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. - a thick line indicates both, i.e. bijectivity: each entity in the entity set is involved in exactly one relationship.
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 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: one-to-one,
"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.
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.
Object-role Modeling (ORM) Diagram solution with powerful vector diagramming and data modeling tools, large quantity of specially developed samples and examples, and rich variety of vector objects corresponding to common ORM notation, ideally suits for developing the comprehensive, clear and visual Object-role Modeling (ORM) diagrams and schematics, understandable for all interested people from the different fields and business directions, for designing the ORM models, and demonstrating advantages from the use of ORM and its notation. It is intended for software developers and computer engineers, specialists in a field of Object-oriented programming (OOP), database architects, web-application constructors and developers, etc.