Automated Situation-Aware Service Composition in Service-Oriented Computing

Abstract

Service-based systems have many applications, such as e-business, health care, and homeland security. In these systems, it is necessary to provide users the capability of composing services into workflows providing higher-level functionality. In dynamic service-oriented computing environments, it is desirable that service composition is automated and situation-aware to generate robust and adaptive workflows. In this paper, an automated situation-aware service composition approach is presented. This approach is based on the a-logic, a-calculus, and a declarative model for situation awareness (SAW). This approach consists of four major components: (1) analyzing SAW requirements using our SAW model, (2) translating our SAW model representation to a-logic specifications and specifying a control flow graph in a-logic as the service composition goal, (3) automated synthesis of a-calculus terms defining situation-aware workflow agents based on a-logic specifications for SAW requirements and the control flow graph, and (4) compilation of a-calculus terms to executable components.

An Approach to Adaptive Distributed Execution Monitoring for Workflows in Service-based Systems

“…This process is based on our previous work on composing, scheduling and deploying workflows in SBS [16,18,19]. We assume that before the process of generating our WF monitors starts, a workflow has been composed [16] or manually defined by developers, and the initial schedule, resource assignment and deployment plan for this workflow have been generated [18,19]. We generate a WF monitor for each resource to be used in the workflow.…”

“…4) Synthesis of AS 3 calculus terms for WF monitors. Similar to our automated agent synthesis approach for situation awareness in SBS, various monitoring activities to be performed by WF monitors can be described using AS 3 calculus [15][16][17], which is based on classical process calculus. AS 3 calculus can model timeouts, failures, service invocations, and communications.…”

“…As discussed in Section 3, our WF monitors will utilize system control services, such as system performance packages, to acquire the status information of various resources. To facilitate the synthesis of WF monitors, these system control services are specified using AS 3 logic in the same way as functional services used by the workflows in SBS [15,16]. Such logical specifications allow the discovery of appropriate system control services through automated reasoning on the service specifications according to the monitoring targets identified in Step 1).…”

“…Such knowledge needs to be specified in a machine-understandable way so that automated reasoning on the knowledge can be performed. In our approach, AS 3 logic [15][16][17] is used to specify the temporal and causal relations between failures. (For example, a simple rule "A→◊B" in AS 3 logic states that the occurrence of an event A may lead to B.)…”

“…An AS 3 calculus to Java compiler has been developed to generate Java code for an executable agent running on our WVMs from the AS 3 calculus terms describing the behavior of this agent [16,17].…”