rng-in-attribute-regex

rng-in-attribute-regex is a variable defined in `rng-nxml.el'.
Its value is

"<\\(?:[_[:alpha:]][-._[:alnum:]]*\\)\\(?::\\(?:[_[:alpha:]][-._[:alnum:]]*\\)\\)?\\(?:[ 	
\n]+\\(?:[_[:alpha:]][-._[:alnum:]]*\\)\\(?::\\(?:[_[:alpha:]][-._[:alnum:]]*\\)\\)?[ 	
\n]*=[ 	
\n]*\\(?:\"[^\"]*\"\\|'[^']*'\\)\\)*[ 	
\n]+\\(\\(?:\\(?:[_[:alpha:]][-._[:alnum:]]*\\)\\(?::\\(?:[_[:alpha:]][-._[:alnum:]]*\\)?\\)?\\)?\\)\\="

• This variable may be risky if used as a file-local variable.

Documentation:
Not documented as a variable.