Web Service Composition

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What is Web Service Composition?
Two types of WS compositions are prominent. Choreography and Orchestration as we show in the figure.

Services-oriented architecture (SOA) aims to provide a loosely-coupled integration of services residing on different systems, written using different programming languages and with other implementation disparities. Popularly considered as the building block of SOA, Web services (WS) are self-describing and platform-independent applications that can be invoked over the Web. Facilitating the assembly of services to form composite services is an important functionality in SOA. The problem of automatically assembling WSs to form compositions that optimize given user preferences is often referred to as the automated Web service composition problem. It involves two major challenges each with its own attendant issues:

  1. automatically construct the control flow of the composition and
  2. appropriately resolve the data heterogeneity between WSs participating in the composition.
Project Description
The architectural design of Haley, our WS composition tool.

We use a hierarchical decision-theoretic planning framework for composing Web services, called Haley. Compared to classical AI planners, decision-theoretic planning has the ability to model the uncertainty inherent in WSs and provide a cost-based process optimization. Haley uses symbolic planning techniques that operate directly on first order logic based representations of the state space to obtain the compositions. As a result, it supports an automated elicitation of the corresponding planning domain from WS descriptions and produces a compact domain representation in comparison to classical AI planners. Additionally, it tackles the scalability issue by exploiting the natural hierarchy found in processes.

Few implemented tools for Web service composition exist. We implement Haley and provide a comprehensive tool suite. The suite accepts WSs described using standard languages such as SAWSDL. It provides process designers with an intuitive interface to specify process requirements, goals and a hierarchical decomposition, and automatically generates BPEL processes, while hiding the complexity of the planning and BPEL from users.

Project Generated Resources
  • Haley – A Hierarchical Framework for Automatically Composing Web Services
Related Resources
  • WS Composition: Solutions and Challenges
  • Synthy -- End to End Composition and Adaptation of Web Services
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