2.2.11 r Extensions
The r element specified in [ISO/IEC29500-1:2016] section 17.3.2.25 is extended by the addition of the symEx element (section 2.7.1.1).<10> To maintain compatibility with ISO/IEC-29500 implementations, the prefix of the element namespace MUST be specified in an Ignorable attribute ([ISO/IEC29500-3:2015] section 7.2).