1 Scope
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 EXTENDEDXER
encoding for specific ASN.1 types.