- process representation tool
Program flow chart: regardless of the language, it is formed by combining or nesting sequence, selection and loop structures.
IPO diagrams describe process inputs, outputs, and data processing. (Data flow diagram is also a type of IPO)
- The S graph is not suitable for complex program design and has strong structural characteristics. When the problem is complex, this graph may be very large.
Problem Analysis Diagram (PAD): structured program design with clear logical structure and standardization. (structuring, structuring, not prototyping )
Business Process Reengineering BPR: (Revolutionary Reform)
BPR is a fundamental rethinking and thorough redesign of the enterprise business .
The three levels include:
Process-centric, people-oriented, and customer-oriented .
Business process management BPM (manage):
It is a systematic approach to standardize the construction of end-to-end business process excellence and improve organizational business performance.
Process management is not a reconstruction of the existing process, but a standardized management based on the present.
The three levels include:
Standardize process, optimize process and reengineer process .
- system design
System design method:
Structured design methods and object-oriented design methods.
The main contents are outline design and detailed design.
Outline design: design the overall structure of the system, and determine the relationship between modules. Form a software module structure diagram, that is, a system structure diagram.
Detailed design: detailed algorithm, database physical design, code input and output, and writing detailed instructions.
Basic principles of system design:
Abstraction; top-down, step-by-step refinement; information concealment; module independence (high cohesion and low coupling).
Information hiding means encapsulation.
System Design Principles:
Keep the size of the module moderate, reduce the call depth as much as possible, have more fan-in and less fan-out, single entry and single exit, the scope of the module is within the module, and the function should be predictable.
More fan-in, less fan-out: It means that others call me more, and I call others less. (meaning great value, high reuse value)
Coupling and cohesion, the relationship between modules and modules is coupling, so the lower the coupling, the better. High cohesion is inside the module, and the closer the internal function points, the better.
Cohesion is as follows :
Casual cohesion: A module has no relationship between itself. (no direct relationship)
Logical cohesion: Several logically similar functions are executed within the module, and the function of the module is confirmed through parameters. (Similar logic, determined by parameters)
Temporal aggregation: Simultaneous executions are grouped together.
Process cohesion: execute in the specified process order. ( process sequence )
Communication cohesion: All elements in the module operate on a data structure with the same input and output. (same data structure operation)
Sequential cohesion: sequential execution, the output of the previous is the input of the next . (input is next output)
Functional cohesion: To complete a function together, both are indispensable. (Common cohesion, both are indispensable)
The coupling is as follows :
No direct coupling: There is no relationship between the two modules.
Data coupling: There is a call relationship between two modules, and data values are passed.
Tag coupling: Two modules pass data structures.
Control coupling: One module calls another module, transfers control variables, and determines a certain function through variables. (Control a certain function through variables)
External coupling: The module inputs and outputs through an environment other than the software, such as I/O. (software external environment)
Common coupling: a common data environment. (public data structure)
Content coupling: When a module directly uses the internal data of another module, or transfers to another module through an abnormal entry.