OSys-XER differs from (BASIC-)XER in the following ways:
Lists of numbers, enumerated tokens, and named bits are expressed in space-separated list form instead of as individually wrapped elements or value lists.
For example, the ASN.1 specification “A ::= SEQUENCE OF INTEGER” with value “{ 1 2 3 }” would produce the following encoding in XER:
<A><INTEGER>1</INTEGER><INTEGER>2</INTEGER><INTEGER>3</INTEGER></A>
in XML, it would be the following:
<A>1 2 3</A>
The values of the BOOLEAN data type are expressed as the lower case words “true” or “false” with no delimiters. In XER, the values are <true/> and <false/>.
Enumerated token values are expressed as the identifiers themselves instead of as empty XML elements (i.e. elements wrapped in ‘< />’). For example, a value of the ASN.1 type “Colors ::= ENUMERATED { red, blue, green }” equal to “red” would simply be “<color>red</color>” instead of “<color><red/></color>”.
The special REAL values <NOT-A-NUMBER/>, <PLUS-INFINITY/> and <MINUS-INFINITY/> are represented as NaN, INF and -INF, respectively.
GeneralizedTime and UTCTime values are transformed into the XSD representation for dateTime (YYYY-MMDDTHH: MM:SS[.SSSS][(Z|(+|-)HH:MM)]) when encoded to XML. When an XML document is decoded, the time format is transformed into the ASN.1 format.