XML Encoding Rules
XML Encoding Rules (XER), defined in ITU-T standard X.693, are a set of ASN.1 encoding rules for producing an XML-based verbose textual transfer syntax for data structures described in ASN.1.
XER allows some flexibility with respect to, for example, white-space characters between XML elements. A variant of XER called Canonical XML Encoding Rules (CXER) is also defined for uses where encodings have to be deterministic, such as security exchanges. Data encoded in CXER is always valid XER, but not vice versa.