Entity-Relationship Diagram (ERD)
with ConceptDraw DIAGRAM
Entity-Relationship Diagram (ERD) serves for detailed description of structures and databases. An ERD represents a diagram made up mainly of rectangular blocks (for entities, or data) linked with relationships. The links between the blocks describe relations between these entities. There are three types of relationships:
For example, "driver drives a car". Here, the entity "driver" relates to the entity "car" by means of a one-to-one relationship "drives". One driver drives one car.
An example of a one-to-many relationship is a sergeant commanding a team of soldiers. Here the entity "sergeant" relates to a number of entities "soldier" by means of a one-to-many relationship.
Since the many-to-many relationship does not adequately represent the nature of interaction between entities, it is rarely used in diagrams, or is used in diagrams with little detail.
Entities and relationships can both have attributes. Example: a car from the first example has number; the "drives" relation may have quality attributes describing the quality of driving, or time attributes, saying when exactly the driver was driving the car.
ERDs are mainly used to describe database structures, though they might be used as diagrams describing a structure of a company, organization, or some business processes.
ConceptDraw DIAGRAM extended with Entity-Relationship Diagram (ERD) solution from the Software Development Area allows you to draw very complex and detailed ERD. It has a number of libraries with objects used in diagrams, which are included in relevant templates and samples available from ConceptDraw STORE.
Example 1. Entity-Relationship Diagram (ERD) Solution in ConceptDraw STORE
In actual practice, ERDs employing the method of P.P. Chen are used most. Choose the Chen ERD template in ConceptDraw STORE. A new document will open along with the library with objects necessary to create a diagram. Drag the vector objects representing entities and relationships, and then just connect them between each other in the required order. Use respective library objects to indicate the types of relationships and their attributes.
Example 2. ERD WordPressFile Reference. Chen's Notation
One of advantages of ERD diagram drawn in ConceptDraw DIAGRAM is that when you move entities on the diagram, they stay connected and you don't need to move relationships too.
Apart from building a diagram manually, ConceptDraw has a built-in tool for drawing an ERD automatically, from a database.
Example 3. Entity Relationship Model Diagram. Crow's Foot Notation
The samples you see on this page were created in ConceptDraw DIAGRAM using the Entity-Relationship Diagram (ERD) Solution and demonstrate some of solution's capabilities and the results you can achieve.
All source documents are vector graphic documents. They are available for reviewing, modifying, or converting to a variety of formats (PDF file, MS PowerPoint, MS Visio, and many other graphic formats) from the ConceptDraw STORE. The Entity-Relationship Diagram (ERD) Solution is available for all ConceptDraw DIAGRAM or later users.
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A model of a system is defined as a set of hierarchical diagrams representing the asynchronous process of data transformation from the moment it is input to the system to the moment it is output to the user. To demonstrate how a process transforms the initial data, you should design a data flow diagram using a DFD Library included in ConceptDraw DIAGRAM Solution Park. Start your diagramming experience now!
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A database is a data collection, structured into some conceptual model. Two most common approaches of developing data models are UML diagrams and ER-model diagrams. There are several notations of entity-relationship diagram symbols and their meaning is slightly different. Crow’s Foot notation is quite descriptive and easy to understand, meanwhile, the Chen notation is great for conceptual modeling.
An entity relationship diagrams look very simple to a flowcharts. The main difference is the symbols provided by specific ERD notations. There are several models applied in entity-relationship diagrams: conceptual, logical and physical. Creating an entity relationship diagram requires using a specific notation. There are five main components of common ERD notations: Entities, Actions, Attributes, Cardinality and Connections. The two of notations most widely used for creating ERD are Chen notation and Crow foot notation. By the way, the Crow foot notation originates from the Chen notation - it is an adapted version of the Chen notation.
Picture: ERD Symbols and Meanings
Job duties in small companies are usually spread randomly among workers, causing lots of problems and misunderstanding. One of the ways to restore order in business processing is to create a cross-functional flowchart with swim lanes that would represent every step in production system. Another advantage of using swim lanes flowchart is that it represents not only processes, but people responsible for them.
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Picture: Swim Lane Diagrams
Database design is an important part of any project, as databases become more and more complex nowadays. To make the model more representative, entity relationship diagrams are widely used in software engineering area. These diagrams show sets of entities as rectangles connected via lines labeled with their cardinalities.
This an example of the ER-diagram developed to store information regarding some online role-playing game. It includes three main elements of ER diagram: entities, relationships and attributes. The entities, attributes and relationships on this ER-diagram is depicted according to the Chen's notation. Chen's notation for Entity Relationship diagrams admits using of rectangles to depict entities, ovals for attributes and ,at least, diamonds to show relationships. ConceptDraw Entity-Relationship Diagrams solution was applied as ERD software to create this diagram.
Picture: ConceptDraw DIAGRAM ER Diagram Tool
Entity Relationship Diagram (ERD) is the world-known way to show the logical structure of databases in visual manner. The best software tool for drawing Entity-Relationship Diagram is ConceptDraw DIAGRAM vector graphics software with Entity-Relationship Diagram (ERD) solution from Software Development area which gives the ability to describe a database using the Entity-Relationship model. The vector graphic diagrams produced using this solution can be successfully used in whitepapers, presentations, datasheets, posters, or any technical materials.
Picture: Entity-Relationship Diagram