What Is Structured Analysis?

Structured Analysis ( SA ) is a method in software engineering. Structured analysis and structured design can analyze business needs, convert them into specification files, and finally generate computer software, hardware configuration, and related manuals. And procedures.

Structured analysis and design technology is the basis of system analysis, which was developed from system analysis technology from the 1960s to the 1970s ^[1]

Chinese name: Structured analysis
Foreign name: structured analysis

Abbreviation: SA
Presentation time: Late 1970s

Structured Analysis Purpose

Structured analysis has been widely used since the 1980s. Structured analysis involves transforming system concepts into data and control representations, that is, data flow diagrams. The program in the data flow chart is represented by a bubble, so it is also called a "bubble chart". However, there may be many "bubbles" in the complete data flow diagram, making it difficult to track data movements. At this time, you can first define the events that the external system needs to respond to, and specify a bubble for each event. After the system definition is complete, connect the event bubble and the responding program bubble. Programs can also be grouped into bubbles to form higher-level programs. The data dictionary is used to describe the movement of data and instructions, and the program specifications are used to describe the relevant information of transactions or data conversion.

Many well-known analysis methods are related to structured analysis (SA) and structured design (SD), including structure diagrams, data flow diagrams and data model diagrams. Many program design methodologies also combine structured analysis and structured design, including structured systems analysis and design methods (SSADM) and structured analysis and design techniques (SADT). ^[2]

Structured Analysis History

Structured analysis is part of many structured methods. "Structured analysis is a combination of system analysis, design, and programming techniques. Its purpose is to deal with problems encountered in software development from the 1960s to the 1980s. Most of this period was developed in COBOL and Fortran languages. Later, C language and BASIC does not have the technology to document requirements and designs. As the system becomes larger and more complex, the development of information systems becomes more and more difficult. In order to facilitate the management of large and complex systems, the following have evolved Structured approach. ^[3]

Many structured methods have emerged since 1967: ^[3]

Structured Programming: Proposed by Izger Dijkstra in 1967-"GOTO Statement of Harm".
Stepwise design: proposed by Nicklaus Wilt in 1971.
The Nassi-Shneiderman diagram that appeared in 1972.
Warnier / Orr diagram presented in 1974-"Logical Construction of Programs".
HIPO-IBM Hierarchical Input-Process-Output Graph proposed in 1974.
Structured Design: Proposed by Larry Constantine, Edward Juden, and Wayne Stevens in 1975.
Jackson Structured Programming: Proposed by Michael Anthony Jackson in 1975.
Structured Analysis: Proposed by Tom Dimak and Juden, circa 1978.
Structured Analysis and Design Technology (SADT): Developed by Douglas T. Rose.
Euden Structured Approach: Proposed by Edward Euden.
Structured Analysis and System Specification: proposed by Tom Dimak in 1979.
Structured System Analysis and Design Method (SSADM): First proposed by the British Business Office in 1983.
IDEF0, based on structured analysis and design technology, was proposed by Douglas T. Rose in 1985. ^[4]
Hatley-Pirbhai model: Defined in the "Strategies for Real-Time System Specification" by Derek J. Hatley and Imtiaz A. Pirbhai in 1988.
Information Engineering: Proposed by Clive Finkelstein around the 1990s, and later widely known by James Martin.

According to the definition proposed by Hay in 1999: "Information engineering is an extension of many structured technologies proposed in the 1970s. First from structured programming to structured design, then to structured system analysis. The diagrams used for these technologies are also different : Structure diagrams are used in structured design, and data flow diagrams are used in structured system analysis. Both can help program developers and users communicate, and improve the discipline of program analysts and designers. Tools have been available since 1980. Automatically draw such drawings and track the contents of the data dictionary. "After computer-aided design and computer-aided manufacturing (CAD / CAM) terms became widely used, the use of these tools was also known as computer-aided software engineering (CASE) .

Structured Analysis Topics

Structured analysis abstraction mechanism

Structured analysis typically creates a hierarchical system using a single abstraction mechanism. Structured analysis methods can use IDEF (pictured). IDEF is a program-driven analysis method that starts from the purpose and perspective. This method will first confirm the overall function, and then repeatedly divide the function into smaller functions, retaining the inputs, outputs, controls, and mechanisms needed for program optimization. IDEF is also regarded as a functional decomposition analysis method, focusing on the cohesion of functions and the coupling between functions. ^[5]

The structured method of functional decomposition simply describes the program without delineating the behavior of the system, nor does it determine the system architecture that requires functionality. This method only confirms the inputs and outputs related to the activity. One reason structured analysis is popular is that it is inherently suitable for describing a high-level procedure and concept, even for enterprise-level procedures. However, for the common object-oriented processes commonly used in business, what functions do objects need, IDEF provides limited information. The Unified Modeling Language (UML) is the opposite of IDEF. The Unified Modeling Language is interface-driven and has multiple abstraction mechanisms, suitable for describing service-oriented architecture (SOA).

Structured analysis

Structured analysis looks at a system from the perspective of data moving in different modules, and the functions of the system can be represented by programs that transform data streams. Structured analysis makes good use of the information hiding feature of functional disassembly (or design from top to bottom), so you can focus on important details without being disturbed by irrelevant details. As the level of detail increases, so does the breadth of information. The result of structured analysis is a set of related diagrams, program descriptions, and data definitions. These data describe the data and transformations that a program needs to meet the functional requirements. ^[6]

Tom Demark's analysis includes the following: ^[7]

System diagram
Data flow chart
Program specifications
Data Dictionary

The data flow chart is a directed graph, where arcs represent data, and nodes (represented by circles or bubbles) represent programs that transform data. The program can be further subdivided into more detailed data flow diagrams, describing the subroutines in the program, until the function of the program is clearly explained and understood. Functional primitives refer to programs that do not need to be subdivided. Generally, program specifications (or micro-specifications) are used to describe them. Program specifications can include pseudo-code, flowcharts, or structured English. The data flow diagram represents the system's architecture as a network formed by many interconnected programs, and each program is composed of functional elements. A data dictionary is a set of definitions of data streams, data elements, files, and databases. The data flow chart or other data dictionary can refer to the content in the data dictionary.

Structured analysis system diagram

The system relationship diagram (System Context Diagram) represents the role between the system and the external environment. The system relationship diagram can represent the input and output of a system and related external systems.

Kossiakoff defines a system relationship diagram as "a system relationship diagram places the system in the center of the entire diagram, without describing its internal structure, and is surrounded by its related systems, activities, and environment. The purpose of the environment diagram is to focus on what affects the system External factors and events of requirements and constraints. "System diagrams and data flow diagrams ^{[8] are} relevant to help understand the relationship between the system and other related systems or events.

Structured Analysis Data Dictionary

Entity connection pattern diagrams are very important when designing a database

A data dictionary or database dictionary is a file that defines the basic organization of a database. The data dictionary includes all the files in the database, the number of fields in each file, the field names and types. In order to protect the contents of the data dictionary from being destroyed, most database management systems ^[9] do not allow users to change the data dictionary. The data dictionary has no data content in the database, only some information needed to access the database. The database management system must cooperate with the data dictionary to access the contents of the database.

Structured analysis data flow chart

A data flow diagram (DFD) is a graphical representation of the movement of data in an information system. The data flow chart is different from the system flow chart, which mainly indicates the movement of data between different programs, not the control flow of the program. The data flow diagram was proposed by Larry Constantine and is based on Martin and Estrin's "data flow graph". ^[10]

Generally, before drawing a data flow chart, an environment diagram is drawn to describe the interaction between the system and the external environment. The data flow diagram partitions the system into smaller parts and emphasizes the movement of data between the parts. The data flow diagram is one of three important diagrams of the Structured System Analysis and Design Methodology (SSADM).

Structured Analysis Structure Diagram

A structural diagram (SC) is a diagram that disassembles the system into the smallest manageable program units. ^[11] In structured programming, the structure diagram can organize the program modules into a tree structure. Each module is represented by a box with the module name. The tree structure can clearly indicate the relationship between the modules.

Structure diagrams commonly used in structured analysis represent the top-level architecture of a program. Structure diagrams help programmers deal with software problems in a smashing manner, that is, they will be broken down into smaller problems until the problem is small enough to be understood by humans. This procedure is called top-down design or functional decomposition. Structural drawings act like blueprints used in building houses. During the design phase, structure drawings are the way customers communicate with different software engineers. At the stage of code implementation, the complete architecture of the system can be known from the structure diagram.

Structured analysis

Structured design (SD) is the development of software modules and the "module hierarchy" between analysis modules. In structured design, there are two main concepts:

Cohesion refers to the degree to which functionally related programs are combined into a module.
Coupling force refers to the degree to which information or parameters move between modules.

When the coupling force is adjusted to the optimal situation, the interface between the modules is simplified, and the complexity of the program is also simplified.

Page-Jones had three topics in his research in 1980: ^[12] Structure diagrams, module specifications, and data dictionaries. "The purpose of the structure diagram is to represent the module level. Module specifications can be composed of pseudo-code or programming languages. A data dictionary is similar to a data dictionary in structured analysis. It can automatically generate data type declarations and templates for programs or subroutines. "

Structured Analysis Structured Query Language

Structured Query Language (SQL) is a standard language for querying databases. Structured query language was first used in a commercial database system, and later became the most popular database query language in database management systems operated by mini computers and large computers. Structured query language can also be used in database management systems in general personal computers, and can be used with decentralized databases, thus allowing many users to access the same database content simultaneously on the network. ^[4]