Migration of a Chosen Architectural Pattern to Service Oriented ...
Migration of a Chosen Architectural Pattern to Service Oriented ... Migration of a Chosen Architectural Pattern to Service Oriented ...
Chapter 4. Service Oriented Architecture 86Figure 4.2: Service Oriented Architecture on three levels of abstraction. Adoptedfrom [46]Despite all the benefits associated with more complex concepts of SOA, itshould be kept in mind that an architect should not introduce additional complexityif the system does not require it. The system should be enough complexto support desired objectives and not more.4.5 SOA VendorsIntroduction of SOA to a company is not an easy task. This difficultly hasbeen noticed by leading software developing companies, what resulted in a numberof supporting frameworks and developer’s suits. The solutions that havebeen proposed differ in scope of support but also in understanding of SOA, what(paradoxically) contributes to companies introducing SOA because SOA is vendorindependent and the diversity allows an architect to create more complex(and cheaper) solutions. List of SOA vendors is relatively long (see [15]) and isstill growing. Some vendors provide sophisticated solutions that allow creatingapplication from concept to detailed plan, while other vendors provide plugginsto IDEs. According to [5][80] IBM is one of the leading vendor in supportingSOA and has the highest market share, therefore, it is worth to outline brieflySOA IBM concept and supporting tools.4.5.1 IBM –Layers of abstractionHowever basic concepts of Service Oriented Architecture like service, ESB or orchestrationare very similar to presented in 4.1, the structure of SOA is slightlydifferent. It is said that: “Any problem in computer science can be solved by
Chapter 4. Service Oriented Architecture 87adding a layer of indirection” and IBM leverages this solution very well. Considerationof a system on different layers of abstraction helps to underline bothbusiness and technical aspects. According to IBM, a system should be consideredon five layers of abstraction during SOA analysis. Starting from the mostabstract enterprise level and ending on very precise object level (see figure 4.3).The layers and their role are following[13]:Enterprise layer – describes an enterprise on business model level. The modelconsists of processes, services (as activities) and enterprise data as well as relationshipbetween those elements.Process layer – Process layer consists of main processes which handle mainbusiness concern by composition and decomposition [83]. Composition createsbusiness services from underlying service layer, whereas decomposition decomposesexiting process into services.Service layer – Service layer contains services that expose technical and businessfunctionality of an application [13]. The services are independent and carryindividual tasks. Those services are also building blocks used by Process Layer.Component layer – On component layer, the system is considered as a set ofphysical components - building blocks of services. This layer is very importantbecause components that exist in more than one place are identified [13]. In resultthose components become potential candidates for becoming services or parts ofa service.Object layer – Object layer is the lowest modelled layer during analysis anddesign activities. However the name refers to objects -instances of classes - thelayer contains description of objects understood as classes characterised by operations,attributes and relationship between them [13].4.5.2 IBM – SOA Foundation SuiteSOA Foundation Suite by IBM is a set of SOA supporting tools. Very importantaspects of IBM solution are modularity which enables usage of only a subsetof all the tools and scalability that simplifies architecture modernization whena company grows [60].The tools support different aspects of SOA like ServiceDesign, Creation, Governance, Integration, Connectivity and Collaboration aswell as Service Security. A short characteristic of the tools supporting differentaspects of SOA is following:
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Chapter 4. <strong>Service</strong> <strong>Oriented</strong> Architecture 87adding a layer <strong>of</strong> indirection” and IBM leverages this solution very well. Consideration<strong>of</strong> a system on different layers <strong>of</strong> abstraction helps <strong>to</strong> underline bothbusiness and technical aspects. According <strong>to</strong> IBM, a system should be consideredon five layers <strong>of</strong> abstraction during SOA analysis. Starting from the mostabstract enterprise level and ending on very precise object level (see figure 4.3).The layers and their role are following[13]:Enterprise layer – describes an enterprise on business model level. The modelconsists <strong>of</strong> processes, services (as activities) and enterprise data as well as relationshipbetween those elements.Process layer – Process layer consists <strong>of</strong> main processes which handle mainbusiness concern by composition and decomposition [83]. Composition createsbusiness services from underlying service layer, whereas decomposition decomposesexiting process in<strong>to</strong> services.<strong>Service</strong> layer – <strong>Service</strong> layer contains services that expose technical and businessfunctionality <strong>of</strong> an application [13]. The services are independent and carryindividual tasks. Those services are also building blocks used by Process Layer.Component layer – On component layer, the system is considered as a set <strong>of</strong>physical components - building blocks <strong>of</strong> services. This layer is very importantbecause components that exist in more than one place are identified [13]. In resultthose components become potential candidates for becoming services or parts <strong>of</strong>a service.Object layer – Object layer is the lowest modelled layer during analysis anddesign activities. However the name refers <strong>to</strong> objects -instances <strong>of</strong> classes - thelayer contains description <strong>of</strong> objects unders<strong>to</strong>od as classes characterised by operations,attributes and relationship between them [13].4.5.2 IBM – SOA Foundation SuiteSOA Foundation Suite by IBM is a set <strong>of</strong> SOA supporting <strong>to</strong>ols. Very importantaspects <strong>of</strong> IBM solution are modularity which enables usage <strong>of</strong> only a subset<strong>of</strong> all the <strong>to</strong>ols and scalability that simplifies architecture modernization whena company grows [60].The <strong>to</strong>ols support different aspects <strong>of</strong> SOA like <strong>Service</strong>Design, Creation, Governance, Integration, Connectivity and Collaboration aswell as <strong>Service</strong> Security. A short characteristic <strong>of</strong> the <strong>to</strong>ols supporting differentaspects <strong>of</strong> SOA is following:
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