owned and unowned relationships

What exactly is meant by owned and unowned relationships? These terms are often used in JPA/JDO documentation, but I haven't found a good definition of th开发者_运维技巧em.

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In addition to Nix's anwser, in JPA this term sometimes is used in different meaning - relationship is said to be owned by an entity if that entity is an owning side of the relationship, i.e. a side which defines the state of the relationship to be persisted.

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There tons of good definitions out there on Owned/Unowned Relationships.

Google App Engine Entity Relationships in JDO:

A relationship between persistent objects can be described as owned, where one of the objects cannot exist without the other, or unowned, where both objects can exist independently of their relationship with one another