Universität Innsbruck Leopold Franzens  Copyright 2007 DERI Innsbruck Technical Task Fair December 2007 SWS Composition The SUPER Approach Jörg Hoffmann and James Scicluna DERI Innsbruck – University of Innsbruck

Technical Task Fair December 2007 Composition Component Jörg Hoffmann, James Scicluna, Adina Sirbu Focus: –WSC at WSMO capability level –Integration with Ontologies, i.e. first-order theories –Scalability! Trade-off against expressivity Two prototypes under development: –SUPER (James): Restrict ontology to obtain polytime reasoning about service outcome –SemBiz (Adina): Restrict service effects to be able to allow more general ontologies

3 Technical Task Fair December 2007 Talk Outline Conceptual Background (Jörg) –WSC Formalism –Search States –Heuristic Function –TPSA Results Prototype Demo (James) –WSML Models –The Tool in Action

4 Technical Task Fair December 2007 Conceptual Background Universität Innsbruck Leopold Franzens Technical Task Fair  Copyright 2006 DERI Innsbruck SWS Composition – The SUPER Approach December 2007

5 Technical Task Fair December 2007 Talk Outline Conceptual Background (Jörg) –WSC Formalism –Search States –Heuristic Function –TPSA Results Prototype Demo (James) –WSML Models –The Tool in Action

6 Technical Task Fair December 2007 WSC Formalism -- Syntax Ontologies are 1st-order theories  –We actually handle a restricted subset, see later SWS and goals at WSMO capability level: –Precondition, effect are conjunctions of literals –Variables may be shared Precondition variables  „input parameters“ Not-shared effect variables  „output parameters“ SWS call: parameters instantiated with constants –Assumption not considered, postcondition included in effect Assume same ontology for goal + all SWS

7 Technical Task Fair December 2007 WSC Formalism -- Semantics Interpretation I: over finite set of constants –Initially, user input; SWS may create new constants Belief b: set of possible interpretations Initial belief b 0 : all I that satisfy  and goal precondition Outcome of applying w in b: –Defined following [Baader et al, deGiacomo et al] –All I that satisfy  and Eff w and that differ minimally from b –Computationally very hard! E.g. coNP-complete even if  is a Horn theory [Eiter&Gottlob,AI-92] –„Minimal change“: frame problem! E.g. If credit card A is charged then credit card B remains unaffected Composed web service:  w 1,..., w n  so that all I in resulting b satisfy goal effect –Partially ordered solution :iff all serialisations are solutions

8 Technical Task Fair December 2007 Talk Outline Conceptual Background (Jörg) –WSC Formalism –Search States –Heuristic Function –TPSA Results Prototype Demo (James) –WSML Models –The Tool in Action

9 Technical Task Fair December 2007 Search States „Search“ == the process that looks for a suitable composed web service Forward search: start in b 0, apply web services, stop when solution b is found Question: –Which information – search states – do we maintain during search? –How do we maintain it? Trivial answer: search state == belief –Order 2 k if goal precondition leaves k propositions unspecified  bad idea! (actually, this was implemented in ASG...) For scalability, SUPER focus on polytime methods

10 Technical Task Fair December 2007 Search States in SUPER Search state: set L of literals –Those literals that hold in all interpretations of the corresponding belief! –Well we need some add-ons depending on form of  Given L and w, compute new L‘ in polytime –Challenging: minimal change semantics! –E.g. coNP-complete for Horn  Ontology constructs handled: –Subsumption relations, attribute range/image restrictions, relation reflexivity, relation symmetry (actually, any 2-clause) –Attribute cardinality upper bounds –Extends the results of [deGiacomo et al, AAAI-06]; further extensions underway

11 Technical Task Fair December 2007 Talk Outline Conceptual Background (Jörg) –WSC Formalism –Search States –Heuristic Function –TPSA Results Prototype Demo (James) –WSML Models –The Tool in Action

12 Technical Task Fair December 2007 Heuristic Function There are many search states s  one s for every combination of SWS Exploring them all  Business Expert will not be happy Define h: S →  0 (map any s to natural number) –Estimates distance to nearest solution state –Prefer states s with lower h(s) –Weighted A* h(s) computed by solving abstracted WSC task!

13 Technical Task Fair December 2007 Abstracted WSC Act as if both A and  A could be true together –active(b)  cancelled(b) This makes life easier: –Removes frame problem: the new things do not contradict the old things –„Previously it was active, now it‘s also cancelled“ –Abstract WSC solved by a fixpoint operation –„Fixpoint“: no new SWS can be applied Proved to be: –Polytime –Over-approximating („abstract allows all real solutions“)

14 Technical Task Fair December 2007 Talk Outline Conceptual Background (Jörg) –WSC Formalism –Search States –Heuristic Function –TPSA Results Prototype Demo (James) –WSML Models –The Tool in Action

15 Technical Task Fair December 2007 TPSA Results

16 Technical Task Fair December 2007 Prototype Demo Universität Innsbruck Leopold Franzens Technical Task Fair  Copyright 2006 DERI Innsbruck SWS Composition – The SUPER Approach December 2007

17 Technical Task Fair December 2007 Talk Outline Conceptual Background (Jörg) –WSC Formalism –Search States –Heuristic Function –TPSA Results Prototype Demo (James) –WSML Models –The Tool in Action

18 Technical Task Fair December 2007 Current supported constructs in the implementation: –Subsumption Hierarchies –Attribute specifications –Boolean built-ins Translated trivially to Predicates Example: concept CustomerCase CustomerCase( ) subConceptOf ServiceOrderRequest forall.x (¬CustomerCase(x) or ServiceOrderRequest(x)) description impliesType _string description(, ) hasCaseID impliesType CaseID hasCaseID(, ) caseType impliesType _string caseType(, ) customer impliesType TP_Customer customer(, ) requestedService impliesType TelcoService requestedService(, ) Ontology

19 Technical Task Fair December 2007 Web Services & Goals Must import the domain ontology Preconditions –Variables are treated as inputs –Including shared variables Postconditions/Effects –Variables are treated as outputs –Excluding shared variables Only conjunctions are allowed in these constructs Assumptions –Ignored Moreover: –Variables must be bound to a membership –Renaming of variables which are not shared but appear in both pre & post –Negation is also supported

20 Technical Task Fair December 2007 Web Services: Example webService _" importsOntology _" capability billingActivationCapability sharedVariables {?case, ?status, ?cId} precondition billingActivationCapability WebService: BillingActivation definedBy Input: case, status, service, cId ?case[ Output: hasStatus hasValue ?status, Precond: requestedService hasValue ?service, CustomerCase(case) hasCaseID hasValue ?cId OrderStatusContractArchived(status) ] memberOf tp#CustomerCase Service(service) and ?status memberOf tp#OrderStatusContractArchived CaseID(cId) and ?cId memberOf tp#CaseID hasStatus(case,status) and requestedService(case,service) ?service[ hasCaseID(case,cId) isActive hasValue _boolean("true") isActive(service) ] memberOf tp#Service. Postcond: CustomerCase(case) postcondition po OrderStatusBillingActive(status) definedBy hasStatus(case,status) ?case[ haseCaseID(case,cId) hasStatus hasValue ?status, hasCaseID hasValue ?cId ] memberOf tp#CustomerCase and ?status memberOf tp#OrderStatusBillingActive.

21 Technical Task Fair December 2007 Talk Outline Conceptual Background (Jörg) –WSC Formalism –Search States –Heuristic Function –TPSA Results Prototype Demo (James) –WSML Models –The Tool in Action

22 Technical Task Fair December 2007 Questions & Answers Thank You!