A Context-Based Mediation Approach to Compose Semantic Web Services Michael Mrissa, Chirine Ghedira, Djamal Benslimane, Zakaria Maamar, Florian Rosenberg, Schahram Dustdar Presented By: Mike Jancar

Outline Current Situation Current Situation Current Research Current Research Limits of Current Approach Limits of Current Approach Proposed Solution Proposed Solution Implementation Implementation Conclusions, Future Work Conclusions, Future Work

Current Situation Data exchange between web services involves significant number of implicit assumptions Data exchange between web services involves significant number of implicit assumptions Semantic web service adds conceptual information Semantic web service adds conceptual information Same domain, different assumptions Same domain, different assumptions Semantic WS an improvement, but does not consider context Semantic WS an improvement, but does not consider context

Current Situation Goal: Automated reconciliation of heterogeneous data exchange Goal: Automated reconciliation of heterogeneous data exchange Two conditions to be met: Two conditions to be met: –Agree on meaning of data –Conflicts in meaning are automatically resolved Answer: Add context Answer: Add context

Current Research Other researchers have focused on two aspects Other researchers have focused on two aspects Create / extend semantic languages Create / extend semantic languages –OWL-S, WSMF, WSDL-S… Automated semantic mediators Automated semantic mediators Neither approach considers context Neither approach considers context

Limits of Current Approach

Flight service – European Flight service – European Car Rental service – Japanese Car Rental service – Japanese Key Data Conflicts Key Data Conflicts –Currency ( Euro vs Yen ) –Scale Format ( 1 vs 1000 ) –Date-Time Format –Value-Added Taxes (VAT, TVA)

Limits of Current Approach Currently, domain ontologies used to describe domain concepts, handle differences Currently, domain ontologies used to describe domain concepts, handle differences Add value, but… Add value, but… –Conversions are identified manually, handled up front –Require expert knowledge –Not possible to do “on-the-fly”

Proposed Solution Context-Based Model Context-Based Model –Semantic objects with contextual descriptions –Extend existing web service description documents ( known as WSDLs ) –Build dynamic mediation architecture

Context-Based Model Semantic Object with Contextual Information Semantic Object with Contextual Information –Extends descriptive capabilities Two Parts Two Parts –Data ( value v of type t ) –Semantic ( concept c with context C ) Two types: Static and Dynamic Two types: Static and Dynamic

Context-Based Model

Context explicitly defined in new context ontologies Context explicitly defined in new context ontologies Extension of domain ontologies – adds context to each concept Extension of domain ontologies – adds context to each concept

Extending the WSDL Web Services Description Language Web Services Description Language XML document that defines a web service XML document that defines a web service Take advantage of extensibility Take advantage of extensibility Increase flexibility and maintainability Increase flexibility and maintainability

Extending the WSDL Only define static modifiers Only define static modifiers Dynamic modifiers can be determined Dynamic modifiers can be determined

Mediation Architecture Need to handle conceptual differences dynamically Need to handle conceptual differences dynamically Utilizes dynamic code generator to create web services “on-the-fly” Utilizes dynamic code generator to create web services “on-the-fly” Follows a three-step process Follows a three-step process

Mediation Architecture Contextualization Contextualization –Analyzes process, identifies data flows Automatic Mediator WS Generation Automatic Mediator WS Generation –Custom web service to fit flow Update Original Process Update Original Process –Insert custom services into process

Mediation Architecture

Implementation Proof-of-concept system built Proof-of-concept system built Uses Java, Apache Web Server Uses Java, Apache Web Server Simple design based on Plane Ticket / Car Rental example Simple design based on Plane Ticket / Car Rental example

Implementation

Conclusions / Future Work Context-based mediation successful in proof-of-concept case Context-based mediation successful in proof-of-concept case More investigation necessary for larger cases More investigation necessary for larger cases Will require involving domain experts with knowledge of larger domains Will require involving domain experts with knowledge of larger domains