DBMS L2

Lesson 2: INTRODUCTION TO MODELLING

Business Rules

Statements that define or constrain some aspect of the business.

Good Business Rule is

Declarative; Precise; Atomic; Consistent; Expressible; Distinct; Business-oriented

Term

Word or phrase with specific meaning.

Fact

Association between two or more terms.

Conceptual data modelling

A detailed model that shows the overall structure of organizational data while being independent of any database management system or other implementation considerations.

Top Five Reasons to Model

• Easy to Change.

• Communication Method to Gather Requirements.

• Business Rules Validation.

• Target User Involvement.

• Documentation.

Data Models in DBMS

Is the concept of tools that are developed to summarize the description of the database.

Conceptual Data Model

Describes the database at a very high level and is useful to understand the needs or requirements of the database.

Entity-Relationship Model (ER Model)

A high-level data model that is used to define the data and the relationships between them.

Representational Data Model

Used to represent only the logical part of the database and does not represent the physical structure of the database.

Relational Algebra

A procedural query language, it tells the database how to retrieve data.

Relational Calculus

A non-procedural (declarative) query language, it specifies what data to retrieve, not how to retrieve it.

Physical Data Model

Used to practically implement the Relational Data Model. In the form of files, records, and certain other data structures.

Multidimensional Model

A model of business activities in terms of facts and dimensions.

Approaches to Modeling

• Top-down modeling.

• Bottom-up modeling.

• Targeted modeling.

Top-Down Modeling

Designing a New Database

Bottom-Up Modeling

Modifying an Existing Database

Targeted Modeling

Maintaining Existing Models by Adapting to New Requirements