2. Definition of Data model:
* A set of concepts that can be used to describe the
structure of a database:
data types, relationships, constraints,
semantics and operational behaviour.
* It is a tool for data abstraction.
Data model operations :
Specifying database retrievals and updates by
referring to the concepts of the data model.
3. Categories of data models
Conceptual data model
Logical data model
Physical data model
4. 1-1. Data models (Conceptual data model)
• Identifying the business concepts (entities)
• Relationships between these concepts in order to gain,
reflect, and document understanding of the organization’s
business from a data perspective.
5. 1-1. Data models (Logical data model)
• Describes the data in as much detail as possible
6. 1-1. Data models (Physical data model)
• Specification all tables and columns.
• Foreign keys are used to identify relationships between tables.
7. Categories of database models
Flat database model
Hierarchical database model
Network database model
Relational database model
Object/Relational database model
Object-oriented database model
8. 1-2. Database models (Flat DB model)
• consists of a single, two-dimensional array of data elements.
• all members of a given column are assumed to be similar values.
• all members of a row are assumed to be related to one another.
9. 1-2. Database models (Hierarchical DB model)
• Organized into a tree-like structure
• A sort field to keep the records in a particular order in each
same-level list.
• widely used in the database management systems.
10. 1-2. Database models (Network DB model)
• Records and sets are using as fundamental constructs.
• Records contain fields, Sets define one-to-many relationships between records.
11. 1-2. Database models (Relational DB model)
• Allows the definition of data structures, storage and retrieval operations and
integrity constraints. And organised in tables.
• Records and each record in a table contains the same fields.
