Entity Relationship System

Using a notation that is proper to the method of structuralized analysis, we create models that portray the flow and the content of the information (given and it has controlled), we divide the system in functional partitions and behaviors and describe the essence of what it must be constructed. The objective of this analysis is to decide the difficulties in a systematic boarding, to develop the analysis and to produce a specification of new and improved system. To obtain this objective, the structuralized analysis is centered in a clear communication. The structuralized analysis used duty to be only for simple small problems e. Although informal and it is not validated by computation, the diagram of flow of data is the part most important of the structuralized analysis. It is of well easy use. It can be used for the determination of the basic components of processing and the flows of data of a system.

It can be folloied by a more formal modeling of data. For bigger and more complex systems, the diagramming of flows of data can be used to sketch one vision of high level of the system. However, beyond this point, other methods of more rigorous analysis and specification must be used to develop a specification necessary and validated by computation. The same author affirms that the structuralized analysis was popularized by Demarcates in the year of 1979. In its book on the subject, I demarcate it introduced and it nominated graphical symbols that make possible the analyst to create models of flow of data and symbols. This symbol of graph and flowchart is of utmost importance for the analysts, therefore when the part of analysis of the system is becoming, it is of easiness to have an entity diagram relationship and diagram of data.

The analysis of the flow of data DFD is used as a graphical tool to describe the flow of information being one of the main tools used in the project of information systems. It is a diagram based on symbols, that show to the structure of the system and its border. In figure 1 we see a DFD example.