Data Models in Database Systems: Types, Evolution, and Abstraction Levels

Data modeling

The process of creating a conceptual representation of data structures to reduce complexity and reconcile different stakeholder views.

Data model

A simple, often graphical, representation of real-world data structures.

Model

An abstraction of a real-world object or event.

Entity

A thing about which data is collected.

Attribute

A property of an entity.

Relationship

An association between entities.

Constraint

A restriction on data.

Business Rules

Policies, procedures, and principles that define data characteristics and required actions in an organization.

Sources of Business Rules

Managers, policy makers, documentation, manuals, interviews.

Purpose of Business Rules

To standardize a company's data view, improve communication between users and designers, and define scope and relationships.

Nouns → Entities

A method for translating business rules into data models.

Verbs → Relationships

A method for translating business rules into data models.

Hierarchical Model

A data model from the 1960s characterized by a tree structure and parent-child relationships.

Network Model

A data model that allows records to have multiple parents and is effective for complex relationships.

Schema

The entire database view in the network model.

Subschema

An application-specific view in the network model.

DML/DDL

Data Manipulation Language/Data Definition Language used for managing and defining data.

Relational Model

A data model introduced in 1970 by E.F. Codd, consisting of tables (relations) made up of rows (tuples) and columns (attributes).

Entity-Relationship (ER) Model

A graphical representation of entities and relationships, including concepts like entity sets and connectivity.

Object-Oriented (OO) Model

A data model that combines data and relationships into a single object.

ERDM (Extended Relational Data Model)

A model that combines relational and object-oriented features.

XML

A standard for Internet-based data exchange, supported by modern database management systems.

Hybrid DBMS

A database management system that combines relational and object-oriented views.

SQL Data Services

Cloud-based, pay-as-you-go databases.

External Model

The end-user view represented by ER diagrams and external schemas.

Conceptual Model

A global organizational view represented by an ERD, independent of software and hardware.

Internal Model

The representation of data as seen by the DBMS, providing logical independence.

Physical Model

The lowest level of abstraction that defines how data is stored and accessed.