This column is the blogger's personal notes, the main purpose is to use the fragmented time to memorize the knowledge points of soft engineering, hereby declare!
Article directory
1. What is the purpose of the feasibility study?
2. What is the essence of the feasibility study?
3. From what aspects do you study the solution feasibility of the logic model?
4. What is the most fundamental task of feasibility study?
5. What is the proportion of the feasibility study cost to the total expected project cost?
6. What are the steps of the feasibility study?
7. What is the basic idea and function of the system flow chart?
8. When faced with a complex system, what method is generally used to describe the system?
9. What is a Data Flow Diagram (DFD)?
11. What are the 4 components of a data flow graph?
12. What is the principle of data flow diagram layering?
13. What is the purpose of data flow diagram?
14. What is a data dictionary?
15. Why are data flow diagrams and data dictionaries indispensable to form a system logic model?
16. The data dictionary consists of the definition of which 4 types of elements?
17. What is the purpose of the data dictionary?
18. What are the concepts and advantages of the MVC pattern?
19. What are the B/S architecture and the C/S architecture?
Summary at the end of the chapter
1. What is the purpose of the feasibility study?
Determine whether the problem can be solved in the shortest possible time with the least cost
2. What is the essence of the feasibility study?
Feasibility study is essentially greatly compressed and simplified system analysis and design process, that is, a system analysis and design process carried out in a relatively abstract manner at a higher abstraction level .
3. From what aspects do you study the solution feasibility of the logic model?
- technical feasibility
- economic feasibility
- operational feasibility
- social feasibility
4. What is the most fundamental task of feasibility study?
Make recommendations for a future course of action
5. What is the proportion of the feasibility study cost to the total expected project cost?
5%~10%
6. What are the steps of the feasibility study?
- Review system size and goals
- Research systems currently in use
- Deriving the high-level logical structure of the new system: that is, from the existing physical system --> the existing system logical model --> the target system logical model --> the target physical system
- further define the problem
- Deriving and evaluating alternative solutions
- recommended course of action
- draft development plan
- Write a document and submit it for review
7. What is the basic idea and function of the system flow chart?
The basic idea of a system flowchart is to use graphical symbols to describe each component (program, document, database, human process, etc.) that makes up the system in the form of a black box .
The function of the system flow chart is to understand and analyze the existing system. It is a traditional tool for describing the physical system in a general way. It expresses the flow of data among the various components of the system , rather than the control process for processing the data.
8. When faced with a complex system, what method is generally used to describe the system?
layered
9. What is a Data Flow Diagram (DFD)?
Data Flow Diagram (DFD) is a graphical technique that only describes the logical process of data flowing and being processed in the software . The data flow in the data flow diagram is essentially different from the control flow represented by the arrow in the program flow chart. .
10. What are the similarities and differences between data storage and data flow in the data flow diagram?
Both data storage and data flow are data, but in different states . Data storage is data at rest , while data streaming is data in motion .
11. What are the 4 components of a data flow graph?
source or destination, processing, data storage, data flow
12. What is the principle of data flow diagram layering?
- The layering of the data flow graph must ensure the continuity of information . That is, when decomposing a process into a series of processes, the input and output data streams before and after decomposition must be the same
- The appropriate number of processing in a data flow diagram is 5~9
[Note] The naming order of the data flow graph is top layer, layer 0, and layer 1. If the graph is more complicated, you can mark the serial numbers on the processing of layer 0 and layer 1 , as shown in the following figure:
13. What is the purpose of data flow diagram?
- Can be used as a tool for exchanging information. Because dataflow diagrams use only four basic notations and contain no details of physical implementation, they can be understood and evaluated by most users
- Can be used as a tool for analysis and design. The basis of the data flow-oriented design method is the data flow diagram
14. What is a data dictionary?
A data dictionary is a collection of information about data , that is, a collection of definitions for all elements contained in a data flow diagram .
15. Why are data flow diagrams and data dictionaries indispensable to form a system logic model?
Because the data flow graph and the data fields together form the logical model of the system. Without the data dictionary, the data flow diagram is not strict ; without the data flow diagram, the data dictionary is also difficult to play a role .
16. The data dictionary consists of the definition of which 4 types of elements?
- data flow
- stream component
- data storage
- deal with
17. What is the purpose of the data dictionary?
- as a tool in the analysis phase
- Helps improve communication between analysts and users
- Helps improve communication between different developers or different development groups
- Contains valuable control information for each data element
- The data dictionary is the first step in developing a database
18. What are the concepts and advantages of the MVC pattern?
The full name of MVC is Model View Controller , which is the abbreviation of Model (Model)-View (View)-Controller (Controller) . It is a model of software design. It uses a method of separating business logic, data and interface display to organize code . Gather business logic into one component, while improving and customizing the interface and user interaction, there is no need to rewrite the business logic.
The advantage is that it can handle many different views for the application . In fact, no real processing occurs in the view, whether the data is stored online or a list of employees, as a view, it is just a way to output data and allow users to manipulate it.
19. What are the B/S architecture and the C/S architecture?
B/S architecture, the full name is Browser/Server, that is, browser and server architecture mode. Under this framework, the user's work interface is implemented through a browser, and different server-side programs can be accessed by visiting different web addresses (URLs).
C/S architecture, the full name is Client/Server, that is, client and server architecture mode. In this architecture, the user sends a network request by using a local client program, and a remote server program responds to the request and processes it.
[Note] For details, see the article I wrote below: Introduction to the basics of Web development
20. What is the relationship between a scenario and a state diagram that describes all possible sequences of actions?
A scenario is just a path through part or all of the state diagram , that is, the scenario only describes a typical behavior of the system ; while the state diagram describes all the behavior of the system , so the state diagram contains the scenario.
[Note] As shown in the state diagram of the telephone system below, dialing is only a scenario, and it is a typical behavior of the telephone system
21. Why does the data flow graph not have relevant rules about the reachability between nodes like the program flow chart?
Because dataflow diagrams do not describe control , there may be no path between two "processes" in a dataflow diagram . If each process uses different input data and generates different output data, and the output of one process is not used as input for another process , then there is no arc between them.
Summary at the end of the chapter
A feasibility study further explores whether there is a feasible solution to the problem identified in the problem definition phase . On the basis of correct
definition of the problem, by analyzing the problem (often need to study the system currently in use), derive a tentative solution , then
review and revise the problem definition, analyze the problem again to improve the proposed solution ... Through
the iterative process of defining the problem, analyzing the problem , and proposing a solution, a high-level logical model that meets the system goal is finally proposed .
Then imagine various possible physical systems according to this logical model of the system , and analyze
the feasibility of these physical systems from various aspects such as technology, economy and operation. Finally, the systems analyst proposes a recommended course of action for
review and approval by the heads of the user and client organization. A system flowchart is an excellent tool
for expressing an analyst's perception of an existing system and for describing his vision of a future physical system . A system flow diagram is essentially a physical data flow diagram that depicts the main physical elements that make up a system and how information flows and is processed among these elements . There are only four basic symbols in data flow diagram, which is an excellent tool to describe the logical model of the system . Usually the data dictionary and the data flow diagram together constitute the logical model of the system. Without a data dictionary that precisely defines each element in the data flow diagram, the data flow diagram is not rigorous enough
; However, without a data flow diagram, the data dictionary is also difficult to play a role , and the two are indispensable.
Cost/benefit analysis is an important part of the feasibility study, and it is the main basis for the head of the client organization to judge whether to
continue investing in the project from an economic point of view.
Readers should re-understand the necessity of feasibility study , as well as its basic tasks and basic steps. On this basis,
further study specific methods and tools. An in-depth understanding of specific methods and tools can in turn deepen
the understanding of the feasibility study process. However, don't get bogged down in the details of specific methods and tools and neglect to
learn the basic principles and concepts of software engineering.
Next chapter: Software Engineering——Chapter 3 Requirements Analysis Knowledge Points Arrangement
Repeatedly, down-to-earth; never forgetting, there will be echoes!