[xquery-talk] Tales of the unexpected version III - Atomization

[David Carlisle]

On 08/01/2014 11:11, Ihe Onwuka wrote:
>
>
>
> On Wed, Jan 8, 2014 at 11:03 AM, David Carlisle <davidc at nag.co.uk
> <mailto:davidc at nag.co.uk>> wrote:
>
>     On 08/01/2014 09:35, Ihe Onwuka wrote:
>
>               >
>               >  <person>{$thing/@name}</__person>
>
>
>         I can't begin to fathom the rationale for the exception or the
>         value of
>         such an exception over the simple rule of atomizing sequences if
>         they
>         appear in contexts where a value is expected.
>
>
>     why do you think an atomised value is expected here?
>
>
> because the value you put in an attribute must be atomic.......

If you add such a sequence in an attribute constructor then it is 
atomized, but here you are copying a sequence of nodes into an element 
constructor. In particular you are adding attribute nodes.

>
>     would you expect element nodes
>
>
>       <person>{$thing/name}</person>
>
>     to be atomised as well? (They aren't: this would add a sequence of
>     <name> children to <person>)
>
>
> ......and the value of an element doesn't have to be.

You are copying a sequence of nodes so that <person> becodes their 
parent, attribute and element nodes are treated similarly.

>
>
>
>      >  It seems to me that it is
>
>         just demanding the explicit call of the  data function (which is
>         exactly
>         what I put in) for something it could just have easily handled
>         implicitly.
>
>
>     But this construct is designed to add attribute nodes, so implicit
>     atomization would be undesirable.
>
>
> Why? It cannot be a placeholder for anything but an  atomic value.

No, as shown here it is copying attribute nodes. If $thing is

<foo name="me"/>

then

  <person>{$thing/@name}</person>

is

  <person name="me"></person>

but


  <person>{$thing/@name/string()}</person>

is

<person>me</person>

You are (I think) saying that atomization should be automatic and you 
should get the second result, but then you would not be able to copy 
attribute (or element) nodes.

David


>
>
>
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