​3.2​ IDs and References

The id property universally and uniquely identifies an SDO, SRO, Bundle, or Marking Definition. It MUST meet the requirements of the identifier type (see section 2.5).

All STIX Objects (as well as Bundle and Marking Definition) use identifiers as defined by the identifier type. The identifier type is also used to define properties that are ID references to other constructs (such as the created_by_ref property in all STIX Objects). _Resolving_an ID reference is the process of identifying and obtaining the actual object referred to by the ID reference property. ID references resolve to an object when the value of the ID reference property (e.g., created_by_ref) is an exact match with the id property of another object. If a consumer has access to multiple versions of an object, the consumer SHOULD interpret any references to that object as referring to the latest version as defined in section 3.4. ID references can refer to objects to which the consumer/producer may not currently have. This specification does not address the implementation of ID reference resolution.