SPARQL: arguments for built-in calls to generic?

Most of the built-in calls defined in the grammar in "[57] BuiltInCall"
operate on arguments of type Expression, which includes boolean and
mathematical operations. Most of these built-in calls, however, only
produce results when operating on IRIs, literals and/or blank nodes.
IMHO, it would be better to enforce this through the grammer, preventing
people from writing expressions that are correct syntactically, but not
semantically, like "lang( 3 + 4 )" and "isBlank(?var = foo:bar)".
Changing this production rule to the following should prevent such
expressions:

FunctionOrVar ::= IRIrefOrFunction | Var

BuiltInCall ::= 'STR' '(' FunctionOrVar ')'
               | 'LANG' '(' FunctionOrVar ')'
               | 'LANGMATCHES' '(' FunctionOrVar ',' String ')'
               | 'DATATYPE' '(' FunctionOrVar ')'
               | 'BOUND' '(' Var ')'
               | 'isIRI' '(' FunctionOrVar ')'
               | 'isURI' '(' FunctionOrVar ')'
               | 'isBLANK' '(' FunctionOrVar ')'
               | 'isLITERAL' '(' FunctionOrVar ')'
               | RegexExpression

RegexExpression ::= 'REGEX' '(' FunctionOrVar ',' String ( ',' String )? ')'


Considering that the spec is already in Last Call, I hope this comment
doesn't come too late.

Regards,

Arjohn

-- 
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