tailieunhanh - software engineering ian sommerville 8th edition phần 10

Đội CC và CD đã được tìm thấy để tạo ra các khuyết tật ít hơn đội DD, nhưng những dữ liệu này có nhiều việc phải làm với các hoạt động đảm bảo chất lượng cụ thể được áp dụng bởi nhóm nghiên cứu. Đội phân cấp thường yêu cầu thêm thời gian để hoàn thành một dự án hơn so với một cấu trúc tập trung | 762 Chapter 31 Service-oriented software engineering figure Service construction by composition are available. The hotel booking service reports this lack of availability. This is not a failure lack of availability is a common situation. You then have to undo the flight booking and pass the information about lack of availability back to the user. He or she then has to decide whether to change their dates or their resort. In workflow terminology a compensating action is used to undo actions that have already been completed. The process of designing new services by composing existing services is essentially a process of software design with reuse Figure . Design with reuse inevitably involves requirements compromises. The ideal requirements for the system have to be modified to reflect the services that are actually available whose costs fall within budget and whose quality of service is acceptable. In Figure 1 have shown six key stages in the process of service construction by composition 1. Formulate outline workflow In this initial stage of service design you use the reqmrements for the composite service as a basis for creating an ideal service design. You should create a fairly abstract design at this stage with the intention of adding details once you know more about available services. 2. Discover services During this stage of the process you search service registries to discover what services exist who provides these services and the details of the service provision. 3. Select possible services From the set of possible service candidates that you have discovered you then select possible services that can implement workflow activities. Your selection criteria will obviously include the functionality of the services offered. They may also include the cost of the services and the quality of service responsiveness availability etc. offered. You may decide to choose a number of functionally equivalent services which could be bound to a workflow .