# 电子工程代写|软件项目作业代写Software Project代考|SENG3160

## 电子工程代写|软件项目作业代写Software Project代考|Measurement Strategy Phase

As for any target of a COSMIC measurement, for the SOA it is needed to specify the following elements.

In the case of measurement at the service level, usually the purpose of measurement is the estimation of the effort needed for the development or modification of the system. The measurement can be performed with different scopes. The guideline for SOA [18] distinguishes between the cases where the purpose is to measure a piece of software ‘using’ multiple SOA services and when the purpose is to measure a ‘collection’ of multiple SOA services. For the first cases, the scope should be defined without considering internal data movements. In the latter cases, the size of the distributed application is equal to the sum of the sizes of single services.
What makes the COSMIC method particularly suitable for SOA services is the fact that it allows for the size measurement of multilayer applications. A layer, as defined by COSMIC, provides a set of services, which can be utilised by the software in other layers and can be part of a structure either hierarchical or bidirectional. In particular, in SOA the orchestration services can call application services but not vice versa establishing a hierarchical relationship. Intermediary services can be called by application service and vice versa, and both orchestration and application services can call utility services.

If the services in different layers need to be measured, the measurement scopes must be different. Figure $3.5$ shows that the definition of what is considered as ‘layer’ depends on the ‘view’ of the software architecture. If the purpose is to measure the size of application A ‘as a whole’ as in (a), the measurement scope is the whole of application $\mathrm{A}$ as a single layer. If application $\mathrm{A}$ has been built according to the ‘three-layer’ architecture, the purpose is to measure the three components separately in view (b). In the case of SOA, the measurement scope must be defined separately for each SOA component.

## 电子工程代写|软件项目作业代写Software Project代考|Mapping and Measurement Phase

An FUR of a service may be restricted to define the ‘capability’ it provides for any service requestor, ‘how’ to request the capability and the ‘form and content’ of the request and reply messages. Some requirements that usually are considered as non-functional, in the case of SOA services, may be implemented directly as software and therefore are part of the software. For instance, the security requirements need to follow precise protocols (e.g., OAuth) and the protocols being implemented in the software itself. If the protocol is in the scope of the measurement, it requires being measured as well.

The COSMIC method considers that unique events give rise to one or more functional processes whose role is to respond to the events. The first step for the measurement is to identify these functional processes and events. In the field of SOA, there are no standards about considering whether the concepts of ‘service’ and ‘functional process’ coincide; thus it is not excluded that one service may lead to multiple functional processes.

As mentioned before, the communication between services consists of messages exchanged, and therefore developing a service always involves developing the request/reply mechanism. The exchange between components may be ‘synchronous’ if the requesting service waits for the response before continuing its task. As an example of cloud service, it may be a web server that queries a database service to retrieve information. It can also be ‘asynchronous’ if the requestor functional process does not wait for the response message. For instance, an application service may ask for a time-consuming task to another service, without blocking its task. Once the latter finishes its job, the result can go back to the original requestor. In terms of COSMIC data movements, the main difference between the two kinds of services is that with the asynchronous mode, the arrival of a response message needs to be considered as another event triggering a separate functional process in the requesting software.

Another important thing that a COSMIC measure must deal with when measuring SOA services is the error message management. Technically speaking, in case a requestor calls another service and any issue occurs, the response message is replaced by the error data itself. In terms of COSMIC data movements, an Exit only is considered in any case. Nevertheless, if a confirmation/error message is notified to a human functional user or another service, an additional Exit must be considered.

## 电子工程代写|软件项目作业代写Software Project代考|Mapping and Measurement Phase

COSMIC 方法认为独特的事件会产生一个或多个功能过程，其作用是响应事件。测量的第一步是识别这些功能过程和事件。在SOA领域，对于“服务”和“功能流程”的概念是否一致，没有标准的考量；因此，不排除一项服务可能导致多个功能流程。

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