Data models can be record-based (hierarchical, network, relational), object-based (entity-relationship, semantic, functional, object-oriented), or physical (unifying frame memory). The entity-relationship model is a method to visualize data logically and independently of hardware. It facilitates database design by allowing specification of entity types, relationships between entities, and attributes of entities. The main concepts are entities, relationships between entities, and attributes of entities.
Entity type
Entity sets
Attributes and keys
Relationship model
Mapping Constraints
The ER Model
Cardinality Constraints
Generalization, Specialization and Aggregation
ER Diagram & Database design with the ER Model
Introduction
Relational Model
Concepts
Characteristics
Entity type
Entity sets
Attributes and keys
Relationship model
Mapping Constraints
The ER Model
Cardinality Constraints
Generalization, Specialization and Aggregation
ER Diagram & Database design with the ER Model
Introduction
Relational Model
Concepts
Characteristics
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Initially launched in Chicago, our social media network will be available shortly afterwards in all United States on desktops, smartphones and tablets. We have an initial cost of $175,000; the app should bring us more than $650,000 profit for the third years and we expect 2ndYouth to exceed 1 million subscribers by then. The main danger for our development is probably Meetup.com, actual leader for local community meets. Indeed, features are pretty much the same, however seniors are also in need of a simple and personalized service for their community, that Meetup.com doesn’t offer.
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chapter 3-Data Modelling using Entity Relationship .pdfMisganawAbeje1
it describes about Data Model Basic Building Blocks in Using High level Data Models for Database Design Entity types and Sets, Attributes and Keys, Relationships, Roles and Structural Constraints, Enhanced ER Diagram, E-R mapping to Relational Database model.
It's a slide on business related topics. For example it would increase your knowledge on business facts. Business is a must onowning factor in todays world. The whole world runs on business. Without business its not possible to maintain balance. In the world we should do business for living well. Throughout the earth its very important for the mankind.
Data modeling is a process used to define and analyze data requirements needed to support the business processes within the scope of corresponding information systems in organizations.
2. DATA MODELS
Data models can be
Record-based
Object-based
Physical
Record-based data models
Hierarchical model
Network model
Relational model
Object-based data models
Entity-relationship
Semantic
Functional
Object-oriented
Physical data models
Unifying model
Frame memory model
3. E-R Model
A method of communication amongst different
designers, programmers and end-users who tend to view
the data.
A non-technical, standard and logical way of visualizing
data.
An informal description of what users want from their
database.
A detailed and precise description which can be
implemented in a DBMS.
It is independent of any particular database management
system and hardware platform.
Facilitate database design by allowing specification of an
enterprise schema.
4. E-R Model concepts
The three main semantic concepts are :
Entities
Relationships
Attributes
Constraints ( on all of the above concepts)
Entities
An entity is an ‘object’ ( building , toy), an event (
sale, competition), a place ,a person or a concept (Course
, Account).
Entity type or set and entity instance :
Is a set of entities of the same type that share the same
properties.
Each entity type is identified by a name and a list of
attributes.
A database contains many different entity types .
5. E-R Model concepts
An entity corresponds to a table not to a row.
A table row is an entity instance.
An entity occurrence is an uniquely identifiable object of an
entity type.
Relationship
Is an association among two or more entities.
Similar relationships are grouped into relationship sets.
The relationship name describes its function.
Relationships are described in
Degree
Connectivity
Existence
n-ary relationship
6. E-R Model concepts
Attribute
Domain
Sub domain
Attribute domain
Attribute can be
Simple attribute
Composite attribute
Single-valued attribute(PID)
Multi-valued attribute (skill)
Derived attribute
Identifier attribute
