Creating an Entity Relationship Diagram

An entity relationship diagram enables a software engineer to fully specify the   data   objects which are input  and  output from  a  system the  attributes and  describe  the  properties of  these  objects and  the relationships among objects.  Such as most parts of the analysis model the ERD is constructed in an iterative manner. The following approach is taken for this construction which is given below;

1.  In the duration of requirements gathering the customers are asked to list the things in which the application or business process addresses. Things evolve into a list of input and output data objects as well as external entities which produce or consume information.

2.  Taking the objects one at a time the customer and analyst describe whether or not a connection exists among the data object and other objects.

3.  Anywhere a connection exists the analyst and customer build one or more object relationship pairs.

4.  For each object relationship pair modality and cardinality are explored.

5.  Step 2 by 4 is continued iteratively until all object relationship pairs have been described. It is general to discover omissions as this procedure continues. New relationships and objects will invariably be added as the number of iterations grows.

6.  The attributes of each entity are described.

7.  An entity relationship shows is reviewed and formalized.

8.  Steps one by seven are repeated until data modeling is complete.