Data Modelling

Data Modelling

When it comes to Model Driven Software Development, the first thing that we learners need to know is Data Modelling, because it is the basic elements elements. In this essay, I am going to talk about my comprehension about Data Modelling, also the application of this kind of modelling will be referred as well.

To begin with, Data Modelling is used for modelling unchangeable things which exists in the real world, no matter it is a real thing or a virtual one. In other word, as long as the thing is static, it can be modelled by data modelling.

Basically, Data Modelling could be divided into three major elements, class, attribute and relationship. According the our lecture note, a class is a general entities, which has a number of common entities. It is similar to a java class, which could be used in more than one object. For attribute, it is related to each entity, which is used to describe each class. For example, for a student class, it should has name, DOB, sex, major, minor (etc) as main attributes. In this case, all students could be described in the student class, although the value for each attribute might be different. For association, it is used to describe the relationship between each two entities. For instance, student enrolls in course, which means there is an enroll association between student class and course class. Personally, it is the most important factor in Data Modelling, because it is the these relationships which makes software project much harder.

The diagram above illustrates the main process of data modelling (West and Fowler, 1999). According to the diagram, we create logical data model initially, which is based on activity model and data requirements. Then we focus on creating or updating the model in physical part, in this situation, technical environment and performance consideration will be taken into account, also conceptual data model will be used in this part, such as entities, attributes, relationships and integrity rules. Next, we create data, which is from physical data model and real business data. Finally, the data we created or updated is what we want from data modelling.

There are a number of famous data modelling application in our real work. One of them is database. Basically, the database of one system stores all static information, which indicates the class attributes and associations. Take the following ER diagram as an example:

From the diagram, we can create the database with the database rules, which means that these creation steps could be viewed as process management, and that is why database is called database system management (DBSM).

If we use the process management, once the diagram is well-development, the change having error is much smaller than using normal method， also it could save time, because all database schemas could be created by the rules.

In conclusion, data modelling is useful in developing a project.

Reference:

Matthew West and Julian Fowler (1999). Developing High Quality Data Models. The European Process Industries STEP Technical Liaison Executive (EPISTLE).