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

Semantic Web Fred HICSS-38 2 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 3 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 4 Collaboration Model - every entity has objectives and facilities (symmetric partners) - cooperation only if profitable for each party A BuyerA Seller achieve a purchase cooperation / interaction needed Objective: “buy a chair” Objective: “sell my product” needs to be compatible Facility: needs to be interoperable product search, provide PO, receive payment, deliver product to be achieved select product, accept PO, provide payment, receive product Facility: needed for execution needed for execution to be achieved

Semantic Web Fred HICSS-38 5 Mapping to Technology: Building Blocks -ontology-based knowledge and semantic resource descriptions -dynamic goal assignment & service usage -collaboration if compatible goals & interoperable services -collaboration execution = service interaction collaboration partners: compatible goals Fred B Service Goal Ontology Mediator OO Owner task delegation Mediator WG usable Fred A Service Goal Owner task delegation Mediator GG collaboration execution: interaction of interoperable services Mediator WW Domain Knowledge Mediator WG usable representative static assignment / usage dynamic representative static assignment / usage dynamic

Semantic Web Fred HICSS-38 6 System Components Goal Detector Partner Discovery (GG Discoverer) Service Discovery (GS Discoverer) Service Compatibility Determination (WW Discoverer) Goal Solver detects new created goals discoverers possibly usable services for each goal detects potential cooperation partners for possible cooperations Cooperation Contract (F1 (G, {S}), F1 (G, {S}), …) determines service compatibility for possible service combinations execution facilities for service types & execution control / monitoring monitors goal resolution status of participating Freds Cooperation Execution Environment (Meeting Room) Cooperation Establishment Cooperation Execution

Semantic Web Fred HICSS-38 7 Freds Goal task delegated to Fred for automated resolution Service provided services, usage permissions, used services Social owner, preferences, policies, history Fred electronic representative dynamically assigned task service usage resolved by -electronic representative of entities involved in service usage & provision -cooperative interface agent -not (pro / re) active: central system control assignment / usage dynamic representative static

Semantic Web Fred HICSS-38 8 Web Service Modeling Ontology WSMO – Top Level Notions SWF uses WSMO version 1.0 ( Provide the formally specified terminology of the information used by all other components Semantic description of Web Services: - Capability (functional) - Choreography (interaction) - Orchestration (composition) Objectives that a client may have when consulting a Web Service Connectors between components with mediation facilities for handling heterogeneities

Semantic Web Fred HICSS-38 9 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 Dynamic Collaboration Establishment Goal Instance GG Discoverer GS Discoverer WW Discoverer Cooperation Contract GI {GI} GI {S} boolean {S} U (F 1 (G 1, {S} 1 ), F 2 (G 2, {S} 2 ), …) Goal Detector Cooperation Execution

Semantic Web Fred HICSS 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 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 Choreography and Service Compatibility Fred A (Partner 1)Fred B (Partner 2) Potential Coop. Partners (after GG & GS Discovery) 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 Service Compatibility with ASMs Choreography as Distribted ASM with Services and 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 Service Interaction Interface as Sequential ASM: - States - State Signature - Guarded Transitions

Semantic Web Fred HICSS 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 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) - WSMO Goal - pre-defined - action-resource ontology instantiates refinement only -extended WSMO 1.0 Goal definition -Goal Instance Creation / Task Assignment to Freds oby user via SWF user interface odynamically during cooperation establishment

Semantic Web Fred HICSS WSMO Web Service Description Web Service Implementation (not of interest in Web Service Description) Choreography --- Interfaces --- Capability functional description WS - Advertising of Web Service - Support for WS Discovery Interaction Interface for consuming WS - Messages - External Visible Behavior - ‘Grounding’ Realization of WS by using other Web Services - Functional decomposition - WS Composition Non-functional Properties Core + WS-specific - complete item description - quality aspects - Web Service Management WS Orchestration

Semantic Web Fred HICSS 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 Web Services nonFunctionalProperties ofType nonFunctionalProperties 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

Semantic Web Fred HICSS 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 WSMO Mediators Overview

Semantic Web Fred HICSS Mediator Structure WSMO Mediator uses a Mediation Service via Source Component Source Component Target Component 1.. n 1 Mediation Services - as a Goal - directly - optionally incl. Mediation

Semantic Web Fred HICSS 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

Semantic Web Fred HICSS Set-Based Resource Descriptions Information Space all possible instances of used ontologies Description Notion all possible instances that satisfy restricted information space postcondition definedBy exists ?PurchaseItem(?PurchaseItem[ item hasValue ?PurchaseFurniture ] memberOf swfmo:product) and exists ?PurchaseFurniture(?PurchaseFurniture[ material hasValues {wood}, ] memberOf furn:chair) and ?X[ purchaseItem hasValue ?PurchaseItem, buyer hasValue kb:MichaelStollberg, purchasePayment hasValue kb:MSCreditCard ] memberOf swfmo:purchaseContract. 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

Semantic Web Fred HICSS Set Theoretic Matchmaking Notions 1.Exact Match: R Q, R R, O, M ╞ x. (R Q R R ) 2.PlugIn Match: R Q, R R, O, M ╞ x. (R Q => R R ) 3.Subsumption Match: R Q, R R, O, M ╞ x. (R Q <= R R ) 4.Intersection Match: R Q, R R, O, M ╞ x. (R Q  R R ) 5.Non Match: R Q, R R, O, M ╞ ¬x. (R Q  R R ) = R Q = R R X

Semantic Web Fred HICSS Partner Discovery (GG Discoverer) GI i Action-Resource Ontology Discovery Result sets of compatible Goal Instances (2) GG Matcher Discovery Request initiating Goal Instance GT i (1) Cooperation Knowledge Filter GT g GI g instanceOf instanceOf, status = ‘open’ Action Compatibility

Semantic Web Fred HICSS Service Discovery (GS Discoverer) Discovery Request Goal Instance Discovery Result usable Services Service Repository Discovery Result (intermediary) Service Filter (2) GIS Matcher GI i GT i instanceOf (1) Pre-Selector Action Equality

Semantic Web Fred HICSS Service Compatibility Determination (WW Discoverer) Discovery Request set of services {S} Discovery Result Boolean (service compatibility) (2) SC comm Checker Choreography Description Translator (1) SC info Checker WSDL2StateSignBPEL2ASM yes no under construction