ER-model is a data model which lets describe the conceptual schemes in a specific subject area. It can help to highlight the key entities and specify relationships that can be established between these entities. During the database design, it is realized the transformation of ER model into certain database scheme based on the chosen data model (relational, object, network, etc.). There are used two notations for ERDs: Crow's Foot and Chen's.
Crow's Foot notation proposed by Gordon Everest represents the entity by rectangle containing its name (name must be unique within this model), and relation - by the line which links two entities involved in relationship. The relationship's plurality is graphically indicated by a "plug" on the end of the link, the optionality - by a circle. Entity-Relationship Diagrams based on Crow's Foot notation can be easily drawn using the ConceptDraw PRO. Extended with Entity-Relationship Diagram (ERD) solution, it is the best ERD diagrams software with powerful tools and ready design elements for Crow's Foot and Chen notations. Read more
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The semantic modeling method nowadays is successfully applied in database structure design. It is effective method of modeling the data structures, which is based on the meaning of these data. As a tool of semantic modeling, there are used different types of Entity-Relationship Diagrams. Entity Relationship Diagram (ERD) is applied to visually and clearly represent a structure of a business database. The main components of ERDs are: entity, relation and attributes. An entity is a class of similar objects in the model, each entity is depicted in the form of rectangle and has the name expressed by a noun. Relation is shown in the form of non-directional line that connects two entities. There are several notation styles used for ERDs: information engineering style, Chen style, Bachman style, Martin Style.
The Entity Relationship Diagram symbols used for professional ERD drawing are predesigned by professionals and collected in the libraries of the Entity-Relationship Diagram (ERD) solution for ConceptDraw PRO software. Read more