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An entity–relationship model (or ER model) describes interrelated things of interest in a specific domain of knowledge. A basic ER model is composed of entity types (which classify the things of interest) and specifies relationships that can exist between entities (instances of those entity types).
For example, as soon as you want to find seasonal or geographical trends in the sales of the item, you need information from the related Order record. An order would not exist without a product and a person to create the order, so it could be argued that an order would be described as a weak entity and that products ordered would be a ...
An associative entity is a term used in relational and entity–relationship theory. A relational database requires the implementation of a base relation (or base table) to resolve many-to-many relationships. A base relation representing this kind of entity is called, informally, an associative table. An associative entity (using Chen notation)
Attributes in ER diagrams are usually modeled as an oval with the name of the attribute, linked to the entity or relationship that contains the attribute. ER models are commonly used in information system design; for example, they are used to describe information requirements and / or the types of information to be stored in the database during ...
For example, data may be modeled by ER diagrams, and behaviors by flow charts or structure charts. Common models used in OOA are use cases and object models. Use cases describe scenarios for standard domain functions that the system must accomplish. Object models describe the names, class relations (e.g. Circle is a subclass of Shape ...
The enhanced entity–relationship (EER) model (or extended entity–relationship model) in computer science is a high-level or conceptual data model incorporating extensions to the original entity–relationship (ER) model, used in the design of databases.
The SERM (structured entity relationship model) is an amplification of the ERM which is commonly used for data modeling. It was first proposed from Prof. Dr. Elmar J. Sinz in 1988. The SERM is commonly used in the SAP -world for the data modeling .
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