26324 2014-07-13 22:51:40 +0000 XQuery 3.0's PostfixExpr is not properly represented in XQueryX 3.0 2014-07-14 08:10:50 +0000 1 1 1 Unclassified XPath / XQuery / XSLT XQueryX 3.0 Recommendation All All CLOSED INVALID P2 major --- 1 jim.melton jim.melton mike public-qt-comments oldest_to_newest 108897 0 jim.melton 2014-07-13 22:51:40 +0000 In XQuery 3.0, the following expression is apparently valid: 12(1,2)[3] and is represented by the following BNF: PathExpr ::= ... | RelativePathExpr RelativePathExpr ::= StepExpr StepExpr ::= PostfixExpr | ... PostfixExpr ::= PrimaryExpr (Predicate | ArgumentList)* PrimaryExpr ::= Literal | ... (Note: I don't claim that I understand why anybody would write such an expression, but it is apparently valid.) The expressions is accepted by our syntax checker and produces the following parse tree: |START [1:0 - 1:10] | QueryList [1:0 - 1:10] | Module [1:0 - 1:10] | MainModule [1:0 - 1:10] | Prolog [1:0 - 0:0] | QueryBody [1:0 - 1:10] | Expr [1:0 - 1:10] | PathExpr [1:0 - 1:10] | PostfixExpr [1:0 - 1:10] | IntegerLiteral 12 [2:1 - 1:2] | ArgumentList [2:1 - 1:7] | Argument [2:3 - 1:4] | PathExpr [2:3 - 1:4] | PostfixExpr [2:3 - 1:4] | IntegerLiteral 1 [2:4 - 1:4] | Argument [2:5 - 1:6] | PathExpr [2:5 - 1:6] | PostfixExpr [2:5 - 1:6] | IntegerLiteral 2 [2:6 - 1:6] | Predicate [2:7 - 1:10] | Expr [2:8 - 1:9] | PathExpr [2:8 - 1:9] | PostfixExpr [2:8 - 1:9] | IntegerLiteral 3 [2:9 - 1:9] Note particularly the appearance of "PostfixExpr" in the parse tree. However, in the XQueryX translation produced by the syntax checker, that same expression transforms to: <?xml version="1.0"?> <xqx:module xmlns:xqx="http://www.w3.org/2005/XQueryX" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.w3.org/2005/XQueryX http://www.w3.org/2005/XQueryX/xqueryx.xsd"> <xqx:mainModule> <xqx:queryBody> <xqx:pathExpr> <xqx:stepExpr> <xqx:filterExpr> <xqx:dynamicFunctionInvocationExpr> <xqx:functionItem> <xqx:integerConstantExpr> <xqx:value>12</xqx:value> </xqx:integerConstantExpr> </xqx:functionItem> <xqx:arguments> <xqx:integerConstantExpr> <xqx:value>1</xqx:value> </xqx:integerConstantExpr> <xqx:integerConstantExpr> <xqx:value>2</xqx:value> </xqx:integerConstantExpr> </xqx:arguments> </xqx:dynamicFunctionInvocationExpr> </xqx:filterExpr> <xqx:predicates> <xqx:integerConstantExpr> <xqx:value>3</xqx:value> </xqx:integerConstantExpr> </xqx:predicates> </xqx:stepExpr> </xqx:pathExpr> </xqx:queryBody> </xqx:mainModule> </xqx:module> In this case, please note that the <xqx:functionItem> is an <xqx:integerConstantExpr> (12) followed by <xqx:arguments> (1 and 2). The XQueryX 3.0 stylesheet would (does) transform to the original expression: 12(1,2)[3] But that is more an accident than a planned chain of events. DOES THE XQUERYX COMMUNITY BELIEVE THAT THIS SHOULD BE "FIXED"? I presume that the fix would be to permit XQueryX code that looks something like this: <?xml version="1.0"?> <xqx:module xmlns:xqx="http://www.w3.org/2005/XQueryX" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.w3.org/2005/XQueryX http://www.w3.org/2005/XQueryX/xqueryx.xsd"> <xqx:mainModule> <xqx:queryBody> <xqx:pathExpr> <xqx:stepExpr> <xqx:postfixExpr> <xqx:integerConstantExpr> <xqx:value>12</xqx:value> </xqx:integerConstantExpr> <xqx:arguments> <xqx:integerConstantExpr> <xqx:value>1</xqx:value> </xqx:integerConstantExpr> <xqx:integerConstantExpr> <xqx:value>2</xqx:value> </xqx:integerConstantExpr> </xqx:arguments> </xqx:postfixExpr> <xqx:predicates> <xqx:integerConstantExpr> <xqx:value>3</xqx:value> </xqx:integerConstantExpr> </xqx:predicates> </xqx:stepExpr> </xqx:pathExpr> </xqx:queryBody> </xqx:mainModule> </xqx:module> (Note the use of <xqx:postfixExpr>, which does not appear at all in the XQueryX 3.0 schema or stylesheet.) I believe that I have no choice but to make this kind of fix in XQueryX 3.1 because of the new alternatives in the production for PostfixExpr, and I *think* (I'm still working on it) I can do so with full XQueryX 3.0 compatibility with or without "fixing" this problem in XQueryX 3.0. Guidance, please!! 108898 1 jim.melton 2014-07-13 23:31:31 +0000 Upon additional consideration, especially after re-reading XQuery 3.0, section 3.2 "Postfix Expressions", last paragraph: An expression (other than a raw EQName) followed by an argument list in parentheses (that is, E1(E2, E3, ...)) is referred to as a dynamic function call. Its effect is to evaluate E1 to obtain a function, and then call that function, with E2, E3, ... as arguments. Dynamic function calls are described in 3.2.2 Dynamic Function Call. I have concluded that the specific case of 12(1,2) is a useless artifact of allowing far more useful expressions such as $x(1,2) (which is a DynamicFunctionInvocation). The cost in "fixing" the case of 12(1,2) to be a (useless) Postfix Expression instead of a Dynamic Function Invocation is in no way worth the effort, particularly as it doesn't actually change any results. I am therefore marking this bug RESOLVED/INVALID and then marking it CLOSED. Sorry for the interruption. Please carry on. 108902 2 mike 2014-07-14 08:10:50 +0000 The expression 12(1) is syntactically valid but is always a type error (rather like the expression ("London"+1). So you're really asking a policy question: should XQueryX be able to represent every syntactically-valid XQuery expression, or should it only be required to represent expressions that have no static errors. (And then the sub-question, are type errors regarded as static errors for this purpose?)