Partitionary

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A partitionary system is one where the divisions between headmates are particularly solidly defined. This may include other attributes, like lack of memory sharing, lack of internal communication, or lack of co-consciousness and resulting time loss.

Systems may become more or less partitionary over time. It is also possible for different headmates to have different levels of partitioning from the rest of the system or subsystem.

Related Terms
A system with fluidly defined divisions could be a median system.

Amnesiac systems are a related concept which have limited memory sharing or internal communication.

Traumagenic systems and DID systems are often partitionary.