Dipl.-Wirtsch.-Inform. Michael Spahn
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WSQoSX – A QoS architecture for Web Service workflows
In: 5th International Conference on Service-Oriented Computing (ICSOC 2007), Demo Track; Vienna, Austria
Reference No.: 2007-726
Dynamic Replanning of Web Service Workflows
In: IEEE International Conference on Digital Ecosystems and Technologies 2007 (IEEE DEST 2007); Cairns, Australia
Reference No.: 2007-429
Heuristics for QoS-aware Web Service Composition
In: 4th IEEE International Conference on Web Services (ICWS 2006); Chicago, USA
This paper discusses the Quality of Service (QoS)-aware composition of Web Services. The work is based on the assumption that for each task in a workflow a set of alternative Web Services with similar functionality is available and that these Web Services have different QoS parameters and costs. This leads to the general optimization problem of how to select Web Services for each task so that the overall QoS and cost requirements of the composition are satisfied.
Current proposals use exact algorithms or complex heuristics (e.g. genetic algorithms) to solve this problem. An actual implementation of a workflow engine (like our WSQoSX architecture), however, has to be able to solve these optimization problems in real-time and under heavy load. Therefore, we present a heuristic that performs extremely well while providing excellent (almost optimal) solutions. Using simulations, we show that in most cases our heuristic is able to calculate solutions that come as close as 99% to the optimal solution while taking less than 2% of the time of a standard exact algorithm. Further, we also investigate how much and under which circumstances the solution obtained by our heuristic can be further improved by other heuristics.
Reference No.: 2006-291
An Approach for Replanning of Web Service Workflows
In: Americas Conference on Information Systems (AMCIS 2006); Acapulco, Mexico
The dynamic composition of Web Services to workflows at runtime is a major challenge in the emerging field of Service-oriented computing. At this, preferences and constraints defined by the user have to be considered, e.g. executing a workflow with the cheapest Web Services, but not exceeding a given execution time. Due to the volatile nature of the Web Service environment the actual runtime behavior of Web Services may deviate from the one estimated in the planning phase. Thus, replanning mechanisms are crucial for adapting a workflow to the real behavior ensuring that its execution remains feasible, valid and optimal subject to the preferences and constraints defined by the user. Replanning mechanisms have to perform in real-time not to create further delay to the workflow execution. Thus, in this paper, we introduce a heuristic based replanning mechanism.
Reference No.: 2006-110