Entity-Relationship Diagram - Overview

E/R diagrams are bipartite graphs used to describe value range structures or topic diagrams. Value range structures describe observable values at locations within the system whereas topic diagrams allow a much wider usage in order to cover all correlations between interesting points. The main elements of an ER diagram are entity sets and relations among them.

Entity Sets

Entities are objects or things that can be identified. Entities are classified into different Entity sets. Sets of entities participate in relations.

			Entity Set
			L-Entity Set
			U-Entity Set
			Structure Entity Set
			Partition

Relations

Relations describe relationships between entities.

			Relation
			1:n Relation
			1:1 Relation
			1:n Relation Symbol
			1:1 Relation Symbol

Edges

Edges connect entity sets and relations.

Edge direct, horizontal & vertical (Note: the horizontal and vertical shapes are both of the same auto-layout type, only having a different initial state)

Curved Edge

Static L,S Edge horizontal, vertical

Binary Relations

Binary Relations are the most common relationships as two entities participate in the relation.

Binary Relation direct, horizontal & vertical (Note: the horizontal and vertical shapes are both of the same auto-layout type, only having a different initial state)

Curved Binary Relation horizontal, vertical

Shared

These masters are part of all stencil sets, not only ER Diagram.

			Dots
			Brace
			Annotation
			Title Block
			Frame & Title Block