Data Modeling

In class, I knew the concept of modeling and the great benefits it brings in some fields. Data model is characteristic abstract data. It helps to build clear relationship. Conceptual data model is one form of the modeling, especially E-R data model, which is one of the common conceptual data modeling. It is interesting for me to consider their internal relationships.

The basic shape is to describe the entities in rectangular frames. The attributes are described by ellipse. The relationships of different entities are showed by rhombic frame and appropriate named by underlying meaning. Use the lines to connect the rectangular frames and rhombic frame. If a person wants to know the multiple relationships between the two different entities, he should first confirm the attributes between two entities, and then define the types of relationships, finally combine attributes with the entities and the relationships .For example, a department consists of many students and a student can choose different courses, and the same courses can be chosen by different students. Therefore, the two above relationships are one-to –many and many-to –many. To express the three objects or more, the key is to build two relationships among the three objects.

The divide between entities and relationships is that when the behavior is happened among these entities, it is necessary to build relationship set or connect all the attributes of entities.