Using context to improve data semantic mediation in web services composition
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Using context to improve data semantic mediation in web services composition. Michaël Mrissa (spokesman) - Philippe Thiran DBDBD’07. Outline. Introduction Web services & composition Semantic Web services Mediation challenges Objectives & contribution Proposition

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Using context to improve data semantic mediation in web services composition l.jpg
Using context to improve data semantic mediation in web services composition

Michaël Mrissa (spokesman) - Philippe Thiran DBDBD’07


Outline l.jpg
Outline services composition

  • Introduction

    • Web services & composition

    • Semantic Web services

    • Mediation challenges

    • Objectives & contribution

  • Proposition

    • Presentation of the context model

    • Context integration with Web services

    • General architecture

    • Mediation & Implementation overview

  • Conclusion & perspectives


Web services composition l.jpg
Web services & composition services composition

  • Software components

    • Interaction model

  • Composition of Web services

    • Value-added composite Web services

    • Objective: answer complex user requests

  • No semantics yet…

  • UDDI repositories

  • WSDL descriptions

  • SOAP messages

Registry

Publish

Find

Travel planning

Bind

Consumer

Provider

WS

Flight booking

Hotel booking

Addition


Semantic web services l.jpg
Semantic Web services services composition

  • The Semantic Web

    • Objectives

      • Better interoperability between information systems

      • Automation of information exchange

    • Means

      • Explicit machine-interpretable semantic descriptions

      • Relies on ontologies [Gruber, 1993]

  • Semantic description of Web Services

    • Semantic languages

      • OWL-S [Martin et al., 2004], WSMO [Arroyo and Stollberg, 2004], DIANE [Klein et al., 2005]

    • Annotation to existing formats

      • WSDL : SESMA [Peer and Vukovic, 2004], WSDL-S [Miller et al., 2004]

      • UDDI : [Paolucci and Kawamura, 2002]


Mediation challenges l.jpg
Mediation challenges services composition

  • In a composition

    • Semantic mediation of exchanged data is required

  • Mediation between (semantic) Web services

    • IRS-III [Cabral and Domingue, 2005],

    • WSMX [Mocan et al., 2004]

    • Agent-based mediation [Williams et al., 2005]

    • Rule-based approach [Spencer et al., 2004]

Travel planning

Semantic heterogeneities

Output

Input

Output

Input

Label conflicts

Web

Service 1

Web

Service 2

PRICE (EUR)

PRICE (USD)

Unit & value conflicts


Objectives contribution l.jpg
Objectives & contribution services composition

  • Multiple goals & constraints

    • Solve data semantic heterogeneities in a composition

    • Ease the task of Web services providers

    • Explicitly describe the semantics of Web services

    • Enable semantic mediation in composition

  • Proposition

    • Use context-based representation of data semantics

    • Rely on contextual ontologies

    • Annotate WSDL language with semantics

    • Detect semantic heterogeneities in the composition

    • Insert mediation mechanisms at the composition level


Outline7 l.jpg
Outline services composition

  • Introduction

    • Web services & composition

    • Semantic Web services

    • Mediation challenges

    • Objectives & contribution

  • Proposition

    • Presentation of the context model

    • Context integration with Web services

    • General architecture

    • Mediation & Implementation overview

  • Conclusion & perspectives


Presentation of the context model l.jpg
Presentation of the context model services composition

  • Definition of “context”

    • Collection of semantic assumptions on data interpretation

    • How should a price be interpreted ? (VAT, currency, scale factor…)

  • The context model contains 4 elements

    • Semantic objects

    • Static modifiers

    • Dynamic modifiers

    • Conversion rules & functions

  • Characteristics of the model

    • Good integration with WSDL

    • Based on the MIX model [Bornhövd, 1999]

    • Definition of static and dynamic modifiers

    • Semantic conversion between semantic objects


Presentation of the context model9 l.jpg
Presentation of the context model services composition

  • A semantic object is a 4-tuple

    • A concept c defined in a domain ontology

    • A value v that contains the data itself

    • A type t that describes the actual type of the value

    • A context C that characterizes the semantic interpretation of S

      • C is described as a set of semantic objects

  • Semantic object in C are called modifiers

    • Modifiers are dynamic iff:

Semantic object S = ( c, v, t, C )

∀ v ∈ S, ∃ f:{Dom(t) ×...× Dom(t)} → Dom(t) ∧ ∃ {S1, ... Si, ... , Sn },

s.t. Si = <ci, vi, ti, Ci> ∈ Ctxt ∧ Si≠ S ∧ f(v1, ..., vi, ..., vn) = v.


Presentation of the context model10 l.jpg
Presentation of the context model services composition

  • A sample semantic object


Presentation of the context model11 l.jpg
Presentation of the context model services composition

  • Conversion possibilities between semantic objects

    • With context conversion functions

      • Change modifiers’ values

      • Dynamic aspect

      • May involve access to remote resources (e.g. currency conversions)

      • Stored as rules

    • With type conversion functions

      • Stored in conversion libraries

      • Related to the type system (XML Schema)

  • Semantic comparability

    • Over a common type and context

    • Different objects still comparable over limited context


Presentation of the context model12 l.jpg
Presentation of the context model services composition

  • Illustration with the travel planning example


Context integration with web services l.jpg
Context integration with Web services services composition

  • Semantic annotation of WSDL metamodel


Context integration with web services14 l.jpg
Context integration with Web services services composition

  • Illustration of our annotation

    • Excerpt of annotated WSDL document

    • Only static modifiers are added to the description

      <?xml version=``1.0" encoding=``UTF-8"?>

      <wsdl:definitions...>...

      <wsdl:message name=``HotelBookingTicket">

      <wsdl:part name=``inputPrice" type=``xsd:double"

      ctxt:context=``dom1:Price ctxt1:France

      ctxt1:VATIncluded ctxt1:ScaleFactorOne"/>

      </wsdl:message>...

      </wsdl:definitions>


Context integration with web services15 l.jpg
Context integration with Web services services composition

  • Context ontologies

    • Store context information for each domain concept

    • Updated by Web services’ providers

    • Separates top-down and bottom-up aspects


Global architecture l.jpg
Global architecture services composition


Mediation implementation overview l.jpg
Mediation & Implementation overview services composition

  • Prototype

    • Implementation of the travel planning example

    • Graphical annotation editor (WSDL4J API)

    • Development of the mediator


Conclusion l.jpg
Conclusion services composition

  • A context-based solution for semantic mediation

    • A model for representing data

    • Separation of domain and context knowledge

    • Annotation of Web services’ descriptions

    • Mediation mechanisms

  • Future work

    • How to insert mediators into the composition ?

      • A first proposal relies on WS-BPEL analysis

      • A language-independent method ?

    • This model applies to Web services, but…

      • What about other semantic tools on the Web ?

      • Microformats, RDFa…

    • To what extent the context model applies to the WWW ?


Thank you l.jpg
Thank you ! services composition

Any questions ?

University of Namur

http://www.fundp.ac.be

PRECISE group

http://www.fundp.ac.be/precise

Contact :


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