This part of ISO/IEC 21000 specifies the syntax and semantics of tools that may be used to assist the
adaptation of Digital Items, i.e., the Digital Item Declaration and resources referenced by the declaration. The
tools could be used to satisfy transmission, storage and consumption constraints, as well as Quality of Service
management by the various Users. It is important to emphasize that the adaptation engines themselves are
non-normative tools of this part of ISO/IEC 21000.