Not specified when entity sets that participate in a relationship set are distinct.
Clarification is needed only when the entity sets of a relationship set are not distinct.
The function that an entity plays in a relationship is called that entity’s role. RECURSIVE RELATIONSHIP When entities are self-linked then such a relationship is called a recursive relationship.
TOTAL PARTICIPATION The participation of an entity set E in a relationship set R is said to be TOTAL if every entity in E participates in at least one relationship in R. Student A ENTITY SET : STUDENT Student B Student B Mr A Mr B Mr B ENTITY SET : TEACHER RELATIONSHIP SET : SUBJECT
PARTIAL PARTICIPATION Mr A ENTITY SET : DEPARTMENT Mr B Mr B PB204 P2113 BBC101 ENTITY SET : COURSES RELATIONSHIP SET : COURSE The participation an entity set E in a relationship set R is said to be PARTIAL if only some entities in E participate in relationships in R.