Data Models In ADBMS

In Advanced Database Management Systems (ADBMS), several types of data models are used to represent and organize data in complex and efficient ways. These data models help in designing and implementing databases that cater to the specific needs of different applications and industries. Here are some common types of data models used in ADBMS:

 

1.     Relational Data Model: The relational model is one of the most widely used data models. It represents data as tables (relations) with rows and columns, and it defines relationships between tables using keys. SQL (Structured Query Language) is commonly used to work with relational databases.

 

2.     Entity-Relationship Model (ER Model): The ER model is used to describe the structure of data in terms of entities, attributes, and the relationships between entities. It's a popular choice for conceptual database design.

 

3.     Object-Oriented Data Model: In this model, data is represented as objects, similar to object-oriented programming. It supports features like encapsulation, inheritance, and polymorphism, making it suitable for complex data structures.

 

4.     Object-Relational Data Model (ORDBMS): ORDBMS combines features of the relational and object-oriented data models. It extends the relational model to support complex data types and methods/functions associated with those types.

 

5.     Hierarchical Data Model: This model represents data as a tree-like structure, with parent-child relationships. It is commonly used in scenarios where data naturally follows a hierarchical pattern, such as representing file systems.

 

6.     Network Data Model: Similar to the hierarchical model, the network data model represents data as a collection of records connected by links. It allows for more flexible relationships between records than the hierarchical model.­­

ER Model:

 

The Entity-Relationship (ER) model is a data modeling technique used to describe the structure of a database in terms of entities, attributes, and the relationships between entities. It's a widely used method for conceptual database design and helps in visualizing how data is organized and related within a system. Below, I'll explain the key concepts of the ER model and provide an example Entity-Relationship diagram.

 

Key Concepts in the ER Model:

 

Entity: An entity is a real-world object or concept with attributes that describe its properties. Entities are typically nouns, such as "Customer," "Product," or "Employee." Each entity is uniquely identifiable and can be represented as a rectangle in an ER diagram. 

 

Strong Entity: A strong entity is an entity that has a primary key attribute, and its existence does not depend on any other entity. Strong entities can exist independently and have attributes that define their properties.

 

Weak Entity: A weak entity is an entity that does not have a primary key attribute or has a partial key that is not sufficient to uniquely identify instances of the entity. Weak entities depend on a related strong entity (known as the owner entity) for their identity.

 

Attribute: An attribute is a property or characteristic of an entity. Attributes provide additional information about the entity. For example, a "Customer" entity may have attributes like "CustomerID," "Name," and "Email." Attributes are typically represented as ovals in an ER diagram and are connected to their respective entities.

Types of Attributes:

In the context of database design and the Entity-Relationship (ER) model, attributes are properties or characteristics that describe entities. Attributes provide more information about an entity and help define its properties. There are several types of attributes, each with its characteristics and use cases. Here are some common types of attributes:

 

Simple Attribute: A simple attribute is an attribute that cannot be divided further into smaller, meaningful parts.

 For example, the "Age" attribute of a person is a simple attribute because it is not broken down into subcomponents.

 

Composite Attribute: A composite attribute is an attribute that can be divided into smaller, meaningful subattributes with independent meanings.

For example, the "Address" attribute of a person can be divided into subattributes like "Street," "City," "State," and "Postal Code."

 

Derived Attribute: A derived attribute is an attribute whose value can be derived from other attributes in the database.

For example, the "Age" attribute of a person can be derived from the "Date of Birth" attribute.

 

Multi-valued Attribute: A multi-valued attribute is an attribute that can hold multiple values for a single entity.

For example, the "Phone Numbers" attribute of a person can have multiple phone numbers associated with it.

 

Key Attribute: A key attribute is an attribute that is used as a unique identifier for an entity. It helps distinguish one entity from another within the same entity set. Primary keys are examples of key attributes.

 

Single-valued Attribute: A single-valued attribute is an attribute that holds a single value for each entity. Most attributes are single-valued by default.

For Example, Date of birth attribute have only single value. 12/05/2012

 

Null Attribute: A null attribute is an attribute that may not have a value for some entities. Null attributes are used to represent missing or unknown data.

 

 

Relationship: A relationship represents an association between two or more entities. It shows how entities are related to each other. Relationships are typically represented as diamond shapes in an ER diagram. They can have names that describe the nature of the association, such as "owns," "works for," or "purchases."

 

Cardinality: Cardinality defines the number of instances of one entity that can be associated with the number of instances of another entity through a relationship. Common cardinality notations include "1" (one), "0..1" (zero or one), "0..n" (zero to many), and "1..n" (one to many).

One-One Relationship:

One-To-Many Relationship:

One-To-Many Relationship:

 

Symbols Used in ER Diagrams

Rectangles: This Entity Relationship Diagram symbol represents entity types

Ellipses: This symbol represents attributes

Diamonds: This symbol represents relationship types

Lines: It links attributes to entity types and entity types with other relationship types

Primary key: Here, it underlines the attributes

Double Ellipses: Represents multi-valued attributes

 

 

 

Example of ERD

1.     Student Attendance Management System

 

2.