Soft work Video Summary Part Three

Software Requirements Analysis

Task

solve the target system "what" problem

In-depth description of software functionality and performance

Determine the constraints and software interfaces involved in the software

Other effective requirements for top-easy software

Characteristics

Consistency, completeness, time-limited, validity, verifiable

The process of demand analysis

Problem identification

The communication pathways needed to establish the analysis

analysis and synthesis

From the information flow and structure, gradually refine all the software functions, find out the connection, interface characteristics and design constraints, analyze whether they meet the functional requirements, whether reasonable

Prepare documentation for the requirements analysis phase

Software Requirements Specification

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Data requirements Specification

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preliminary user manual

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Modify the evening with the Deterministic Software development implementation Plan

review

system-defined targets are consistent with user requirements

Complete documentation provided in the system requirements analysis phase

All the descriptions in the document are complete, clear, and accurately reflect the needs of the user

important interfaces with all other system components are already described in

soft Method of requirements Analysis

SA: A structured analysis method for data flow

JSD: Jackson method for data structure

DSSD; method of developing structured data systems

ooa: Object-oriented parsing method

The principle of software requirement analysis

decomposition, simplification and abstraction

Abstract

understand the problem before you start building an analytic model

Development Model

documenting the origins and causes of demand

using the requirements View

give priority to demand

Remove exclusions

Decomposition

vertical decomposition and lateral decomposition

Streaming Diagram (DFD)

features

Abstraction, generality, hierarchy

Main graphic elements

The relationship between data flow and data processing

guidelines for checking and modifying DFD

there can be only four graphic elements

at least one input data stream and one output data stream per processing

The main diagram of the streaming diagram must consist of four basic elements, indispensable

need to add number

the sub-diagram corresponds to the main diagram

Each element must have a name, and no control flow is allowed

The role of the streaming diagram

system analyst can use it to customize down the system Information flow

you can draw a section of the graph that requires computer processing

based on data storage, further analysis of data, like the database design over

according to the direction of data flow, set the access mode

corresponding to a processing process, with the corresponding language, Judgment table and other tools to express processing methods

Advantages and disadvantages of DFD

The

overall concept is strong, each layer emphasizes "what to do, what to need, what to give"

can reflect the flow of data and the processing process

self-defined downward analysis, easy to find the system parts of the logic error, easy to correct

easy to compare with computer processing

not intuitive, need to generalize, abstract, correct

No computer, manual drawing too cumbersome, heavy workload

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Soft Work Video summary Part three