tailieunhanh - Software Engineering A PRACTITIONER’S APPROACH phần 5

(1) thiết lập một quy mô phản ánh khả năng nhận thức của một rủi ro, (2) khoanh định các hậu quả rủi ro, (3) ước tính tác động của nguy cơ về dự án và sản phẩm, và (4) lưu ý về tính chính xác của dự báo rủi ro tổng thể để sẽ không có sự hiểu lầm. | CHAPTER 12 ANALYSIS MODELING 329 CASE Tools Structured Analysis Content description a notation for representing content. Supplementary information other information about data types preset values if known restrictions or limitations and so forth. Once a data object or control item name and its aliases are entered into the data dictionary consistency in naming can be enforced. That is if an analysis team member decides to name a newly derived data item xyz but xyz is already in the dictionary the CASE tool supporting the dictionary posts a warning to indicate duplicate names. This improves the consistency of the analysis model and helps to reduce errors. Where-used how-used information is recorded automatically from the flow models. When a dictionary entry is created the CASE tool scans DFDs and CFDs to determine which processes use the data or control information and how it is used. Although this may appear unimportant it is actually one of the most important benefits of the dictionary. During analysis there is an almost continuous stream of changes. For large projects it is often quite difficult to determine the impact of a change. Many a software engineer has asked Where is this data object used What else will have to change if we modify it What will the overall impact of the change be Because the data dictionary can be treated as a database the analyst can ask where used how used questions and get answers to these queries. The notation used to develop a content description is noted in the following table Data Construct Notation Meaning is composed of Sequence and Selection I either-or Repetition 1 in n repetitions of optional data . delimits comments The notation enables a software engineer to represent composite data in one of the three fundamental ways that it can be constructed 1. As a sequence of data items. 2. As a selection from among a set of data items. 3. As a repeated grouping of data items. Each data item entry that is represented as part of a .