Software requirements analysis of requirements engineering

The needs analysis is summarized as:

• Decomposition of requirements : using a top-down approach (to produce an outline of software requirements specifications)
  • Take business process as the main clue: suitable for online transaction processing system, management information system, etc.
  • Take the structure of the program as the main clue: applicable to the situation where the problem domain is not complicated or the system is not strongly related to the problem domain
  • Scenario-based decomposition structure: suitable for decision support systems, user-oriented embedded systems
  • Data-based decomposition structure: suitable for data projects such as data warehouses
• Demand refinement : a bottom-up approach
  • Business item
  • Business Process
  • Every document
  • Every record
• Eliminate conflicts in the process of demand analysis and refining

Requirements modeling: (UML)

Modeling goals :

• Help the demand analyst to visualize the system according to the actual situation or according to the style of demand
• Provide a way to specify the structure or behavior of a document
• Give a template to guide system construction
• Document the decisions made by the needs analysis

Key points of modeling :

• The design should take into account the unplanned changes
• Design to be documented
• Expressing the architecture with a visual model helps understand the meaning of change

Common requirements analysis methods:

• Structured analysis (SA)
• Object-oriented analysis (OOA)
• Problem-oriented analysis (PDOA)

1. Structured analysis methods

Structured analysis: It is a data flow-oriented demand analysis method, dedicated to system-wide transaction processing, data flow, and modeling of stored data structures (similar to human thinking)

Modeling models include:

• Data flow diagram (DFD) (functional model) (Four elements: external entities, processing, data flow. Data storage)
  • Identify entities from descriptive information
  • Determine the entity identifier
  • Establish relationships between entities
  • Add detailed description information
• Data dictionary (DD) (name, alias, place of use, scope of use, description, unit / format) (can accurately define the specific meaning of each component in the data flow diagram)
  • Data stream entry
    • Data stream name
    • Explanation
    • Source of data flow
    • Data flow
    • Data stream composition
  • Data item entry
  • Data file entries
  • Data processing items
• Entity relationship diagram (ERD) (data model)

Common structured analysis techniques include:

• Data modeling
• Process modeling
• Behavior modeling
• Process, data relationship modeling
• Information Engineering Method

2. Object-oriented analysis method

    The starting point of object-oriented analysis is an original requirements document, or even a behavior specification. The true essence of OOA is to design the high-level architecture of the solution system, and it is conducive to the next development and design of the system.

Object-oriented analysis method :

• Identify the object class in the problem domain
• Define the properties and methods of these classes
• Define the behavior of these classes
• Model the relationship between these classes

Object-oriented analysis tools: (UML)

• Use case diagram
  • Basic use-case model (for modeling behavioral requirements) (constructed during requirements acquisition phase)
  • System use-case model (used to model behavior analysis) (constructed during the requirements analysis phase)
• Class Diagram
• Interactive diagram
  • Sequence diagram (sequence diagram)
  • Collaboration diagram
• Activity diagram
• Object constraint language
• State transition diagram (STD) (behavior modeling)

3. Comparison of institutionalized analysis methods and object-oriented analysis methods

Same features:

• The main model is the structural model
• Usually the focus is on modeling the solution system
• Both methods are rarely used in the field of demand acquisition
• No obvious difference between analysis and internal design

Two stages of the analysis process:

• Clarify business and process
• Identify requirements details