Cardinality
1) It represents the number of occurrences of one object related to number of occurrences of another object.
2) It gives maximum number occurrences in relationship.
3)Expected values are 1:1,1:M, M:N
4)E.g. many employees occupy one room.
Modality
1) A modality of relationship is zero if occurrence of relationship is optional and modality of relationship is 1 if occurrence of relationship is mandatory (i.e. compulsory).
2) The modality specifies the minimum number of relationships.
3)Expected values are 0 or 1
4)E.g. exactly one (maximum 1 and minimum 1) room is occupied by zero or many (maximum many and minimum 0) employees.
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