- The original author of this article: Brother Gu’s younger brother
- Author blog address: http://blog.csdn.net/lfdfhl
- Reference materials for this article: "Software Documentation Writing Tutorial" by Electronic Industry Press, edited by Ma Ping and Huang Dongmei
Overview of the outline design book
The "Summary Design Manual" is also called the "System Design Manual". Structural design and error handling design, etc., provide the basis for the detailed design of the program.
Outline Design Book Compilation Objectives
In the stage of software requirements analysis, the software "what to do" has been clarified, and these requirements are described through the specification, which is also the logical model of the target system. Entering the design stage, it is necessary to transform the logical model of the software "what to do" into a physical model of "how to do it", that is, start to realize the requirements of the software, and reflect the design results in the "design specification" document, so the software design It is a process of converting software requirements into software representation. Initially, this representation only describes the overall architecture of the software, which is called software outline design or structural design.
The basic tasks of outline design include the following aspects.
Design software system structure
In order to realize the target system, all the programs and databases (files) that make up the system must be designed. For the program, the structural design is carried out first, specifically: (a) Using a certain design method to divide a complex system by
function into modules.
(b) Determine the function of each module.
© Determine the calling relationship between modules.
(d) Determine the interface between the modules, that is, the information passed between the modules.
(e) Evaluate the quality of the module structure.
According to the above content, the design of the software structure is based on the module, and the system has been divided into a hierarchical structure in the requirement analysis stage. In the design phase, based on the results of the requirements analysis, it is further divided into modules from the perspective of realization, and forms a hierarchical structure of modules. The design of the software structure is a key step in the general design, which directly affects the detailed design and coding work in the next stage. The quality and some overall characteristics of the software system are determined in the design of the software structure.
Data structure and database design
For software systems for large-scale data processing, in addition to the module design of the control structure, the data structure and database design are also very important.
(a) Design of data structure
The method of gradual refinement is also applicable to the design of data structure. In the requirements analysis stage, the data composition, operation constraints, and the relationship between data have been described through the data dictionary, and the structural characteristics of the data have been determined. implementation details. In the outline design stage, abstract data types should be used.
(b) Database design
Database design refers to the design of data storage files, mainly in the following aspects:
①Conceptual design
is based on data analysis, using a bottom-up approach to view design from the user's perspective, generally using ER model to represent the data model, which is a conceptual model.
②Logical design
ER model or IDEFlx model is independent of the database management system (DBMS), and the logical structure of the database should be established in combination with specific DBMS features. For specification, it is necessary to give the definition of the data structure, that is, to define the contained data items, types, lengths and tables of levels or relationships between them, etc.
③Physical design
For different DBMSs, the physical environment is different, and the storage structure and access methods provided are different. Physical design is to design some physical details of the data model, such as data item storage requirements, access methods, and index establishment.
Write a high-level design document
Documents mainly include:
(a) Outline design specification.
(b) Database design specification, which mainly gives the introduction of the DBMS used, the conceptual model of the database, logical design, and results.
© User Manual, supplementing the user manual written during the requirements analysis phase.
(d) Revise the test plan and put forward clear requirements for test strategies, methods and steps.
review
Whether the design part fully realizes the functions and performance requirements stipulated in the requirements, the feasibility of the design scheme, the key processing and the correctness and effectiveness of the definition of internal and external interfaces, and the consistency between each part are all carried out. review.
Outline design is an important link in software development, which determines the direction and process of software development. Because software development is a complex process that needs to consider all aspects of content, if there is no programmatic document to organize and manage, then software development must be a mess. Therefore, the outline design book provoked this important task.
Summarize
The outline design book we write should achieve the following four goals.
1. Determine the development plan
If ten people are allowed to carry out software development directly with a requirement analysis book, the final result is likely to develop ten systems with different styles and the same functions. Although these systems have the same function, their implementation methods have their own advantages and disadvantages. By comparing with each other, we can know which one is better and which one is worse. But for software development, it is impossible for us to develop ten software at the same time and let customers choose one to use, which is a waste of time and money. Therefore, the development plan must be determined after in-depth investigation, overall consideration and detailed comparison in the general design stage of software development.
2. Describe the overall picture of the software
Since the outline design is to design the software at the macro level, determine the system architecture, system module division and technical route adopted, and point out the key technical difficulties in realizing the system. Therefore, in the outline design book, it focuses on recording the operating environment of the software, the division of functional modules and their interrelationships, and does not involve the implementation details of the functions.
3. Enabling the shift from customers to software developers
In the early stage of software system development, generally only a few senior system analysts contact customers to understand requirements, form requirements analysis documents, and then return to the software company to do outline design. The outline design and the following stages are all carried out by software practitioners. These software practitioners have the same domain knowledge, and it is sometimes easier to express and understand the problem in professional terms than in natural language, and It is not easy to have ambiguity. The outline design document acts as a bridge between customers and software practitioners, transforming the requirements described by customers in natural language into system function specifications that software practitioners can easily understand.
4. Provide machinable materials for the detailed design stage
All detailed designs are based on the modules and components divided in the general design, and must abide by the principles of the general design. Therefore, the outline design is the material, basis, and standard of the detailed design, and it is the starting point for the detailed design work.