A Declarative Approach for QoS-Aware Web Service Compositions

Abstract

While BPEL language has emerged to allow the specification of Web Service compositions from a functional point of view, it is still left to the architects to find proper means to handle the Quality of Service (QoS) concerns of their compositions. Typically, they use ad-hoc technical solutions, at the message level, that significantly reduce flexibility and require costly developments. In this paper, we propose a policybased language aiming to provide expressivity for QoS behavioural logic specification in Web Service orchestrations, as well as a non-intrusive platform in charge of its execution both at pre-deployment time and at runtime.

Aspectual session types

“…Therefore, they must possibly be realizable at any point, in parallel with the participant's original activity. This is why Rule (TDaemon) rewrites the local type to introduce a fork that branches between the original activity (which starts at x) and the advice activity 2 . In addition, the advice activity must possibly be executed several times.…”

“…Otherwise the underlying protocols often have to be extensively rewritten, thus complexifying the protocol structure, a tedious and error-prone task. Aspect-oriented systems have been proposed for this purpose, notably to manipulate service orchestrations modularly, for example, using AO4BPEL [6] and in particular for the control of the QoS properties of orchestrations [2]. However, no aspect system exists that enables the modification of session types while maintaining their strong correctness guarantees.…”

BPRules and the BPR-Framework: Comprehensive Support for Managing QoS in Web Service Compositions

“…We assume that there are multiple concrete services that provide this functionality but at different QoS levels. Selecting the right concrete services for the composition is known as the service selection problem and is known to be NP-hard [9]. We give a short insight of how we handled this problem in section 3.1 and further details can be found in [4].…”

“…By addressing QoS requirements for services, our BPRules language has similar goals as the two languages Quality of Service Language for Business Processes (QoSL4BP) [9,10] and the Web Service Requirements and Reactions Policy (WS-Re2Policy) [5] language. All three languages have a similar structure by means of specifying actions to be undertaken upon QoS violations.…”

“…Also BPRules provides increased flexibility for the QoS data retrieval for past and/or running process executions, and an advanced control and decision support for the business analyst. Similar to the section control feature from BPRules, the authors from [9] are able to query structured activities for QoS. However, they cannot relate QoS parameters from different sections like in BPRules (e.g: the response time from the distributor section is less than 1/2 of the response time of the bookshop process).…”