Data modelling of e-business and e-commerce systems uses well-established techniques such as normalization that are used for relational database analysis and design. As a consequence, this section is brief in comparison with that on process modelling which introduces some novel techniques. See Bocij et al. (2005, Chapter 11) for an introduction to normalization and relational database design. Some basic definitions are given in this section as a reminder of key terms. Before we start it is worth mentioning that the advent of data mining and object-oriented approaches has meant increasing use of non-relational database design. These are outlined further in Chapters 6 and 11 of Bocij etal. (2005).
The approach we use to explore data modelling for e-commerce is to use examples that identify typical elements of data modelling for a sell-side e-commerce system. We will use ER (entity relationship) modelling to review typical structures for these databases. In simple ER modelling there are three main stages.
1. Identify entities
Entities define the broad groupings of information such as information about different people, transactions or products. Examples include customer, employee, sales orders, purchase orders. When the design is implemented each design will form a database table.
2. Identify attributes for entities
Entities have different properties known as ‘attributes’ that describe the characteristics of any single instance of an entity. For example, the customer entity has attributes such as name, phone number and e-mail address. When the design is implemented each attribute will form a field, and the collection of fields for one instance of the entity such as a particular customer will form a record.
3. Identify relationships between entities
The relationships between entities require identification of which fields are used to link the tables. For example, for each order a customer places we need to know which customer has placed the order and which product they have ordered. As is evident from Figure 11.5, the fields customer id and product id are used to relate the order information between the three tables. The fields that are used to relate tables are referred to as ‘key fields’. A primary key is used to uniquely identify each instance of an entity and a secondary key is used to link to a primary key in another table. In Figure 11.5 the primary key of the customer table is customer id, but the field customer id in the order table is here a secondary key that links back to the customer table. This relationship is an example of a one-to-many relationship since each customer may place many orders over the lifetime of the relationship.
Normalization is an additional stage, not covered here, used to optimize the database to minimize redundancy or duplication of information.
If you have previous experience in analysis and design for databases, complete Activity 11.3 to develop an ER diagram for a typical B2C company. If you do not have this experience then refer to the generic answers to gain an appreciation of how databases are structured.
Source: Dave Chaffey (2010), E-Business and E-Commerce Management: Strategy, Implementation and Practice, Prentice Hall (4th Edition).
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