The GCX XQuery Engine – Fragment XQ

For current GCX version 2.1 (v2.1)

Supported XQuery Fragment XQ:
–––––––––––––––––––––––––––––
          XQuery ::= (CommentExpr)? XMLExpr
     CommentExpr ::= (: [CommentExpr]∗ String [CommentExpr]∗ :)
         XMLExpr ::= <QName> NestedXMLExpr </QName>
                    | <QName></QName> | <QName/>
   NestedXMLExpr ::= {QExpr} | String | XMLExpr | NestedXMLExpr NestedXMLExpr
           QExpr ::= ReturnQExpr | QExpr, QExpr
     ReturnQExpr ::= QExprSingle | (QExpr) | ()
     QExprSingle ::= "String" | Numeric | FWRExpr | IfExpr | VarExpr
                    | AggregateFunct | RoundingFunct | NestedXMLExpr
         FWRExpr ::= ForClause [where Condition]? return ReturnQExpr
       ForClause ::= for $VarName in VarExpr [, $VarName in VarExpr]∗
          IfExpr ::= if (Condition) then ReturnQExpr else ReturnQExpr
       Condition ::= VarExpr | fn:true() | fn:false() | fn:exists(VarExpr)
                    | fn:empty(VarExpr) | fn:not(Condition)
                    | (Condition) | Condition and Condition
                    | Condition or Condition | Operand RelOp Operand
         Operand ::= VarExpr | AggregateFunct | RoundingFunct
                    | "String" | Numeric
           RelOp ::= < | <= | >= | > | = | !=
  AggregateFunct ::= fn:sum(VarExpr) | fn:avg(VarExpr)
                    | fn:min(VarExpr) | fn:max(VarExpr)
                    | fn:count(VarExpr) | fn:stddev_samp(VarExpr)
                    | fn:stddev_pop(VarExpr) | fn:var_samp(VarExpr)
                    | fn:var_pop(VarExpr) | fn:median(VarExpr)
   RoundingFunct ::= fn:abs(AggregateFunct) | fn:ceiling(AggregateFunct)
                    | fn:cover(AggregateFunct) | fn:floor(AggregateFunct)
                    | fn:round(AggregateFunct) | fn:truncate(AggregateFunct)
                    | fn:round–half–to–even(AggregateFunct)
         VarExpr ::= $VarName | VarAxisExpr
     VarAxisExpr ::= $VarName PathExpr | PathExpr | DocPathExpr
     DocPathExpr ::= fn:doc("FileName") | fn:doc("FileName") / PathStepExpr
        PathExpr ::= (/) | / | PathStepExpr
    PathStepExpr ::= Axis NodeTest | Axis NodeTest / PathStepExpr
            Axis ::= / | /child:: | // | /descendant::
        NodeTest ::= node() | text() | ∗ | QName

           QName ::= tagname
          String ::= string constant
         Numeric ::= numeric constant
         VarName ::= variable name
        FileName ::= file name

Note: The fn:doc() construct (cf. rule DocPathExpr) fixes the input document;
all absolute paths in the query will be bound to this document and will
override xml input stream specification from command–line (such as ––xml).
When fn:doc() is used multiple times, GCX expects all occurrences to contain
the same document, i.e. input from multiples documents at a time is currently
not supported.