Database Architecture Fundamentals: Models and Components

Client Module Functions

The Client Module usually runs on a workstation or personal computer. Normally, application programs and user interfaces that access the database run on the client module.

Server Module Responsibilities

The Server Module typically manages storage, access, data mining, and other essential database functions.

Understanding the Data Model

A fundamental characteristic of the database approach is that it provides some level of data abstraction by hiding storage details that most users do not need to know. A Data Model is:

• A collection of concepts used to describe the structure of a database.
• The means to achieve data abstraction.

Database Structure Components

The structure of a database refers to the data types, relationships, and constraints that must be met for the data. Most data models also contain a set of basic operations to specify reads and updates to the database.

Conceptual (High-Level) Data Models

Conceptual models (like the Entity-Relationship (ER) and Object-Oriented (OO) models) have concepts very close to the way most users perceive the data.

Physical (Low-Level) Data Models

Physical models provide concepts that describe the details of how data is stored on the computer.

Representation and Implementation Models

Models of representation and implementation (such as the relational data model, network model, and hierarchical model) have concepts that can be understood by end users but are not too far removed from how data is organized within the computer. They hide some details of data storage.

Key Concepts in Conceptual Models

Conceptual models use concepts such as entities, attributes, and relationships:

• Entity: Represents an object or concept in the real world, such as an employee or a project.
• Attribute: Represents a property of interest that gives a more detailed description of an entity (e.g., name or employee's salary).
• Relationship: Describes an interaction between two or more entities (e.g., the relationship "works on" between an employee and a project).

Physical Model Details

Physical models describe how data is stored on the computer using information representation, such as record formats, search structures, and access paths.

An access path is a structure that performs the search for specific records in the database efficiently.