ER-Diagram
Databases are used to store structured data. The structure of this data, together with other constraints, can be designed using a variety of techniques, one of which is called entity-relationship modeling or ERM. The end-product of the ERM process is an entity-relationship diagram or ERD. Data modeling requires a graphical notation for representing such data models. An ERD is a type of conceptual data model or semantic data model.The first stage of information system design uses these models to describe information needs or the type of information that is to be stored in a database during the requirements analysis. The data modeling technique can be used to describe any ontology (i.e. an overview and classifications of used terms and their relationships) for a certain universe of discourse (i.e. area of interest). In the case of the design of an information system that is based on a database, the conceptual data model is, at a later stage (usually called logical design), mapped to a logical data model, such as the relational model; this in turn is mapped to a physical model during physical design. Note that sometimes, both of these phases are referred to as "physical design".
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posted by Unknown @ 1:12 PM
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