Cardinality

Cardinality specifies, for a particular relationship definition, how many links can be created between records of the predecessor and successor families. Consider an example where the Has Maintenance relationship relates the Compressor family to the Work Order family. Within this relationship definition, the cardinality would specify how many Work Order records could be linked to a given Compressor record, and vice versa.

The following list provides descriptions of the cardinality rules that can be defined for successors and predecessors. For the purposes of our examples, assume that the Compressor family is the predecessor and the Work Order family is the successor in the Has Maintenance relationship.

One and only one predecessor record can be linked to one and only one successor record. For example, one and only one Compressor record can be linked to one and only one Work Order record. Compressor A can be linked to Work Order 1, but Compressor A cannot be linked to any other Work Orders.
One and only one predecessor record can be linked to many successor records. For example, one and only one Compressor record can be linked to many Work Order records. Compressor A can be linked to Work Order 1, Work Order 2, and Work Order 3, and so on.
Many predecessor records can be linked to one and only one successor record. For example, many Compressor records can be linked to one and only one Work Order record. Compressor A and Compressor B could be linked to Work Order 1.
Many predecessor records can be linked to many successor records. For example, many Compressor records can be linked to many Work Order records. Compressor A and Compressor B can be linked to Work Order 1, and Compressor A and Compressor B can be linked to Work Order 2.

Based on the cardinality defined between entity families through a given relationship family, you will be limited to the number of links that you can create between records. For example, if your system is configured such that a Work Order record can be linked to only one Pump record, you could create a link between Pump 101 and Work Order 1, but you could not link Work Order 1 to any other records. If you tried to do so, GE Digital APM would generate an error. In this way, cardinality helps you maintain integrity in your database because it prevents you from creating relationships that should not exist.

A given family can also act as the predecessor in one relationship and the successor in another. For example, the Equipment family is the successor in the Functional Location Has Equipment relationship and the successor in the Equipment Has Equipment relationship.