NBN ISO/IEC 8825-4:2021

This Recommendation | International Standard specifies a set of basic XML Encoding Rules (BASIC-XER) that may be
used to derive a transfer syntax for values of types defined in Rec. ITU-T X.680 | ISO/IEC 8824-1 and Rec. ITU-T
X.681 | ISO/IEC 8824-2. This Recommendation | International Standard also specifies a set of Canonical XML
Encoding Rules (CXER) which provide constraints on the basic XML Encoding Rules and produce a unique encoding
for any given ASN.1 value. This Recommendation | International Standard further specifies a set of extended XML
Encoding Rules (EXTENDED-XER) which adds further encoders options, and also allows the ASN.1 specifier to vary
the encoding that would be produced by BASIC-XER. It is implicit in the specification of these encoding rules that
they are also used for decoding.
The encoding rules specified in this Recommendation | International Standard:
– are used at the time of communication;
– are intended for use in circumstances where displaying of values and/or processing them using
commonly available XML tools (such as browsers) is the major concern in the choice of encoding rules;
– allow the extension of an abstract syntax by addition of extra values for all forms of extensibility
described in Rec. ITU-T X.680 | ISO/IEC 8824-1.
This Recommendation | International Standard also specifies the syntax and semantics of XER encoding instructions,
and the rules for their assignment and combination. XER encoding instructions can be used to control the EXTENDED-
XER encoding for specific ASN.1 types.