A Simple Solution for Information Sharing in Hybrid Web Service Composition

Abstract

In hybrid service composition approaches, processes are used to describe the core part of the composition logic whereas the rules are used to specify decision making constraints and conditions. These rules are exposed as services and are used in the processes whenever a certain decision has to be made. To evaluate these rules, we need a mechanism 1) to share data between the main process and the rule service; 2) to decide upon which service to invoke based on the result received from the rule service. In this paper, we propose a tuple space based solution for supporting these requirements. We also include descriptions of an application scenario to motivate our work, a prototype of the proposed solution and we demonstrate how our solution helps in achieving process flexibility with minimal maintenance costs in the context of changing requirements.

Decision as a Service: Separating Decision-making from Application Process Logic

“…Therefore, the process can call the decision service only at its certain decision points. Comparing with [8], [5], our approach supports asynchronous notification between the process and decision service in addition to synchronous request-response interactions.…”

“…In [5], a tuple space has been proposed to provide more flexibility about their data model. In this approach, the data can be added and shared by a process or rule engine on the fly.…”

“…Existing works [8], [5] suggest that a process and a decision service interact with each other in a synchronous requestresponse manner. It means that the process always calls the decision service at some predefined decision points.…”

“…A process logic usually incorporates or has an associated set of (declarative) rules to specify the conditions and constraints on the imperative flows. Since both processes and rules have advantages and disadvantages on their own rights, hybrid service composition (which uses a combination of processes and rules) has been proposed as a plausible solution to support evolvability [5], [6], [7], [8], [9], [10]. However, a process logic can be implemented in rules and some of the rules can be implemented in processes, and finding a balance of what can be specified by the process logic and what by the rules is a serious challenge [11].…”

“…The rules are exposed as an ordinary application service which can be called by the process [8], [5], which we refer to as decision service in this paper. The main idea behind exposing rules as application services is to support flexibility in handling the changes in conditions and constraints.…”