[xsl] [XPath 3.0] Why should I bother specifying the "arity" of a function that I invoke?

["Costello, Roger L." <costello@xxxxxxxxx>]

Hi Folks,

The XPath 3.0 specification says that when a named function is invoked you
should specify the number of arguments (i.e., the arity):

	NamedFunctionRef 	   ::=    	EQName "#" IntegerLiteral

Here is an example:

   	concat#3('Section', ': ', 1)

But this works just as well:

	concat('Section', ': ', 1)

So why should I bother specifying the arity? Is there a case where I *must*
specify the arity?

/Roger