I cannot think of any way in the spec to specify the document URI of
a temporary in-memory tree, because I don't think that is meaningful
in the general case.
However, when I've chained transformations in the past, I've
sometimes needed to preserve the input document URI along all of the
steps (because there have been relative URI addresses in the data)
and so I've very simply used xml:base= on the document element of the
temporary tree (unless the document element already has an xml:base=
attribute).
Remember that from a syntax perspective, the root document file
entity of an XML document must contain the document element, so
base-uri(/*) is always the same as document-uri(root()) when there is
no xml:base= already there on the document element.
So, when I create a temporary tree I use:
<root xml:base="...whatever..."/>
... and when I ask for base-uri(/*) I get "...whatever...".
In my work I would do something along the lines of:
let $d := doc("input.xml") return
element {$d/name(.)}
{
attribute xml:base { "...whatever..." },
$d/@xml:base, (:in case there already exists one:)
"rest of the processing"
}
I hope this helps.
. . . . . . . . . . . Ken
At 2012-05-13 13:58 +0000, David Lee wrote:
I noticed somewhat of a hole in XQuery ... hoping I am wrong.
I can find no way to set the base URI of a constructed document e.g
document { <root/> }
such that fn:document-uri() would return it.
It seem this is one of those properties that must come from the
outside environment.
I know if I were to store the document to a file then re-read it,
likely the XML processor would pick it up ... I also know how to do
this programmatically in API's like say Saxon.
But it seems missing from XQuery itself. My guess is that since
XQuery doesnt support storing documents it was thought unimportant
to set the document URI.
Why I ask ?
I'm still looking at Streaming XDM formats, including pure in-memory
streaming.
But it seems like I cannot directly encode and pass on a document
(or base) URI through XQuery by itself to the output. So any
constructed documents would have none or undefined URI's to the
receiver. this leads me to think I need a meta encoding for XDM
much like proposed at Balisage (XDML). basically passing the URI
information as seperate XDM values and a convention for interpreting
them. This seems like it could not be done in pure XQuery however
because the target even if it got say a sequence ( "uri" , document
) has no way to apply the uri to the document using XQuery so it
must be done by external code.
Thanks for any commentary.
-David
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