The core content of the third chapter of the Introduction to software engineering

Tasks in the Software requirements Analysis phase: requirements acquisition, requirements analysis, requirements definition, and requirements validation.  Structured Analysis Method: A method of demand analysis oriented to data flow. Classification of structured design methods: A class is designed according to the data flow of the system, called data flow-oriented design, or process-driven design, and the other is designed according to the data structure of the system, referred to as the design of data-oriented structure, or the design that is designed by the drive.  Demand acquisition is a decisive step in software survival, involving customers, users, and developers. The problem of demand acquisition: The goal or scope of the system, the problem of the inaccuracy of demand, the need for the variable problem of demand to acquire the task: to identify and analyze the problem, and to analyze the relationship between the cause and result of the problem, communicate with the users in various ways, and use the research method to collect information,  According to the data process and interface to observe the different aspects of the problem, the acquisition of the requirements documented, in the form of use cases, decision tables, decision trees and so on.  Requirements to obtain the principle: in layman's, flow-based lines. Requirements acquisition Process: Develop high-level business models, define project scope and high-level requirements, identify user classes and user representatives, obtain specific requirements, identify business workflows for target systems, demand consolidation and summarization (functional requirements, performance requirements, environmental requirements, reliability requirements, security requirements, user interface requirements,  Resource usage requirements, software cost consumption, and development progress requirements).  Get specific requirements: communicate with users, descriptive documentation of existing or competing products, system requirements specification, current system problem reporting and improvement requirements, market research and user surveys, and observe how users work.  Tasks in the Software requirements Analysis phase: Requirements acquisition, demand analysis (completeness, correctness, rationality, feasibility, adequacy), requirements definition, requirements validation. Data dictionary: Defines the characteristics of data objects and control information in data models, functional models, and behavioral models in terms of entries, and gives their exact definitions including data flow, processing, data files, data elements, and data source points and data sinks. The data dictionary precisely and strictly defines each system-related data element. 、

The core content of the third chapter of the Introduction to software engineering