Structured analysis is a set of techniques and graphical tools that allow the analyst to develop a new kind of system specifications that are easily understandable to the user. Analysts work primarily with their wits, pencil, and paper. Most of them have no tools. The traditional approach focuses on cost/benefit and feasibility analyses, project management, hardware and software selection, and personnel considerations. In contrast, structured analysis considers new goals and structured tools for analysis. The new goals specify the following:
1.Use graphic: wherever possible to help communicate better with the user.
2.Differentiate between logical and physical systems.
3.Build a logical system model to familiarize the user with system characteristics and interrelationships before implementation.
The structured tools focus on the tools listed earlier essentially the data flow diagram, data dictionary, structured English, decision trees, and decision tables. The objective is to build a new document, called system specifications. This document provides the basis for design and implementation. The primary steps are:
- Study affected user areas, resulting in a physical DFD. The logical equivalent of the present system results in a logical DFD.
- Remove the physical checkpoints and replace them with a logical equivalent, resulting in the logical DFD.
Source: Adapted from Tom De Marco, Structured Analysis and System Specifications (New York: Yourdon Press. 19791. p. 26.
- Model new logical system. So far no consideration is given to modifying methods called for in the feasibility report. This step incorporates the changes and begins to describe the candidate system. It is essentially a paper model system to be installed.
- Establish man/machine interface. This process modifies the logical DFD for the candidate system and" considers the hardware needed to implement the system. The collaboration results in the physical DFD of the candidate system.
- Quantify costs and benefits and select hardware.
The purpose of this step is to cost justify the system, leading to the selection of hardware for the candidate system. All that is left after this step is writing the structured specification.
The structured specification consists of the DFDs that show the najor' decomposition of system functions and their interfaces, the data dictionary documenting all interlace flows and data stores on the DFDs, and documentation of the intervals of DFDs in a rigorous manner through structured English, decision trees, and decision tables.
In summary, structured analysis has the following attributes:
1.It is graphic. The DFD, for example, presents a picture of what is being specified and is a conceptually easy-to-understand presentation of the application.
2.The process is partitioned so that we have a clear picture of the progression from general to specific in the system flow.
3.It is logical rather than physical. The elements of system do not depend on vendor or hardware. They specify in a precise, concise, and highly readable manner the workings of the system and how it hangs together.
4.It calls for a rigorous study of the user area, a commitment that is often taken lightly in the traditional approach to systems analysis.
5 Certain tasks that are normally carried out late in the system development life cycle are moved to the analysis phase. For example, user procedures are documented during analysis rather than later in implementation.
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