1.1 Theoretical Background
1.1.1 Relational Model Design
There are two methods to design a relational data model. The type of method applied by data modeler is dependant on the size and complexity of database. These two methods
include:
1. Traditional Approach
This approach is applied to develop smaller or simpler database
Based on set of system requirements, two-dimensional table structures are
created randomly
The tables need to undergo normalization process before a complete relational data model can be produced
Figure 1-1 illustrates traditional approach for relational data model design.
Figure 1-1 : Traditional approach. 2.
Semantic Modeling Approach
This approach is adopted in developing large and complex database
Semantic model is transformed to Relational model
Real -world information
Random Tables
Normalized Relational
Data Model
2
Figure 1-2 illustrates semantic modeling approach for relational data model design.
Figure 1-2: Semantic modeling approach.
This practical applies the second method of relational data modeling, which is called semantic modeling. Semantic model is referred as a generic model since it is
independent with type of DBMS used. In this approach, database designer adopts one of two approaches namely Object-based data model or entity-relationship ER model. ER
is the most common approach to design relational data model and for this purpose, ERD Entity Relationship Diagram is used.
Once conceptual data model is completed, it needs to be transformed into a logical data model. Data model transformation is shown in Figure 1-3.
Figure 1-3 Data model transformation flow.
Real -world information
Semantic Conceptual
Data Model Relational
Data Model
Real -world information
Semantic Conceptual
Data Model Relational
Data Model
Requirements Definition
LOGICAL DESIGN
PHYSICAL DESIGN
Object-based Data Model
OR
Entity-Relationship Model
3
1.1.2 Mapping conceptual design to logical design using relational data model
The result of transformation from conceptual design to logical design can be summarized in the following table :
Table 1-1: Mapping conceptual design to logical design Semantic Data Models Conceptual Design
Relational Data Model Logical Design
Entity-relationship data model
Object-based data model
Entity types Object set
Relations or tables Attributes
Attributes Columns
Key attributes Identifiers
Primary Key Relationships
Relationships Foreign Key
4
The following exercise requires the students to apply and demonstrate their understandings in designing a relational database application. Based on the system
requirements provided, students should be able to develop conceptual data model using ERD and logical data model using Relational notation. At the end of the process, they
need to implement the data model using a relational DBMS.
1.2 Exercise
1.2.1 ConceptualSemantic Data Model for Banking Enterprise
Consider that a bank keeps track of customers, employees, accounts and bank’s loan. Develop a Chen ERD Entity relationship diagram based on these requirements:
Note: Refine the ERD if necessary.
The bank is organized into branches. Each branch is located in a particular
city and is identified by a unique name. The bank monitors the assets of each branch. A branch can originate one or more loans.
Bank customers are identified by their customer-id values. The bank stores
customer’s name, street and city where the customer lives. Customer may have accounts and can take out loans. A customer may be advised by a particular
bankeremployee, who may act as loan officer or personal banker for that customer, and that particular banker can advise one or more customers.
Bank employees are identified by their employee-id values. The bank
administration stores the name and telephone number of the employee, the names of employee’s dependents and the employee-id of the employee’s
manager. The bank also keeps track of the employee’s start date and the length of employment. An employee works for only one manager and that manager
supervises one or more employees.
5
Kategori