【71】
An（71）is a detailed, logical, graphical tool for modeling data.Each entity type should have an（72）, an attribute or a combination of attributes whose value distinguishes individual instances of the entity type.The（73）of a relationship is the number of entity types that participate in it.A（74）relationship is a relationship between the instances of a single entity type.An（75）entity is an entity type that associates the instances of one or more entity types and contains attributes peculiar to that relationship.
