Test center analysis
In the test, under normal circumstances, it will appear in the multiple-choice questions and fill-in-the-blank questions
Frequently tested knowledge points include:
master the demand modeling method of data flow diagram (DFD),
master the DEF0 function modeling method
, understand the difference between DFD and IDF0 models
2.1 Demand Analysis
1. The concept and significance of requirements analysis
Description: A comprehensive description of what the system to be developed does and what functions it completes.
Difficulty in obtaining requirements:
complex software functions,
variability of requirements,
immutability of software products
The main task: analyze the business process of the current system clearly, including the system structure, the main tasks completed by each functional department, the relationship between each functional department and the information exchanged.
Existing problems: analyze clearly the problems existing in the current system, including the problems that need to be solved.
The final result: display in the form of models, such as DFD diagram, IDEF0 diagram and other modeling tools and methods to describe the information flow, functional structure and completion of each function of the system Required data
Basic requirements: The requirement description should be accurate, clear, and consistent, without any incomplete, ambiguous, or ambiguous descriptions.
Requirements Acquisition Method
Interview: System analysts conduct knowledge exchange with user-side experts and business personnel, talk with them, and obtain requirements.
Field observation: Observe the user's operation process on the spot. Think about how to do it more efficiently compared to the existing system.
Questionnaire survey: If too many individuals need to be interviewed and detailed questions that are easy to determine need to be answered, a questionnaire survey can be used.
Consult information: collect and consult relevant literature and information, such as organizational charts, rules and regulations, related documents, charts and reports, etc.
Requirements analysis process
A. Identifying problems: The first step of requirements analysis is to gain an understanding of all solving problems and their operating environment through problems and identification.
B. Establishing a demand model: At present, a structured analysis model or an object-oriented analysis model can be used in the demand analysis of an information system.
C. Describe requirements: requirements, functions, information, performance, environment, and other requirements.
D. Requirements confirmation: Requirements confirmation and review. Review functional requirements,
data requirements, performance, data management, and other requirements.
2.2 Demand analysis method
At present, the following methods can be used in the requirements analysis of information systems:
Structural analysis and modeling methods
such as: DFD modeling, IDEF modeling
Object-oriented analysis and modeling methods (introduced in Chapter 5)
such as: UML use case modeling
Key Benefits of the Structured Analysis and Modeling Approach
1. Don't get bogged down in the specifics too early.
2. Analyze problems from a holistic or macro perspective, such as the overall structure of the business system, the relationship between systems and subsystems.
3. Intuitively represent what the system will do and what functions it will complete through graphical model objects.
4. The graphical modeling method is convenient for system analysts to understand and describe the system.
5. The model object does not involve too many technical terms, which is convenient for users to understand the model.
DFD requirements modeling method
Basic elements of DFD method
DFD modeling method, also known as process modeling and functional modeling method, the core is data flow, starting from the data flow of the application system to graphically describe and represent the data processing process and data flow in a specific business system.
Basic element (model object) data flow of DFD method
. The data flow uses an arrow to describe the flow of data, and the content marked on the arrow can be information description or data item.
deal with. Represents the processing and transformation of data, represented by a rectangular box in the figure. The data stream that points to a process is the input data for that process, and the data stream that leaves the process is the output data for that process.
data storage. Represents data stored in the form of a database (or in the form of a file), where storage is indicated by arrows pointing to or leaving the data store, respectively.
External items (also known as data sources or data destinations). Describes the provider of system data or the consumer of data. It is represented by a rounded corner box or a parallelogram box in the figure.
DFD diagram
DFD adopts a top-down and gradually refined structured analysis method to represent the target system.
DFD modeling process
Specific modeling process and steps:
(1) Define the goal and determine the scope of the system.
Describe the user's functional requirements for the target system in a complete, accurate, and consistent manner.
(2) Establish the top-level DFD diagram.
Explain the system boundary, that is, the input and output data flow of the system, and there is only one top-level DFD.
(3) Construct the first-layer DFD decomposition diagram.
The middle layer DFD describes the decomposition of a process, and its components need to be further decomposed.
(4) Develop a DFD hierarchy diagram
Principle: maintain a uniform model depth
Select by difficulty
If a process is difficult to name exactly, consider re-decomposing it.
(5) Check and confirm the DFD diagram.
5 rules.
Check the 5 rules of the DFD diagram:
the data flow described in the parent diagram must appear in the corresponding subgraph.
A process has at least one input stream and output stream.
A storage must have incoming data flow and outgoing data flow.
At least one end of a data flow is a processing box.
The information described by the expression is comprehensive, complete, correct and consistent.
IDEFO
approach: Arrows represent data flow, rectangles represent activities.
UML method: Requirements analysis of information systems can also be carried out.