The Enhanced Entity Relationship Model contains all the features of the Entity Relationship model. In addition to all that, it also contains features of Subclasses, Superclasses and Inheritance.All of these in detail are as follows −SubclassesA subclass is a class derived from the superclass. It inherits the properties of the superclass and also contains attributes of its own. An example is:Car, Truck and Motorcycle are all subclasses of the superclass Vehicle. They all inherit common attributes from vehicle such as speed, colour etc. while they have different attributes also i.e Number of wheels in Car is 4 while in Motorcycle ... Read More

Class hierarchy can be viewed one of two waysSpecialization (Top Down Approach)Generalization (Bottom Up Approach)SpecializationSpecialization is a process of identifying subsets of an entity that shares different characteristics. It breaks an entity into multiple entities from higher level (super class) to lower level (subclass). The class vehicle can be specialized into Car, Truck and Motorcycle ( Top Down Approach)Hence, vehicle is the superclass and Car, Truck, Motorcycle are subclasses. All three of these inherit attributes from vehicle. Moreover, these three share those attributes among themselves while containing some other attributes which make them different.GeneralizationGeneralization is a process of generalizing an entity which ... Read More

The detailed comparison on the E- R model and Object Oriented Model is given as follows −E-R ModelER model is used to represent real life scenarios as entities. The properties of these entities are their attributes in the ER diagram and their connections are shown in the form of relationships. An ER model is generally considered as a top down approach in data designing.An example of ER model is −Advantages of E - R modelThe data requirements are easily understandable using an E - R model as it utilises clear diagrams.The E-R model can be easily converted into a relational database.The ... Read More

In object based data models, the focus is on how data is represented. The data is divided into multiple entities each of which have some defining characteristics. Moreover, these data entities are connected with each other through some relationships.So, in object based data models the entities are based on real world models, and how the data is in real life. There is not as much concern over what the data is as compared to how it is visualised and connected.Some examples of object based data models areEntity Relationship Data ModelObject Oriented Data ModelSemantic Data ModelFunctional Data ModelOut of these models, ... Read More

ER model is used to represent real life scenarios as entities. The properties of these entities are their attributes in the ER diagram and their connections are shown in the form of relationships.Some examples of ER model are −Hospital ER ModelThis is an ER model of a Hospital. The entities are represented in rectangular boxes and are Patient, Tests and Doctor.Each of these entities have their respective attributes which are −Patients - ID(primary key), name, age, visit_dateTests- Name(primary key), date, resultDoctor- ID(primary key), name, specializationThe relationships between different entities are represented by a diamond shaped box.Company ER ModelThe entities in this ... Read More

An entity is similar to a unique object and a collection of attributes. There are two types entities namely strong entity and weak entity. A strong entity is an independent entity. On the other hand, a weak entity is a dependent entity that depends on a strong entity. Read through this article to find out more about strong and weak entities and how they are different from each other. What is a Strong Entity? A strong entity is complete by itself and is not dependent on any other entity type. It possess a primary key which describes each instance in ... Read More

Mandatory and optional participation are observed in E-R models between 2 different entities.Mandatory ParticipationIn the mandatory participation, for every instance of entity A, there must exist an instance of entity B and vice versa.An example of Mandatory participation would be relationship between mother and child. The child entity would exist only if there were a mother and similarly a mother would exist only if there were a childOptional participationIn optional participation, it is not necessary for all the instances of the entity to participate in a relationship. It may be that the number of instances participating for a particular entity ... Read More

Moving objects are those whose position changes frequently over a period of time. Conventional databases don't know how to handle this scenario, as they assume the data objects are stationaryIn this case, we use moving object databases. These databases can store information about moving objects and allow querying on them.For example- The location of nearest taxis for a particular customer can be found using querying on moving object databases.The approaches used in handling moving object databases are:Location ManagementThe current locations of the objects are saved in the database and estimations are made on their near future positions. This information is ... Read More

GeneralizationGeneralization is a process of generalizing an entity which contains generalized attributes or properties of generalized entities. The entity that is created will contain the common features. Generalization is a Bottom up process.We can have three sub entities as Car, Truck, Motorcycle and these three  entities can be generalized into one general super class as Vehicle.It is a form of abstraction that specifies two or more entities (sub class) having common characters that can be generalized into one single entity (super class) at higher level hiding all the differences.SpecializationSpecialization is a process of identifying subsets of an entity that shares ... Read More

EER is a high-level data model that incorporates the extensions to the original ER model. Enhanced ERD are high level models that represent the requirements and complexities of complex database.In addition to ER model concepts EE-R includes −Subclasses and Super classes.Specialization and Generalization.Category or union type.Aggregation.These concepts are used to create EE-R diagrams.Subclasses and Super classSuper class is an entity that can be divided into further subtype.For example − consider Shape super class.Super class shape has sub groups: Triangle, Square and Circle.Sub classes are the group of entities with some unique attributes. Sub class inherits the properties and attributes from ... Read More