How many steps are there in the overall design? specifically is?
The overall design process usually consists of two main stages:
In the system design stage, determine the specific implementation plan of the system; in the structure design stage, determine the software structure. The typical overall design process includes the following 9 steps.
Imagine alternatives
In the overall design stage, the analyst should consider various possible implementation schemes and strive to choose the best scheme from them. A common method of conceiving alternative solutions is to conceive of the various possible methods of processing grouping in the data flow diagram, and discarding the grouping methods that are technically impractical. The remaining grouping methods represent possible implementation strategies and can be Reveal alternative physical systems.
Choose a reasonable plan
A number of reasonable solutions should be selected from a series of alternative solutions obtained in the previous step, usually at least three solutions of low cost, medium cost and high cost should be selected. When judging which solutions are reasonable, one should consider the project scale and goals determined in the problem definition and feasibility study stage, and sometimes it may be necessary to further solicit the opinions of users.
Recommend the best solution
The analyst should comprehensively analyze and compare the pros and cons of various reasonable solutions, recommend the best solution, and specify a detailed implementation plan for the recommended solution.
Functional decomposition
In order to finally realize the target system, it is necessary to design all the programs and files (or databases) that make up the system. The design of the program (especially the complex large-scale program) is usually divided into two stages: first, the structure design, and then the process design. The structure design determines which modules the program consists of and the relationship between these modules; the process design determines the processing process of each module. The result design is the task of the overall design stage, and the process design is the task of the detailed design stage.
Design software structure
Usually a module in the program completes an appropriate sub-function. Modules should be organized into a good hierarchical system. The top-level module calls its lower-level modules to achieve the complete function of the program, and each lower-level module calls the lower-level modules to complete a sub-function of the program, and the lowest-level module completes the most specific Function. The software structure (that is, a hierarchical system composed of modules) can be described by a hierarchical diagram or a structure diagram.
Design database
For those application systems that need to use the database, software engineers should further design the database on the basis of the system data requirements determined in the requirements analysis stage.
Develop a test plan
Considering testing issues in the early stages of software development can encourage software designers to pay attention to improving the testability of the software when designing.
Write a document
Formal documents should be used to record the results of the overall design. The documents that should be completed at this stage are usually the following: system description, user manual, test plan, detailed implementation plan, and database design results.
Review and review
Finally, a strict technical review should be carried out on the results of the overall design, and after the technical review is passed, the customer should review it from a management perspective.
2. What are the two design components of the overall design? What is the difference between the two?
The overall design stage is mainly composed of two stages: system design and structural design. System design stage: Determine the specific implementation plan of the system. Structure design stage: Determine the software structure.
3. How many kinds of coupling are mentioned in the design principle? How many kinds of cohesion are there? What are they?
Coupling can be divided into the following seven types, and the degree of coupling between them is arranged from high to low as follows: content coupling, common coupling, external coupling, control coupling, tag coupling, data coupling, and indirect coupling.
There are seven types of cohesion, and the cohesion between them is arranged from weak to strong as follows: accidental cohesion, logical cohesion, time cohesion, medium cohesion (process cohesion, communication cohesion), high cohesion ( Sequence cohesion, function cohesion).
4. Which coupling should be avoided in the design principle?
Try to use data coupling, use less control coupling and feature coupling, limit the scope of public environment coupling, and don't use content coupling at all.