DICOM PS3.3 2021e - Information Object Definitions
A. Relationship Constraints

Relationships between Content Items in the content of this IOD may be conveyed either by-value or by-reference. Table A.35.15-2 specifies the relationship constraints of this IOD. See Table C.17.3-8 for Relationship Type definitions.

Table A.35.15-2. Relationship Content Constraints for Extensible SR IOD

Source Value Type

Relationship Type (Enumerated Values)

Target Value Type



any type

any type

any type other than CONTAINS

any type


The lack of explicit constraints between value types and relationship types is necessary to support extensibility in unanticipated ways (e.g., to support new coordinate value types that may be selected from new composite object value types), but that does not mean that all possible combinations will make sense or be usable (e.g., HAS OBS CONTEXT with source and target value types of IMAGE).

Relationships by-reference to ancestor Content Items are forbidden in this IOD to prevent loops.

DICOM PS3.3 2021e - Information Object Definitions