Records are assigned values from attributes. An assignment indicates that a record has a value from an attribute.
A record typically has assignments from multiple attributes. For each assigned attribute, the record may have one or more values. An assignment on an attribute is known as a key-value pair (KVP).
Not all attributes will have an assignment for every record. For example, for a publisher that sells both books and magazines, the ISBNnumber attribute would be assigned for book records, but not assigned (empty) for most magazine records.
Attributes may be single-assign or multi-assign:
By default, all attributes are single-assign. To make an attribute multi-assign, you must update the attribute configuration.