notion)
   purchaseItem hasValue ?PurchaseItem,
   buyer hasValue kb:MichaelStollberg,                          - restrictions on several ontology notions
   purchasePayment hasValue kb:MSCreditCard
 ] memberOf swfmo:purchaseContract .
                                                                - WSML syntax
                                 Semantic Web Fred   HICSS-38                                       23
Set Theoretic Matchmaking Notions
1. Exact Match:
     RQ, RR, O, M ╞ x. (RQ <=> RR)
2. PlugIn Match:
     RQ, RR, O, M ╞ x. (RQ => RR)
3. Subsumption Match:
     RQ, RR, O, M ╞ x. (RQ <= RR)
4. Intersection Match:
     RQ, RR, O, M ╞ x. (RQ  RR)                       X



5. Non Match:
     RQ, RR, O, M ╞ ¬x. (RQ  RR)

                  Semantic Web Fred   HICSS-38
                                                 = RQ   = RR   24
                   Partner Discovery
                                (GG Discoverer)

  Discovery Request                                               Discovery Result
initiating Goal Instance                                  sets of compatible Goal Instances



                                       (2) GG                    GIg                GIg
          GIi
                                       Matcher

                                                                         instanceOf,
      instanceOf                   Action-Resource                     status = ‘open’
                                       Ontology

                                  (1) Cooperation
         GTi                                                             GTg
                                  Knowledge Filter


                           Action Compatibility


                           Semantic Web Fred   HICSS-38                                       25
                    Service Discovery
                                   (GS Discoverer)



Discovery Request                                                     Discovery Result
                       GIi                        (2) GIS Matcher
   Goal Instance                                                       usable Services


                                                   Discovery Result
                    instanceOf
                                                     (intermediary)




                       GTi                        (1) Pre-Selector



                                  Service              Service           Action
                                 Repository             Filter
                                                                         Equality



                             Semantic Web Fred   HICSS-38                                26
                                                                         under construction

Service Compatibility Determination
                         (WW Discoverer)
                        Discovery Request
                         set of services {S}



                  Choreography Description Translator


             WSDL2StateSign                    BPEL2ASM




     (1) SCinfo Checker                  yes        (2) SCcomm Checker

             no



                        Discovery Result
                   Boolean (service compatibility)




                     Semantic Web Fred   HICSS-38                                     27