Message
mml @groupalign attribute must contain values from the list 'left', 'center', 'right', 'decimalpoint' grouped using { and } braces
Rule XPath:
This rule ASSERTS the following, raising an alert if FALSE:
not(@groupalign) or matches(@groupalign, '^(\{\s*(left|right|center|decimalpoint)(\s(left|right|center|decimalpoint))*\s*\}\s*)+$')