Structured Analysis Development Method

In analyzing a system, the analyst collects relatively unstructured data through interviews, questionnaires, observations procedures manuals, etc. It is essential to structure this data for systematic location of  information, reduce redundancy and have complete understanding of logical requirements.

Structured analysis is a set of techniques and graphical tools that allow the analyst to develop a new kind of system specifications and that are easily understandable to the user. Its builds process models, called data flow diagrams, for a system. It focuses on what the system or application does rather than on how it is done (i.e., emphasis is logical, not physical) and it uses graphic symbols to describe movement and processing of data.

Data Flow Diagrams

All information systems process data to produce information and maintain stored data. A data flow diagram (DFD) is the tool used to depict the data flow model diagrammatically. It shows the over all flow through a system and the work performed by the system. A DFD is also known as a "bubble chart" consist of a series of bubbles joined by lines. The bubbles represent data transformations and the lines represent data flows in the system.

Data flow diagram construction - a checklist

a) Attempt to grasp central principles.

b) Identify sinks and sources. This will both provide system boundaries and identify a set of dataflows related to the sinks and sources.

c) Starting with this input from a sources or output to a sink, place a box where a process is required to transform the data flow. Review the data needs of the process, and, accordingly identify additional data items.

d) Accept the need to re-draft the diagram several times.

e) Follow a typical transaction through the system, modeling the logical activities that affect it.

f) Remember that most process access a store of some kind.

g) Do not strive for absolute correctness. There is often more than one way to draw a DFD.