Software Engineering Chapter Three Knowledge Point summary _ software project

1. Requirements Analysis Overview: Requirements analysis is the last phase of the software definition period, its basic task is to accurately answer the "system must do" this question.

2. A clear system of integrated requirements: (1) Functional Requirements: Specify the services that the system must provide (2) performance requirements: Response time, concurrency/Extensibility (3) Reliability and availability requirements: quantitative, timed (4) Error handling Requirements "error handling" refers to actions taken when the application system finds itself committing a mistake (5) interface requirements: User, software, communications, IO (6) Constraints: Related standards, security, precision, platform (7) Reverse demand: unwanted requirements (8) possible future demand

3. Analysis System Data requirements: ER model

4. Logical model: DFD DD er graph function Structure diagram algorithm

5. Communicate with users to obtain the required methods:

(1) Interview Questionnaire scenario analysis techniques

(2) Oriented data flow Top-down refinement

(3) Simple Application Specification technology: First, preliminary interviews, through the user's answer to the basic questions, preliminary determination of the scope of the problem to be resolved and solutions. Then developers and users write "Product requirements" separately.

(4) Quickly build software prototypes: The goal of rapid prototyping is to provide users with a model of a target system that can be run on a computer as soon as possible, so that users and developers reach a consensus on what the target system should do.

6. Data objects: The abstraction of composite information that must be understood by the software. Compound information refers to things that have a series of different properties or attributes, and things that have only a single value (for example, width) are not data objects.

Data objects are associated with each other 1:1 1:n m:n

7. Note that links also have attributes

8. Paradigm

(1) First normal form each attribute value must be an atomic value, that is, a simple value without the internal structure

(2) The second normal form satisfies the condition of the first normal form, and each keyword attribute is determined by the whole keyword (and not by a part of the keyword) in violation of {school number, name, course name, grade}, where the course name cannot be determined entirely by the school number

(3) Third paradigm: conditions that conform to the second normal form, each non-primary key attribute is determined only by the keyword, and each keyword attribute cannot be merely a further description of another keyword (that is, each non-key attribute does not depend on another key attribute value) in violation of {school number, name, date of birth, age} of which age and date of birth

9. Methods of verifying software requirements:

(1) Verification of the consistency of requirements: concept consistent

(2) Verification of the reality of demand: technical

(3) Verify the integrity and effectiveness of the requirements