The concept of extensibility implies that a recipient may encounter Content Items, Value Types and Relationship Types that are unanticipated and unsupported and hence potentially unrenderable.

An implementation shall identify in its Conformance Statement which Content Items, Value Types and Relationship Types it supports.

Since it may not be possible to render the entire content in an unambiguous manner because of unrecognized content, an SCP intending to display or otherwise render an Extensible SR SOP Instance