These days, I am studying the books about how to design and create a database for our term project and lecture. I have sawn some knowledge about the E-R model naturally. And in this time we were suggested to read the paper of Pin-Shan Chen about E-R model. So I have more understand of it.

      The first step to design a database is structure design. And the first things to do for structure design is concept structure design which accomplish the transformation of real world to the world of information (Computer) and the building of the data models.

The major data models are the network model, the relational model and the entity set model before. And in this paper of Pin-Shan Chen, the entity-relationship model, which has most of the advantages of the above three models. For example, the entity-relationship model can achieve a high degree of data independence and is based on set theory and relation theory. So in general, the concept model is expressed by E-R diagram.

So far as I know, to simplify the model, it is more effective to make the real affairs be the attributes of the E-R model than an entity (Attributes have no descriptive characteristics and is not relational with any entities). Let us see the E-R diagram when the dormitory is an attribute and the E-R diagram when the dormitory is an entity.

When we talk about the student, Birthday, ID number, Name, Sex and Major are attributes. If we need concern about the Dormitory and need to write down the dormitory number, the dormitory number is an attribute of student. But when we need more details of dormitory like Management expense, Administrator, Dormitory number and Time of be completed, the Dormitory will be an entity.

○--entity ;  □-- attribute ;  ◇-- relationship

Fig 1: The E-R diagram when the dormitory is an attribute

Fig 2: The E-R diagram when the dormitory is an entity

When the E-R model (concept structure design) is completed, we need transform the E-R model to relational model. The important things in this step are how to transform the relation between entity and entity to relational pattern of relational model and how to determine the attribute and key if relational pattern.

The transform the E-R model to relational model have two steps: transformation of entities and transformation of relationship between entities.

It is not difficult to read the Pin-Shan Chen`s paper when it based on the E. F. Codd`s paper. It encouraged me to learn about Database theory even if knowledge of it is difficult or the papers are written by English.