Editing Data model (section)

=== Entity–relationship model ===
{{Main|Entity–relationship model}}
An entity–relationship model (ERM), sometimes referred to as an entity–relationship diagram (ERD), could be used to represent an abstract [[conceptual schema|conceptual data model]] (or [[semantic data model]] or physical data model) used in [[software engineering]] to represent structured data. There are several notations used for ERMs. Like DSD's, [[Attribute (computing)|attribute]]s are specified inside the entity boxes rather than outside of them, while relationships are drawn as lines, with the relationship constraints as descriptions on the line. The E-R model, while robust, can become visually cumbersome when representing entities with several attributes.

There are several styles for representing data structure diagrams, with a notable difference in the manner of defining cardinality. The choices are between arrow heads, inverted arrow heads (crow's feet), or numerical representation of the cardinality.