188.8.131.52 Emitting Instruction for the Element Rule
Before emitting anything, the tool SHOULD determine whether there is an optional substitution that is NULL. If there is such a substitution, the tool MUST NOT emit anything for this element. The DependencyId rule (as specified in 2.2.12) determines whether there are any optional substitutions. If there are optional substitutions, the tool MUST emit the character "<" and the text, as specified by the Name rule (as specified in 2.2.12), as defined in the StartElement rule (also specified in 2.2.12). If the element contains array data (for more information, see section 184.108.40.206.5), the tool MUST emit multiple instances of the element, with one instance for each element of the array.