XQuery中=>語法的含義是什麼？

Question

在進行考試練習時，遇到麻煩的是瞭解XML中的「=>」語法。搜索它的網頁，但無法找到它的意義。以下是使用語法的考試範例：

FOR $b IN //Brand 
LET $cars := 
    (FOR $c IN //Car 
    LET $cb := $c/@model => //Model/.. 
    WHERE $cb/@name = $b/@name 
    RETURN $c) 
LET $nr := COUNT($cars) 
RETURN <Brand name={$b/@name}>{$nr}</Brand> 

它的目標是統計每個品牌的所有汽車。

這是我嘗試：

FOR $b IN //Brand 
LET $cars := (
    FOR $c IN //Car 
    WHERE $c/@Model = $b/Model/@name //Might not work to match against all models this way? 
    RETURN ({c}) 
RETURN <Brand name={$b/@name}>COUNT($cars)</Brand> 

這是XML文檔：

<!DOCTYPE CarsNStars [ 
<!ELEMENT CarsNStars (Brand*, Car*)> 
<!ELEMENT Brand (Model*)> 
<!ELEMENT Model (Year+)> 
<!ELEMENT Year (#EMPTY)> 
<!ELEMENT Car (#EMPTY)> 
<!ATTLIST Brand 
    name ID #REQUIRED 
    country CDATA #IMPLIED> 
<!ATTLIST Model 
    name ID #REQUIRED> 
<!ATTLIST Year 
    year CDATA #REQUIRED 
    horsePower CDATA #IMPLIED> 
<!ATTLIST Car 
    regNr ID #REQUIRED 
    model IDREF #REQUIRED 
    miles CDATA #REQUIRED> 
]> 

編輯時的地方，這顯然必須已經從講師一個錯字。

Answer 1

語法=>未在任何XQuery規範（1.0或3.0）中定義。 WHEN也不是。