Enhanced Entity Relationship Model (EER Model)
The primary features added by the Enhanced ER Model are specialization/ generalization and unions. Of these Gen-spec is the one that most often comes up in. Source from: Enhanced entity–relationship model; Difference between ER diagram and EER diagram; Enhanced Entity Relationship Diagram (ERD). What is the difference between ERD (Entity relationship diagram) and The result is EER, stands for Extended ER modeling or Enhanced ER.
- Entity–relationship model
- Enhanced Entity Relationship Model (EER Model)
- Entity-Relationship model
Sub Class Sub class is a group of entities with unique attributes. Sub class inherits properties and attributes from its super class.
Square, Circle, Triangle are the sub class of Shape super class. Specialization and Generalization 1. Generalization Generalization is the process of generalizing the entities which contain the properties of all the generalized entities.
database - Difference between ER diagram and EER diagram - Stack Overflow
It is a bottom approach, in which two lower level entities combine to form a higher level entity. Generalization is the reverse process of Specialization. It defines a general entity type from a set of specialized entity type. It minimizes the difference between the entities by identifying the common features. In the above example, Tiger, Lion, Elephant can all be generalized as Animals.
Specialization Specialization is a process that defines a group entities which is divided into sub groups based on their characteristic. It is a top down approach, in which one higher entity can be broken down into two lower level entity. It maximizes the difference between the members of an entity by identifying the unique characteristic or attributes of each member.
For example In the above example, Employee can be specialized as Developer or Tester, based on what role they play in an Organization. Category or Union Category represents a single super class or sub class relationship with more than one super class.
It can be a total or partial participation. When trying to calculate sums over aggregates using standard SQL over the master table, unexpected and incorrect results.
The solution is to either adjust the model or the SQL. This issue occurs mostly in databases for decision support systems, and software that queries such systems sometimes includes specific methods for handling this issue. The second issue is a 'chasm trap'. A chasm trap occurs when a model suggests the existence of a relationship between entity types, but the pathway does not exist between certain entity occurrences. For example, a Building has one-or-more Rooms, that hold zero-or-more Computers.
One would expect to be able to query the model to see all the Computers in the Building.
However, Computers not currently assigned to a Room because they are under repair or somewhere else are not shown on the list. Another relation between Building and Computers is needed to capture all the computers in the building.
This last modelling issue is the result of a failure to capture all the relationships that exist in the real world in the model. See Entity-Relationship Modelling 2 for details.
What is the difference between ER and EER model in database?
Entity—relationships and semantic modeling[ edit ] Semantic model[ edit ] A semantic model is a model of concepts, it is sometimes called a "platform independent model". It is an intensional model. At the latest since Carnapit is well known that: The first part comprises the embedding of a concept in the world of concepts as a whole, i. The second part establishes the referential meaning of the concept, i. Extension model[ edit ] An extensional model is one that maps to the elements of a particular methodology or technology, and is thus a "platform specific model".
The UML specification explicitly states that associations in class models are extensional and this is in fact self-evident by considering the extensive array of additional "adornments" provided by the specification over and above those provided by any of the prior candidate "semantic modelling languages".Enhanced ER Diagram(EER) in hindi -- MCS-043
It incorporates some of the important semantic information about the real world. Plato himself associates knowledge with the apprehension of unchanging Forms The forms, according to Socrates, are roughly speaking archetypes or abstract representations of the many types of things, and properties and their relationships to one another.
Limitations[ edit ] ER assume information content that can readily be represented in a relational database. They describe only a relational structure for this information. They are inadequate for systems in which the information cannot readily be represented in relational form[ citation needed ], such as with semi-structured data.