- High-level description of the data domain
- Does not constrain how that description is
mapped to an actual implementation in
software
Conceptual Data Model
Data Modelling Concept / Data Modelling
Conceptual Model
Logical Model
Physical Mode
- Being the scope of a model, it helps to
describe the semantics of a domain
Conceptual Model
There are description of Tables, Columns,
Object Oriented Classes, XML Tags,
Document Structure
Logical Model
This Model Cares about the actual physical
structure to store the data, like the
partitions, CPU Spaces, Replications,
Shards etc
Physical Model
Types of Data Models
Entity-Relationship (E-R) Model
UML (Unified Modeling Language)
- Only addresses data and relationships
- Classic, simplest
- Best for deriving a sound table design
- Many extensions/variations exist
- Basis for most other modeling approaches
Entity-Relationship (E-R) Models
- Class models
- Goes beyond data, also models behaviors
UML (Unified Modeling Language)
- Documentation of the structure of the
data - Used to communicate the design
- Serve as the basis for data model
implementation
Entity Relationship Model
- Technology independent
- Contains more detail than the Conceptual
Data Model - Considered by many to be just an
expanded conceptual data model
Logical Data Model
effectively become tables
Entities
describe entities and become
fields (columns) in tables
Attributes
link tables on a common
attribute or “key” and become formal
constraints (part of the business rules)
Relationships
- Multiple notation systems are used
- Each software program is a little different
- Most common is “Crows Foot”
ER Diagram Relationship Notation
maximum number of times
an instance in one entity can be associated
with instances in the related entity
- Can ONLY have values of 1 or many
- Located closest to the entity in Crow’s Foot notation
Cardinality
minimum number of times
an instance in one entity can be associated
with instances in the related entity
- Indicates whether an instance of an entity
MUST participate in the relationship
- Can ONLY have the values of 0 or 1
Participation
attribute that is a persistent, unique
identifier
Primary Key
in “parent” table
Primary key
in “child” table
Foreign key
Categories of Data Model
Relational Model
ER Model
Object-Based Model
Semistructured Data Model
- Tables represents both data and
relationships
Relational Model
- Collection of basic objects called entities
and its relationships
ER Model
- OOP Languages- C++, Java, C#, etc.
- Need for Object Oriented data model
Object-Based Model
- Specification of data
- Individual data items of the same type
may have different sets of attributes
Semistructured Data Model
