Architecting and designing : Data modeling : Components of an entity relation diagram : Objects in an ERD : Relation lines
  
Relation lines
Relationships correspond to foreign key constraints in the physical data model. There are three different types of lines possible in a logical model: one for parent/child relations (Identifying and Nonidentifying), one for Super-sub relations, and one for Non-specific relations.
Definition properties for the three different types of relation lines are slightly different.
Relation lines may be named, but names are not required. The fully qualified name for a relationship definition is:
<relation name>.<source entity>.<target entity>.<model name>
where:
▪relation name is the name you provided when drawing the line
▪source entity is the name of the parent entity/supertype/source entity
▪target entity is the child entity/subtype/target entity
▪model name is the name of the Project Model.
See also
Defining super-sub (ERD) or categorization (IDEF1X) relationships
Defining identifying and nonidentifying relations
Defining non-specific relations
Deleting relation lines from diagrams
Consistency checks applied during relation line placement
Roles
Triggers
Objects in an ERD