Tuesday, May 29, 2012 Towards Automatic Non-Deterministic Web Service Composition Markou, G. &...

Tuesday, May 29, 2012

Towards Automatic Non-Deterministic Web Service

Composition

Markou, G. & Refanidis, I.Dept. of Applied Informatics, University of Macedonia, Greece

ICIW 2012 - Web Services-based Systems & Applications IV


In Summary

• Introduction• Related Work

o Method of Choiceo Use of Standardso Onlineo Evaluation

• Proposed Approach

• Evaluation o Quantitative criteriao Use case scenarios

• Conclusion

ICIW 2012 - Web Services-based Systems & Applications IV 2/31

o Application o Registryo Web Service Editor

o Translation between AI & Web Service languageso Manual Web Service Composition moduleo Automatic Web Service Composition module




• Proposed Approach o Application o Registryo Web Service Editoro Translation between AI & Web Service languageso Manual Web Service Composition moduleo Automatic Web Service Composition module


• Conclusion



Motivation

• Difficult to expect from a human user /experts to manually complete the goal of a Web Service Composition (WSC)o Number of Web Services (WSs) is growing continuously

discovery phase more difficulto Ever-changing environment: WSs can change interfaces or even part of

their usage multiple times throughout their lifespano Always possible that their execution is not successful



System Goals - Functionalities:

• Online• Registry / Advertisement / Semantic search of Web Services• Editing of Web Services • Translation/ mapping between AI & Web Service languages• Manual Web Service composition module• Automatic Web Service composition module• Evaluation based on

o Quantitative criteriao Use case scenarios



• Introduction

• Related Worko Method of Choiceo Use of Standardso Onlineo Evaluation



• Conclusion



Method of Choice (1/2)

• Method of choice?• Use of standards?


• Most widespread: AI planning • Diverse

o OWL-S / PDDL widely usedo Other standards (e.g., WSMO)o Proprietary formats

Perhaps most notable is Sirin, et al. (2004)o From WSC problem (described in OWL-S) to HTN o Composite process that can be decomposed to simpler ones

Simple processes being atomic WSso Reduces complexity of the planning process o Cannot cope with non-determinism o Planner-dependent


Method of Choice (2/2)

• AI planning also used in Hoffmann, et al. (2009)o Treats the application of a WS as a belief update operationo Identifies tractable special cases of WSC

Allow for a compilation into planning under uncertainty o Subsequent use of existing conformant planner o PDDL-like problem descriptions o No standardized WS description



Use of Standards

• Klusch, Gerber & Schmidt (2005) and Hatzi, et al. (2011) rely on translation of OWL-S descriptions to PDDL problems o Klusch, Gerber & Schmidt (2005):

Outputs modified PDDL files (in XML) Does not have evaluation on WSC problems

o Hatzi, et al. (2011) tackles uncertainty with re-planning module o Both only address WSC problem, not other stages



Online

• YaWSA (Macdonald, 2007)o Only web-based WSC system in literature with running demo o Only implemented a WSC process (no registry, view WSs’, etc)o No longer available for public use

• Prototype web-based WSC system described in Du, Song, and Munro (2006)o Supporting multiple phases of WSC o Public link to running demo of their implementation is not provided



Evaluation

• Literature suggests a gap in the evaluation process of the current WSC systemso Many simply evaluate their methodology on a single case study,

without referring to quantitative criteria, e.g., Chen, Xu, and Reiff-Marganiec (2009), McDermott (2002), McIlraith and Son (2002)

• Notable exceptions:o Hoffmann, et al. (2009) : Two artificial benchmarks with different encodings and

plannerso Hatzi, et al. (2011): Single use case, with different number of WSs

Test collection combination of hand-tailored atomic WSs and entire domains of OWL-S Service Retrieval Test Collection (OWL-S TC)

o Kona, et al. (2008): Three versions of a single use case, each suited for a mode of their WSC algorithm

Test collection: Modified version of the 2006 WS-ChallengeICIW 2012 - Web Services-based Systems & Applications IV 11/31






• Conclusion



Proposed Approach - Application


User email registration

Initial screenBased on Google Web Toolkit (GWT):


Registry (1/2)

• Core of the application is based on iServe o Open platform for publishing and discovering serviceso WSs are semantically described in OWL-S, not Minimal Service Modelo Used its web-based application for

Browsing QueryingUploading services

o Populated the registry with version 4.0 of OWL-S TCo Made several improvements to its interface and functionality



Registry (2/2)


Web Service details

Inline operations

Semantic search alternatives


Proposed Approach – WS Editor


XML Editor with syntax highlighting

Pre-defined OWL-S templates


Translation between AI & WS Languages

• AI planning language: PDDL, the de facto planning language o Specifically, NuPDDL

Compatible with PDDL2.1, retaining most of itCapable of modeling non-deterministic action effects (one of, unknown)

• WS semantic description language: OWL-S, most widely usedo Heavily influenced from planning languages, such as PDDL

• Partial mapping from OWL-S to PDDL existso Part of it straightforward:

ServiceProfile input parameters identically named ones of PDDL actionhasPrecondition/ hasEffect parameters precondition/ effect of action

o Conversion of non-physical knowledge from OWL-S to PDDL problematic Introduction of new predicate in PDDL domain?



Manual WSC Module

• Under implementationBased on PetalsBPMModification from BPMN 2.0 editor to suit OWL-S WSC functionalitiesTo be compared with automatic WSC module (ease of use, speed, etc)



Automatic WSC Module

• Future work – Basic directions:o WSs may fail to execute correctly, e.g.,

Unavailability of an atomic WS involved in the planOutput of their successful execution is not the expected one

o Generate plans tackling the most influential and likely contingencieso Proposed solution based on contingent planning

Produce seed planExamine for significant/ likely points of failureAdd conditional branchesRe-planning module will be integrated







• Conclusion



Quantitative Criteria

• Criteria to be considered:o Number of Web Services considered for WSCo Preprocessing time (parsing of ontologies’ concepts, etc)o Transformation time (of WS domain to PDDL one)o Planning time (to output a successful plan)o Optimality of the outputted plans (least WSs used to achieve the

required goal)



Use Case Scenarios

• Based on OWL-S TC Semantic Web Services v. 4.0 (PDDL)o Each scenario uses a subset of descriptions of an OWL-S TC domain o A few semantic WS descriptions were added for testing purposes, and

some were modified

• Each scenario with increasing non-determinism & complexity



Movie Database Scenario (1/2)

1) Movie database search using a (partial) movie title o Based on Communication domain: 58 semantic WSs in totalo Fully deterministic - Serialized composite WS output o Retrieve comedy films with titles similar to user inputo Output:

Movie titlesPricing information (tax-free price, recommended price, etc)



Movie Database Scenario (2/2)

Composite Web Service (created through Manual WSC module)



Online Bookstore Scenario (1/2)

2) Online bookstore product purchaseo User wants to purchase a book from an specific online bookstore with a

preferred method of paymento Preferences regarding method of paymento Based on Education domain: 285 semantic WSs in totalo Non-deterministic output

Different outcomes: Output if book in stock:

Addition of book in shopping cart Purchase with the specified method of payment Output information regarding it, such as its author

No output if book not in stock



Online Bookstore Scenario (2/2)




Camera Search Scenario (1/2)

3) Camera search and purchaseo User want to purchase an analog SLR model; willing to

settle for other ones if it is not in stockUser preference towards specific modelMore than one sellers exist

o Based on Economy domain: 359 semantic WSs in totalo Possible iteration in output Web Service

Since more than one sellers exist, if product not available at one, check another

If product not found in any of the sellers, try with other versions (digital SLR, simple compact cameras)



Camera Search Scenario (2/2)








• Conclusion



Conclusion

• Current WSC approaches, in general:o Do not deal with inherent non-determinism in WSC domaino Are not online, despite WS’ use & nature being web-orientedo Do not evaluate their methodology using well defined

scenarios or test sets Improvements have been made recently

• Our final system is intended to be the first online and open source system supporting multiple phases of WSC

• Presented scenarios provide efficient way of evaluationo Can be used by other WSC works as a common test bed



Thank you for your attention!

Questions?


Tuesday, May 29, 2012 ICIW 2012 - Web Services-based Systems & Applications IV 32/31Extra Slides


References:Referenced papers:• E. Sirin, B. Parsia, D. Wu, J. Hendler, and D. Nau, “HTN planning for web service composition using SHOP2”, J. Web

Semant., vol. 1, no. 4, Oct. 2004, pp. 377-396.• J. Hoffmann, P. Bertoli, M. Helmert, and M. Pistore, “Message-based web service composition, integrity constraints,

and planning under uncertainty: a new connection”, J. Artif. Intell. Res, vol. 35, May 2009, pp.49-117.• M. Klusch, Α. Gerber, and M. Schmidt, “Semantic web service composition planning with OWLS-Xplan”, Proc. 1st

International AAAI Fall Symposium on Agents and the Semantic Web, Nov. 2005.• O. Hatzi, D. Vrakas, M. Nikolaidou, et al., “An integrated approach to automated semantic web service composition

through planning”, IEEE Trans. Service Computing, April 2011, pp. 301-308.• A. Macdonald, “Service composition with hyper-programming”. Technical Report, University of St Andrews, 2007.• X. Du, W. Song, and M. Munro, “Using common process patterns for semantic web services composition”, Proc.

15th International Conference on Information Systems Development (ISD’06), Sept. 2006.• K. Chen, J. Xu, and S. Reiff-Marganiec, “Markov-HTN planning approach to enhance flexibility of automatic web

service composition”, Proc. IEEE International Conference on Web Services (ICWS'09), July 2009, pp. 9-16.• D.V. McDermott, “Estimated-regression planning for interactions with web services”, Proc. Sixth International

Conference on Artificial Intelligence Planning Systems (AIPS ’02), April 2002, pp. 204-211.• S. McIlraith and T. Son, “Adapting Golog for composition of semantic web services”, Proc. 8th International

Conference on Principles of Knowledge Representation and Reasoning (KR2002), April 2002, pp. 482-496. • S. Kona, A. Bansal, M.B. Blake, and G. Gupta, “Generalized Semantics-Based Service Composition”, Proc. IEEE

International Conference on Web Services (ICWS’08), Sept. 2008.

ICIW 2012 - Web Services-based Systems & Applications IV

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