TUNABLE DIELECTRIC RESONATOR: DESIGN AND PARAMETERS

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SLA-AWARE APPROACH FOR DYNAMIC WEB SERVICE COMPOSITION ... all classes of non-functional parameters and providing run-time support and ...
SLA-AWARE APPROACH FOR DYNAMIC WEB SERVICE COMPOSITION Pukhkaiev D.S., Kot T.N., Globa L.S., Schill A. Dresden University of Technology, Department of Computer Sciences Dresden, Germany National Technical University of Ukraine “KPI” Institute of Telecommunication Systems 37, Pobedy Ave., Kiev, 03056, Ukraine Ph.: (+38 067) 4022826, e-mail: [email protected] Abstract — This paper provides SLA-aware dynamic Web Services Composition approach and its software implementation that allows performing composition supporting all classes of non-functional parameters and providing run-time support and dynamic reconfiguration at the same time.

ПОДХОД К ДИНАМИЧЕСКОЙ КОМПОЗИЦИИ ВЕБ СЕРВИСОВ С УЧЕТОМ SLA Пухкаев Д. С., Кот Т. Н., Глоба Л. С., Шилль А. Технический университет Дрезден, Факультет компьютерных наук Дрезден, Германия Национальный технический университет Украины Институт телекоммуникационных систем пр. Победы, 37, Киев, 03056, Украина тeл.: (+38 067) 4022826; E-mail: [email protected] Аннотация — В работе представлен анализ существующих методов для динамической композиции веб сервисов (табл. 1). Результаты анализа показали, что ни один из существующих методов не предоставляет композицию с учетом всех QoS параметров. В свою очередь использование Service Level Agreement (SLA) позволяет учесть различные вариации этих параметров, а также распространить действие метода композиции на стадию диагностики (табл. 2). В качестве основы для нового подхода выбран метод на основе онтологий, сравнение этого метода с предложенным подходом представлено на рис. 1. Также предложена программная реализация для подхода (рис. 2), в данный момент находящаяся на этапе разработки.

I. Introduction Web services technology utilization has a considerable advantage — the possibility of connecting them together in order to create an implementation of high level business process. Web Service Composition (WSC) is a method that allows performing such connections. Fast changes of requirements demand dynamic composition and reconfiguration of services, considering required values of functional and non-functional parameters (which represent Quality of Service (QoS) characteristics i.e. reliability, availability, response time, cost, etc.). Functional WSC has been widely researched in literature, the assessment criteria related to non-functional attributes significantly increases the number of requirements for composition. They also can be used for ranking of the composite service or for further results. The first problem of WSC is that QoS parameters should be taken into account on stages of Process enactment and Diagnosis. Another problem of WSC regarding QoS parameters is that despite the existence of various dynamic composition approaches there is no approach which combines evaluation of different classes of QoS parameters during performing composition and none of them is able to meet all QoS requirements.

ll. QoS-Based Comparison of WSC Approaches Web-oriented applications development is implemented by three major stages. First stage is Workflow design which analysis is given in [1]. Next stage is Workflow enactment. This stage’s analysis is given in [2]. These two stages are connected via a graphical standard into execu-

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tion standard translation [3]. The third stage is Workflow analysis short overview of which is presented in [1]. In order to achieve the required effect the individual services are combined into a single service which is called a composite service. Automatic Web service composition consists of four phases: Planning, Discovery, Selection, and Execution [4]. Table 1 provides the comparison of several WSC approaches with respect to QoS characteristics such as Objective and Subjective QoS, Run-time support, QoS assignment to composite service, Quality Requirements. Table 1. QoS-based comparison of WSC approaches Табл. 1. Сравнение подходов композиции веб сервисов по параметрам QoS Requirements Objective QoS Subjective QoS Runtime support QoS assignment Quality Requirements

WSC approaches Markov Chains +

Quality Vector +

Agentoriented +

Ontology-based +

-

-

-

+

+

-

+

-

-

+

+

-

Low

Averag e

High

High

An analysis of the Table 1 shows that current stateof-the-art QoS models of WSC are far from ideal. None of the presented approaches is able to meet all quality requirements. Markov chains solution and Quality Vector solution showed weak results regarding this characteristic while Ontology [5] and agent-based solutions showed

2013 23rd Int. Crimean Conference “Microwave & Telecommunication Technology” (CriMiCo’2013). 9—13 September, Sevastopol, Crimea, Ukraine  2013: CriMiCo’2013 Organizing Committee; CrSTC. ISBN: 978-966-335-395-1. IEEE Catalog Number: CFP13788

good results although there are still some types of QoS parameters i.e. non-measurable parameters [6] that should be considered. Composite service can be easily created and monitored by applying SLA to WSC methods. Applying SLA to methods mentioned above provides results which have significant improvements in comparison to the results presented in Table 1. Table 2 summarizes the results. Table 2. QoS-based SLA-aware comparison of WSC approaches Табл. 2. Сравнение подходов композиции учитывающих SLA веб сервисов по параметрам QoS Requirements

Objective QoS Subjective QoS Runtime support QoS assignment Quality Requirements

Markov Chains

WSC approaches Quality AgentVector oriented

+ -

+ -

+ -

Ontologybased + +

+

+

+

+

+

+

+

+

Low

Averag e

High

High

Table 2 shows that applying SLA to WSC methods provides Run-time support and QoS assignment (assuming that WS-Agreement (WSA) will be generated for composite service using WSA of single services) for all approaches. Analyzing Table 2 we can state that Ontology-based WSC approach combined with SLA-awareness should be able to perform the most reliable WSC of all the approaches mentioned above.

III. SLA-Aware WSC Approach Applying SLA to Ontology-based WSC approach model provides: — substitution of consumer’s and provider’s policies by WSAs which provide the composition with the set of functions that makes the utilization of these policies redundant. — addition of monitoring stage: evaluation of QoS parameters during execution and composite Web Services reconfiguration in case of values violations. Classic Ontology-based approach and the approach which emerged from combination of Ontology-based approach and SLA-awareness are presented on Fig.1.

Utilization of SLA in proposed approach provides a generalized way of storing QoS parameters for service providers. It helps performing WSC on the stage of workflow enactment as well as on the stage of workflow analysis. Another advantage is enabling of run-time monitoring of the composite service. Software implementation for SLA-aware WSC on the Workflow execution stage (Fig. 2) performs the following: 1) extracts the information about functional parameters from abstract BPEL-file; 2) searches for appropriate services in UDDI; 3) extracts SLA information through WSA; 4) makes the decision on which service to utilize basing on WSA and Ontology Data; 5) Creates list of QoS-aware services; 6) Performs composition into executable BPEL-file according to the information from the abstract BPEL-file.

Fig. 2. Structural scheme for software implementation of SLA-aware WSC. Рис.2. Структурная схема программной реализации подхода к композиции веб сервисов с учетом SLA

lV. Conclusion The analysis of state-of-the-art WSC approaches has been made and it showed that none of them is able to meet all QoS requirements. SLA-aware approach for WSC which satisfies all of them has been presented in this paper. The approach allows performing dynamic composition based on SLA, providing required values of QoS parameters, improving general QoS and decreasing service development and re-engineering time. Software implementation for proposed approach on the stage of Workflow enactment was presented. Future work will focus on the implementation of the software realization with its efficiency and results testing.

V. References

Fig. 1. a) Classic Ontology-based approach, b) SLA-aware WSC approach. Рис. 1 а) Подход на основе онтологий, б) Подход учитывающий SLA

[1] Kot T., Reverchuk A., Globa L., Schill A. A Novel Approach to Increase Efficiency of OSS/BSS Workflow Planning and Design. BIS 2012, 2012, pp.142-152. [2] Ko R.K.L., Lee S.S.G., Lee E.W. Business process management (BPM) standards: a survey. Business Process Management Journal, 2009, vol. 15, pp. 744-791. [3] Puhkaev D., Kot T. Conversion of business-processes of extended BPMN into BPEL code. CriMiCo’12, Sevastopol, 2012, pp. 411-412. [4] Cardoso J., Sheth A. Semantic Web Services. Processes and Applications. Springer, 2006. [5] Maximilien E.M., Singh M.P. A framework and ontology for dynamic web services selection. IEEE Internet Computing, 2004, vol. 8, pp. 84-93. [6] Lin M., Xie J., Guo H., Wang H. Solving Qos-driven Web Service Dynamic Composition as Fuzzy Constraint Satisfaction. Proc. of the IEEE International Conference on eTechnology, e-Commerce and e-Service, 2005, pp. 9-14.

2013 23rd Int. Crimean Conference “Microwave & Telecommunication Technology” (CriMiCo’2013). 9—13 September, Sevastopol, Crimea, Ukraine  2013: CriMiCo’2013 Organizing Committee; CrSTC. ISBN: 978-966-335-395-1. IEEE Catalog Number: CFP13788

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