These infoset members are needed to navigate back from an infoset element to the corresponding schema component. This is needed so as to access other annnotations (not DFDL annotations) on that schema component which may be needed by the application - enhanced diagnostic messages, etc. As an example, the units-of-measure of a numeric element may be stored on an appinfo annotation, but these may want to be used in error messages.

Implementing these requires implementing SCID (Schema Component Identifiers), and an API by which they can be used to access the schema component.