Entity-Relationship Diagram (ERD)

Inside

What I Need to Get Started

Both ConceptDraw DIAGRAM diagramming and drawing software and the Entity-Relationship Diagram (ERD) solution can help creating the software engineering diagrams you need. The Entity-Relationship Diagram (ERD) solution can be found in the Software Development area of ConceptDraw STORE application that can be downloaded from this site. Make sure that both ConceptDraw DIAGRAM and ConceptDraw STORE applications are installed on your computer before you get started.

How to install

After ConceptDraw STORE and ConceptDraw DIAGRAM are downloaded and installed, you can install the Entity-Relationship Diagram (ERD) solution from the ConceptDraw STORE.

Start Using

To make sure that you are doing it all right, use the pre-designed symbols from the stencil libraries from the solution to make your drawings look smart and professional. Also, the pre-made examples from this solution can be used as drafts so your own drawings can be based on them. Using the samples, you can always change their structures, colors and data.

HelpDesk

How to Create an ERD Diagram

Entity-Relationship Diagrams

Creating an entity-relationship (ER) model is to visually represent the structure of a business database, where data equates to entities (or objects) that are linked by defined relationships expressing dependencies and requirements. By nature it is an abstract visualization, the first step in the design process towards creating a logical and functional database.

The original concept was formalized by Peter Chen, the influential computer scientist who wrote The Entity-Relationship Model – Towards a Unified View of Data. This paper provided structured notation for database models – it remains a well-used standard to this day, but other notations, such as Bachman, Barker, or Martin, have been devised to handle specific database requirements.

The Chen ERD notation, take from ConceptDraw’s Entity-Relationship Diagram solution

Entity-relationship diagrams (ERD) follow the common three-schema approach to software engineering, with three levels of abstraction being used to define an ER model.

Conceptual data model — A conceptual data model is the most abstract view of a data model. It offers a complete overview of a business area, including all significant business entities, and describing their relationships.

It omits further levels of detail, including data types and interface definitions, making it suitable as a means of presenting an initial business idea to a wide range of stakeholders.

Logical data model — Using this model a higher level of detail is established, with data entities describes as master, operational or transactional, and the relationships between them more precisely defined. This is the testing phase of a data model, where functionality can be observed independently of physical specifications.

An ERD showing entities with their primary keys, made using ConceptDraw DIAGRAM.

Physical data model — At this point data modellers start to take into account the physical constraints of the database area. Important factors to consider are database performance, physical storage space, and indexing strategy. Diagram notations will fully define all tables and columns, indexes, constrain definitions, and any linking or partitioned tables.

Creating an ERD requires choosing a specific set of notations that best serve the specific database being designed. Chen’s original notation had a linguistic approach, where boxes representing entities could be thought of as nouns, and the relationships between them were in verb form, shown on a diagram as a diamond.

Eventually Chen’s style was adapted into the crow’s foot notation, where relationships were shown as single labelled lines – this quickly became the popular standard, due to improved readability on diagrams, with a more efficient use of space on the page.

The crow’s foot ERD notation, take from ConceptDraw’s Entity-Relationship Diagram solution

Most other notation systems are adaptations, or use part of these original styles. Here is a brief list of some of the other standards that have been developed:

• Bachman notation
• Barker’s notation (ERDs for Oracle)
• EXPRESS and EXPRESS-G notation
• IDEFX1
• UML class diagrams
• Merise
• Object role modelling
• (min – max) notation

ERDs are an invaluable tool for software engineers, particularly since computing capacity, and thus data storage capacity, has markedly increased in recent years. They allow every aspect of database design to be managed, tested and communicated before implementation. Because ERDs have such a broad scope of influence across database activities, it’s imperative the standardized notation can be utilized and interpreted by a wide variety of stakeholders.

A model of a computer game server database, made with the ERD solution for ConceptDraw

To create an ERD, software engineers will mainly turn to dedicated drawing software, which will contain the full notation resources for their specific database design. CS Odessa has released an all-inclusive solution for their powerful drawing program, ConceptDraw DIAGRAM. The Entity-Relationship Diagram solution contains vector stencil image libraries with full standardized Chen and crow’s foot notation included. Added to the solution pack are a number of ERD templates and samples to help kick start users own ideas.

ConceptDraw DIAGRAM offers a number of features that make it the ideal system with which to create entity-relationship diagrams. Intelligent connectors are used to establish relationships – connecting lines that automatically map the best route to join diagram objects. One-click commands allow a diagram to be created efficiently, getting ideas on the page as quick as they arrive.

As with all ConceptDraw products, there is a large online resource of help material related to the Entity-Relationship Diagram solution, including video tutorials, how-to guides, and a host of help topics.