Modern Structured Analysis Online Reading Notes 3-structured analysis tools

At the beginning, the author explains why modeling is required. Next, he describes four key structural analysis model tools, which are well-known.DFD(Dataflow digoal),ERD (entity relationship digoal),STD(State Transition Divisor),SC (structure chart)

 

The following is a simple description.

1. DFD (dataflow digoal)

 

DFD diagram is used to describe the data processing process. Includes: data stream, data storage, processing (function), external entity, output (this symbol indicates that the final external entity or user output cannot be determined)

Because the structured analysis system does not ultimately unify the metasigned system, we can see that some customers use different symbolic systems.

By analyzing the requirement document, we can form a hierarchical DFD. The first layer is dfd0. By further breaking down a function in dfd0, we can see that the second layer is dfd1, and so on, you can get dfd2 ......

According to the requirements of the current system analysis, we should analyze the external behaviors of a system for its environment. By combining these behaviors, we can obtain dfd0, then, we can analyze the further implementation of these behaviors to obtain dfd1 and so on.

 

Along with DFD, two important documents are data dictionary and functional specifications.

Since DFD has hierarchical features, the above documents should also be easy to use.

2. ERD (entity releationship digoal)

 

 

Since the birth of ERD, it has been favored by system analysts. Since then, ERD has become more expressive than 20 years ago.

3. STD (state transition dition)

 

 

The state transition diagram is used to analyze the state changes of an object after being triggered by an event. In some systems, creating a state chart of an object can help you better understand its behavior. In real-time systems, the state transition diagram is widely used. We can use the state and action matrix relationships to control the state transition.

 

In an object-oriented system, state diagrams are used to track the state changes of an object. Its function is similar to the expression method and the state transition diagram.

 

4. SC (structure chart)

How modules in the system should be organized, how to call each other, what parameters should be passed, and how the hierarchy is formed.

 

 

 

These four images are still quite active. In the object-oriented analysis design system, the corresponding graphs are also prepared for the four graphs.

The key is that the author not only puts forward four types of graphs, but more importantly, points out that as a system model, these four graphs can be organized hierarchically at an appropriate organizational level, the system architecture can be obtained.