Construct an element by computing an expression.
A ComputedElementConstructor constructs an element by
computing the enclosed ExprSequence, called content
expression. The name of the element is either a QName or it
is computed from an expression (name expression).
The value resulting from evaluating the name expression undergoes
atomization, and must be a single atomic value of the type
xs:QName, xs:string, or
xdt:untypedAtomic, otherwise a type error is raised. If it is of
type xs:QName, its expanded QName is used as element name and the
prefix part of the QName is retained. Otherwise, the value is converted to an
expanded QName. If a namespace prefix is present, it is resolved using the
statically known namespaces, otherwise it is local in the default
namespace.
The content expression is evaluated in the same way as an enclosed
expression in an ElementConstructor.
Computed constructors may be nested and several constructors are separated by commas. Note how the expression sequence is evaluated for the nested element constructors:
for $a in input()/bib/book
return
element book {
element title { $a/title },
element notitle { "$a/title" }
}
This query is equivalent with the following one:
for $a in input()/bib/book
return
<book>
<title>{ $a/title }</title>
<notitle>{ "$a/title" }</notitle>
</book>
This query returns the alphabetical list of patient names grouped by the initial letter of the patients' surnames:
let $patients := input()/patient/name
let $letters := distinct-values(for $patient in $patients
return substring($patient/surname, 1, 1))
return
<patients> {
for $letter in $letters
return element { $letter } {
for $patient in $patients[substring(surname, 1, 1) = $letter]
order by $patient/surname
return $patient }
}
</patients>
Here, the name of the element is computed using the sequence of unique
letters resulting from the first nested FLWOR expression. The content
expression is another FLWOR expression returning the ordered list of all
name elements for all letters found.
The following construct(s) refer to this construct:
This construct is also related to the following construct(s):
ElementConstructor
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