About Cardinality

Cardinality for a particular relationship definition specifies how many links can be created between records of the predecessor and successor families. Consider an example where the Has Maintenance relationship relates the Axial 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 Axial 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 Axial Compressor family is the predecessor and the Work Order family is the successor in the Has Maintenance relationship.

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

Note: The Many To Many cardinality is no supported for a Foreign Key Relationship.

Depending on the entity families and the relationship family involved in the relationship definition, some cardinality options may not be logical for your implementation. Via the Configuration Manager, administrative users can configure the cardinality between entity families according to your company's workflow.

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 when working with the records in the GE Digital APM. For example, if your system is configured such that a Work Order record can be linked to only one piece of equipment, such as a Pump, 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 prevents you from creating relationships that should not exist.

You can choose to allow only one link between the entities of the predecessor family and entities of the successor family within a given relationship definition. Multiple links, however, are allowed, if the predecessor or successor family participates in additional relationship definitions. For example, your system could be configured such that the each Work Order record can be linked to only one Equipment. If an additional relationship definition existed for the Work Order family and the Functional Location family, however, then a Work Order record could be linked to an Equipment record even if it was already linked to a Functional Location record.

Note: 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.