Components of ER Diagram

Entity-Relationship model gives the possibility to visually describe a database using the components of ER Diagram, entity relationship stencils, relationship symbols, work flow shapes. ER-diagram lets represent the data or entities, attributes of these entities and relationships between them, using standardized Crow’s Foot notation icons or Chen’s notation icons. An entity is an object of the real world, it can exist independently and has the instances which differ in attribute values (properties). The attributes give an unambiguous (uniquely) identification for the instance and are called the primary key, this key can be composite and combine several attributes. ConceptDraw DIAGRAM is a professional software available with Entity-Relationship Diagram (ERD) solution from Software Development area that lets create ERDs for various database systems, using Crow’s Foot and Chen’s notations. It is invaluable tool for software engineers and developers, it supports ODBC-compatible databases (Oracle, MySQL, MS Access, MS SQL, InterBase, Firebird and others).

Entity Relationship Diagram Symbols

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 DIAGRAM software.

Design Element: Chen for Entity Relationship Diagram - ERD

Entity-Relationship Diagrams (ERDs) were developed and introduced as a convenient and visual tool for the data modeling, they are the perfect way for easy determining data and also relationships between them. The first standard notation for ERD was proposed by Chen. Chen's notation is very rich on the data modeling tools and standard notation symbols and elements for drawing easy understandable Entity-relationship diagrams, Attribute diagrams, Decomposition charts, which are especially popular for designing relational databases. The entity is the main term, it is a set of instances abstract or real objects with common characteristics or attributes. Any system's object is represented by one uniquely identified entity, relationships describe the links between the entities. ConceptDraw DIAGRAM diagramming software, which includes the Entity-Relationship Diagram (ERD) solution, offers all needed tools for professional drawing ER diagrams. Specially developed vector ERD design elements according to Chen and Crow's Foot notations are indispensible for professional ERDs design.

Design elements - ERD (crow's foot notation)

"Crow's Foot notation is used in Barker's Notation, SSADM and Information Engineering. Crow's Foot diagrams represent entities as boxes, and relationships as lines between the boxes. Different shapes at the ends of these lines represent the cardinality of the relationship." [Entity–relationship model. Wikipedia]
The vector stencils library ERD, crow's foot notation contains 18 symbols for creating the ER-diagrams using the ConceptDraw PRO diagramming nd vector drawing software.
The example"Design elements - ERD solution (crow's foot notation)" is included in the Entity-Relationship Diagram (ERD) solution from the Software Development area of ConceptDraw Solution Park.

Crow's foot ERD

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Crow’s Foot Notation

ERD Symbols and Meanings

Entity Relationship Diagram (ERD) is a popular software engineering tool for database modeling and illustration the logical structure of databases, which uses one of two notations - Chen's or Crow’s Foot. Crow's foot notation is effective when used in software engineering, information engineering, structured systems analysis and design. Each of these notations applies its own set of ERD symbols. Crow's foot diagrams use boxes to represent entities and lines between these boxes to show relationships. Varied shapes at the ends of lines depict the cardinality of a given relationship. Chen's ERD notation is more detailed way to represent entities and relationships. ConceptDraw DIAGRAM application enhanced with all-inclusive Entity-Relationship Diagram (ERD) solution allows design professional ER diagrams with Chen's or Crow’s Foot notation on your choice. It contains the full set of ready-to-use standardized ERD symbols and meanings helpful for quickly drawing, collection of predesigned ERD samples, examples and templates. ConceptDraw Pro is a great alternative to Visio for Mac users as it offers more features and can easily handle the most demanding professional needs.

How to Build an Entity Relationship Diagram (ERD)

Design Element: Crows Foot for Entity Relationship Diagram - ERD

Entity-Relationship Diagram (ERD) is ideal tool that helps execute the detalization of data warehouse for a given designed system, lets to document the system's entities, attributes (objects' properties), and their interactions each other (relationships). Creation of an ERD requires the choice of specific set of notations, which the best suits for your database design. Two notations - Chen’s and Crow's Foot are applied for ERDs design. Chen's notation was developed first and has linguistic approach, the boxes represent the entities and are considered as nouns, relationships between them are shown as diamonds in a verb form. Over time Chen’s style was adapted into the popular standard - Crow’s Foot notation, where entities are shown as boxes and relationships - as labeled lines. ConceptDraw DIAGRAM software supplied with Entity-Relationship Diagram (ERD) solution offers samples and templates of ER diagrams, and also ready-to-use vector design elements - ERD Crow′s Foot and Chen's notation icons for easy designing your own ER diagrams for depicting databases.

Entity Relationship Diagram - ERD - Software for Design Crows Foot ER Diagrams

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 DIAGRAM. 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.

How to Build an Entity Relationship Diagram (ERD)

Entity Relationship Diagram - ERD - Software for Design Chen ER Diagrams

The Entity-Relationship Diagram (ERD) solution from ConceptDraw Solution Park extends ConceptDraw DIAGRAM ector graphics and diagramming software with the ability to describe a database using the Entity-Relationship (Chen) model. Use it for design your ERDs and verify that ConceptDraw DIAGRAM offers the best ERD diagrams software tools for design element Chen notation.

Entity Relationship Diagram Software Engineering

Entity Relationship Diagram (aka ER Diagram, E-R Diagram, ERD) is a time-tested and widespread software development and software engineering method for data modeling, illustrating the logical structure of databases and system design. For ERDs construction are used three basic elements: entities, attributes, and relationships. Chen's notation for ERD supposes the use of rectangles (boxes) to represent entities and diamonds to depict relationships between first-class objects. This notation is popular when creating conceptual data models of information systems. Another standardized notation for ER diagrams is Crow's foot notation. ConceptDraw DIAGRAM as a powerful Entity Relationship Diagram software engineering provides the tools of Entity-Relationship Diagram (ERD) solution from Software Development area of ConceptDraw Solution Park for instantly describing databases using ERDs of Crow’s Foot and Chen’s notations. Use the predesigned vector elements for both these notations from 2 libraries included to Entity-Relationship Diagram (ERD) solution.

Design elements - ER diagram (Chen notation)

"Chen's notation for entity–relationship modeling uses rectangles to represent entity sets, and diamonds to represent relationships appropriate for first-class objects: they can have attributes and relationships of their own. If an entity set participates in a relationship set, they are connected with a line.
Attributes are drawn as ovals and are connected with a line to exactly one entity or relationship set.
Cardinality constraints are expressed as follows:
- a double line indicates a participation constraint, totality or surjectivity: all entities in the entity set must participate in at least one relationship in the relationship set;
- an arrow from entity set to relationship set indicates a key constraint, i.e. injectivity: each entity of the entity set can participate in at most one relationship in the relationship set;
- a thick line indicates both, i.e. bijectivity: each entity in the entity set is involved in exactly one relationship.
- an underlined name of an attribute indicates that it is a key: two different entities or relationships with this attribute always have different values for this attribute.
Attributes are often omitted as they can clutter up a diagram; other diagram techniques often list entity attributes within the rectangles drawn for entity sets." [Entity–relationship model. Wikipedia]
The vector stencils library ERD, Chen's notation contains 13 symbols for drawing entity-relatinship diagrams using the ConceptDraw PRO diagramming and vector drawing software.
The example "Design elements - ER diagram (Chen notation)" is included in the Entity-Relationship Diagram (ERD) solution from the Software Development area of ConceptDraw Solution Park.

Chen's ERD

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Chen Notation

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