Structured Analysis (SA)

1. What do you call a model? I think it's keyword: abstract important features reduce complexity.

2. Methods of Software Design

Category: Feature-oriented, object-oriented design.

The data flow oriented approach is mentioned in structured analysis. Oh ~

3. Structured analysis for Data flow

Features: From top to bottom (whole to local), decomposition by layer.

It involves a streaming diagram (DFD)

#DFD是什么? Describe the flow and process of data between each logical function module.

#DFD的构成及符号: Data flow (noun or noun phrase), processing (verb phrase, multi-numbered), data storage (more nouns), external entities (non-system members, more noun phrases).

#DFD的层次性

The streaming diagram is divided into top-level streaming diagrams, middle-tier streaming diagrams and underlying streaming.

Top-level DFD: An association diagram that represents the relationship of an external entity to a system, with input and output, numbered 0, whose disadvantage is that it does not reflect the order of the data. Attention! data storage cannot be placed on the top level .

0- Tier DFD: A system of top-level DFD is decomposed into several subsystems numbered 1,2......N.

Bottom of the DFD: for each subsystem in the 0-layer DFD to decompose the processing, the most bottom of the DFD in the processing called "Basic Processing", Number 1 layer: 1.1,1.2......,2 layer: 1.1.1,1.1,2 ...; 1.2.1,1.2.2 ........

A range diagram is the most abstract data flow representation of the system, which represents the entire system as a single bubble, also known as a level 0 DFD. (oh Oh ~ Clear)

Detailed explanation can be seen:http://blog.chinaunix.net/uid-21411227-id-1826829.html

Http://www.educity.cn/zk/rjgc/200608311656531370.htm

#DFD有数据平衡原则, that is, the total input and output will not change at any level.

#画流程图的步骤

1, understand the problem description.

2. Analyze the problem description and extract 4 kinds of components of the flow chart.

3, draw the top layer flow chart, that is, the basic model of the system.

4, the basic model refinement, draw all levels of detailed streaming chart.

5, Data balance principle: Check whether the hierarchical refinement of the continuity of information, that is, when a processing decomposition into a series of processing, before and after decomposition of the input and output data flow must be the same.

I should pay attention to the place: Data Flow can't flow between external entities!

Processing through the data storage to communicate, should avoid from one processing process directly to another process.

#能看懂步骤, but there are still problems with practice.

Structured Analysis (SA)