tailieunhanh - Software Fault Tolerance Techniques and Implementation phần 4

Đa dạng dữ liệu được trình bày chi tiết hơn trong phần sau. Kỹ thuật sử dụng dữ liệu đa dạng được mô tả trong Chương gian dự phòng liên quan đến việc sử dụng thêm thời gian để thực hiện các nhiệm vụ liên quan đến khả năng chịu lỗi. Nó được sử dụng cho cả phần cứng và khả năng chịu lỗi phần mềm. | Design Methods Programming Techniques and Issues 91 Summary of Design Considerations Little specific assistance is available to make the required decisions about design particularly since many of them are at least partially applicationdependent. However cost and overhead information such as that described earlier in this chapter performance analysis such as that described in 63 design methodologies . those described in the next sections and prototype design assistance tools . the Software Fault Tolerance Design Assistant SFTDA 87 provide valuable guidance and input to the necessary decisions. Dependable System Development Model Given the complexity of computer-based critical software the diversity of faults to be handled by these systems and the consequences and severity of their failure a systematic and structured design framework that integrates dependability concerns and requirements at the early stages of and throughout the development process is needed 88-90 . Software design faults are recognized as the current obstacle to successful dependable systems development 91 . Conventional development methods do not incorporate the processes and key activities required for effective development of dependable systems. To fill this need Kaaniche Blanquart Laprie and colleagues 91 92 developed the dependability-explicit development model. The model provides guidelines emphasizing the key issues to be addressed during the main stages of dependable systems development 91 92 . In this section we provide an overview of the development model s key activities for the fault tolerance process and refer the reader to the sources 91 92 for additional details and activities in other processes. The dependability-explicit development model provides lists of key activities related to system development phases. The requirements phase begins with a detailed description of the system s intended functions and definition of the system s dependability objectives. The .