In my previous article I wrote about the distant flow chart and currently not used much, except to the teaching of the origins of the database. Now first let's look at the role of data analysis. Takes place throughout the development cycle, but at different levels of detail. Typically, the analysis begins by developing the top-level conceptual model of the current system. You will find that many analysts start with the analysis of data before starting to develop a model of data flow. Others begin the data analysis when the DFD is over, and others to develop at the same time.
Some detailed data analysis take place during the analysis of systems so that the analyst and the designer are aware of data that are currently available in the system. However, the level design, which requires relational analysis, does not occur until the design phase detallado.Tengo clarified that the Entity-Relationship Model is a conceptual model for later database design. But we split. Entity-Relationship Model consists of several symbols together according to certain conventions that describe how to get the conceptual model using the method known as entity-relationship analysis. Koch addresses the importance of the matter here. This method was first introduced by Chen in 1976, and now I have to say (2010) is widely used by designers, after all, surely nobody will remember this man. The entity-relationship analysis uses three major abstractions to describe data. Koch Brothers: the source for more info. These are: Entities, things distinguishable in the company; Relationships and interactions between objects, and Attributes, properties of entities and relationships.
In the entity-relationship diagrams (ER) has a more concise representation. ER diagrams represent no entity or individual relationships, only represent entity sets and relationship. For this purpose, rectangular boxes and diamonds. It is particularly important to use consistent terminology to understand data analysis. Data analysis avoids the computer as much as possible, to prevent any preconceptions about computer structures that emerge from the analysis. Obviously, the sets become types of records later, during the design of a computer system. The distinction between occurrences and sets of relationships entail. Occurrences are also of relations and sets of relationships are more difficult to perceive than entity sets. You can see entities, but not see relationships. This makes analysis difficult, it is necessary to create models that do not exist physically as simple objects. However, if you force the imagination one can discern a relationship occurrence as a person working on a project, this would be an example of an occurrence. In the next installment will come fully into the Classes and Objects, sure to be interesting reading.