What are extended ER features in DBMS?

What are extended ER features in DBMS?

The extended E-R features are specialization, generalization, higher- and lower-level entity sets, attribute inheritance, and aggregation. An entity set may include subgroupings of entities that are distinct in some way from other entities in the set.

What are different EER notations?

There are two kinds of ER diagrams: conceptual and physical. Conceptual diagram models can be used as the foundation for logical data models or to form commonality relationships between ER models as a basis for data-model integration.

What is symbol of entity in ER diagram?

An entity is an object or component of data. An entity is represented as rectangle in an ER diagram.

What are the features of ER diagram in DBMS?

Also known as ERDs or ER Models, they use a defined set of symbols such as rectangles, diamonds, ovals and connecting lines to depict the interconnectedness of entities, relationships and their attributes. They mirror grammatical structure, with entities as nouns and relationships as verbs.

What is the meaning of extended ER models?

Definition. The extended entity-relationship (EER) model is a language for defining the structure (and functionality) of database or information systems. Its structure is developed inductively. Basic attributes are assigned to base data types.

How do you draw an EER diagram?

How to Draw an Entity Relationship Diagram

1. Determine the Entities in Your ERD. Start by identifying the “what”s in your system or architecture.
2. Add Attributes to Each Entity.
3. Define the Relationships Between Entities.
4. Add Cardinality to Every Relationship.
5. Finish and Save Your ERD.

What is superclass and subclass in ER model?

A superclass is the class from which many subclasses can be created. The subclasses inherit the characteristics of a superclass. The superclass is also known as the parent class or base class. In the above example, Vehicle is the Superclass and its subclasses are Car, Truck and Motorcycle.

What do double diamonds represent in an ER diagram?

Explanation: Diamonds represent relationship sets in an ER diagram. Relationship sets define how two entity sets are related in a database. Explanation: The double diamonds represent the relationship sets linked to weak entity sets.

How are the elements in ER model are represented draw and name the elements?

There are three basic elements in an ER Diagram: entity, attribute, relationship. They are weak entity, multi valued attribute, derived attribute, weak relationship, and recursive relationship. Cardinality and ordinality are two other notations used in ER diagrams to further define relationships.

How inheritance is represented in ER diagram?

2 Answers. inheritance relationship in ERD should be represented as One-To-One relationship or One or Zero-to-One relationship depending on the case.

How do you draw an enhanced entity relationship diagram?

How to Draw ER Diagrams

1. Identify all the entities in the system. An entity should appear only once in a particular diagram.
2. Identify relationships between entities. Connect them using a line and add a diamond in the middle describing the relationship.
3. Add attributes for entities.