The GCX XQuery Engine – Fragment XQ
For current GCX version 2.1 (v2.1)
Supported XQuery Fragment XQ:
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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.
Last updated: 2009-05-26
