Modules included in the structure diagram
1. Incoming module, 2 outgoing module, 3 transformation module, 4 coordination module
System structure diagram classification
1. Transformation system structure diagram
The process of dealing with the problem is divided into three parts: 1. Obtain the data, 2. Transform the data 3. Give the data
Transformation analysis
Process : Four-step composition
1. Redraw the data flow diagram
2. Distinguish valid (logical) input, valid (logical) output and central transformation part
3. Perform a first-level decomposition and design upper-level modules
4. Perform two-level decomposition, design the middle and lower modules of the input, output and central transformation parts
Precautions:
1. When selecting the order of module design, all direct subordinate modules of a module must be designed.
2. When designing the lower-level modules, the coupling and cohesion of the modules should be considered.
3. Use the "black box" technology: when designing the current module, first define all lower modules of this module as a "black box".
4. When the modules are divided, the direct subordinate modules of a module are generally about five.
5. If the following situations occur, stop the functional decomposition of the module.
1. When the module can no longer be subdivided into obvious subtasks
2 When decomposed into user-supplied modules or subroutines of the library
3. When the interface of the module is the information transmitted by the input and output devices
4. When the module should not be decomposed too small
2. Transactional system structure diagram
Features : Receive a transaction, select an appropriate processing unit according to the characteristics and nature of the transaction, and then give the result.
Transaction analysis
Like transformation analysis, transaction analysis starts from analyzing the data flow diagram, and then gradually decomposes it from top to bottom to establish a structure diagram of the system.
process
1. Identify the source of the transaction
2. Prescribe proper transactional structure
3. Identify various transactions and their defined operations
4. Pay attention to the use of common modules
5. Establish a transaction processing module for every thing, or a group of transactions that are closely practiced
6. Specify all their lower-level operation modules for transaction processing modules
7. Specify all the detailed modules for the operation modules