Migration of a Chosen Architectural Pattern to Service Oriented ...

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Chapter 4. Service Oriented Architecture 80Figure 4.1: Relationship between SOA elements4.3 SOA – business point of viewOne of the goals of SOA is to align the business. It is very important toestablish business context and define boundaries of the system by a managementteam[6].There is no SOA without proper analysis. The need of properbusiness analysis in order to separate services and their relationships was notifiedand resulted in organized methodologies like Service Oriented ModelingAnalysis (SOMA) [6],[11] and supporting Service Oriented Modeling Framework(SOMF) [11]. There are also other approaches like presented by T.Erl [19] or N.Bieberstein[13]. This section presents SOA from business perspective.1. Properties of Services – presents basic properties of services.2. Activities – describes activities executed during designing SOA.4.3.1 Properties of ServicesCompanies that decided to introduce Service Oriented Architecture to their systemschoose also specific approach for analysis and design. Analysis selects themost suitable candidates for services. Each candidate is characterized by followingproperties [13]:reuse, encapsulation, coupling, cohesion and granularity.Reuse – services should be designed keeping high reuse in mind. The importanceof service reuse is explained in details in benefits section (4.7), which fullymotivate high reuse of a service.Encapsulation [13] – hides implementation information from customers of aservice by making services accessible only via their interfaces. There are consumerswho consume the service. The consumption shall not depend on underling
Chapter 4. Service Oriented Architecture 81implementation details, because the consumer is interested only in the result ofinvoked operations. There are also providers who have to design services as technicallyindependent as possible. This independency allows consuming service’soperations by any potential consumer. Each service should have possible highestencapsulation.Coupling – ddescribes dependencies between services. This term in case ofservices is much broader then coupling between components. Coupling refersalso to [13]:1. localisation –the localization of a service should not determinate behaviorand accessibility of a service. To achieve low localization coupling, servicesshould be accessible via configurable component like Gateway [59], EnterpriseService Bus (ESB)[59] or Repository [31]2. technology – the implementation technology of the service cannot determinepossible consumers. To eliminate technology coupling open -standardsfor both transport and messaging like [13]SOAP,XML, TCP/IP are recommended.There is also coupling between [13], message formats, languages, network protocolsand interface contracts but they are consequences and special cases of previouslydescribed cases. The aim for architects and designers is to keep servicesloosely coupled.Cohesion – cohesion refers to relations between operations offered by a service.If operations relate to each other by sharing the same data and/or references toobject then the cohesion is high. A low cohesion means that operations are notrelated to each other or the types of arguments of operations are primitives. Thehigher cohesion a service has, the more flexible and reusable is. Consequently, agood service is characterised by a high cohesion.Granularity – granularity describes size of a service. The size is consideredin two dimensions [13].The firs perspective is the size that can be fine or coarse.The second is a purpose, which can be business or technical. Literature pointssize of a service as factor determining granularity but it also does not provide anymeasure which can conclude that a service characterized by a particular size isfine/coarse grained. In practise [13], coarse-grained services are mainly invokers,while fine grained are invoked . Other definition says that a coarse-grained serviceis a service that provides significant business capability [49]. This definition alsodoes not define how to measure this signification.
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Master ThesisSoftware EngineeringTh
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AbstractContext: Several examples o
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List of Figures1.1 Research methodo
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List of Tables3.1 Summary of archit
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3.3.1 Definition of Pattern Languag
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Chapter 1Introduction1.1 Background
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Chapter 1. Introduction 3technique
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Chapter 1. Introduction 5was notice
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Chapter 1. Introduction 7do not pro
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Chapter 1. Introduction 9Chapter 4
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Chapter 2. Related Work 11This chap
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Chapter 2. Related Work 13(b) Chara
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Chapter 2. Related Work 15Figure 2.
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Chapter 2. Related Work 17Drawbacks
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Chapter 2. Related Work 19Figure 2.
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Chapter 2. Related Work 21Advantage
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Chapter 2. Related Work 23between a
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Chapter 2. Related Work 252. Applic
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Chapter 2. Related Work 274. Mediat
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Chapter 5. Guidelines 131puter (ext
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Chapter 5. Guidelines 133Group 3 ma
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Chapter 5. Guidelines 135Output: Du
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Chapter 5. Guidelines 137generation
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Chapter 5. Guidelines 139(a) Fronte
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Chapter 5. Guidelines 141Figure 5.1
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Chapter 5. Guidelines 143Figure 5.1
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Chapter 5. Guidelines 145FrontendSc
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Chapter 6. Conclusion 147There are
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Chapter 6. Conclusion 149RQ.6 How t
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References[1] http://www.soa-manife
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References 153[22] Frank Buschmann,
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References 155[46] Dirk Krafzig, Ka
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References 157[67] Xiaohong Qiu. Bu
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