XPath expressions in Orbeon

Hi,

XForms officially uses XPath 1.0. This seems rather unexpressive.

I'd like to express things like

('foo' was chosen in mylistbox AND ((an integer below 18 was entered in
myinputfield AND mycheckbox was true) OR myinputfield has not been
filled in yet)

(just making something up here, ad-hoc pseudocode). I heard OPS can use
XPath 2 instead of XPath 1 - does this mean I could specify expressions
like that for the "relevant" attribute of XForms elements when I used
OPS? Does anyone by chance know nice examples of more complex XPath
expressions like this?


Kind regards,

Arnout



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Arnout Engelen schreef:
> I'd like to express things like ('foo' was chosen in mylistbox AND
> ((an integer below 18 was entered in myinputfield AND mycheckbox was
> true) OR myinputfield has not been filled in yet)
On a related note: how can I add additional namespaces (like  
xmlns:fn="http://www.w3.org/2005/xpath-functions") to the XPath Sandbox?


Arnout



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Arnout,

The most useful aspects of XPath 2.0 IMO are the if() and for()
constructs, support for types (even simple types are very useful), and
the vastly expanded function library.

Some of our examples use XPath 2.0 expressions, in particular we use
XPath 2.0's if() construct instead of the XForms 1.0 if() function.

The condition you express below can, BTW, be expressed with XPath 1.0
and the extension if() function: it is not a particularly difficult one.
But XPath 2.0 makes it easier to check on the integer, and I would go
about it like this:

<instance>
   <listbox/>
   <myinputfield/>
   <mycheckbox/>
</instance>

listbox = 'foo' and ((myinputfield castable as xs:integer and mychebox =
'true') or myinputfield = '')

Google will find for you articles about XPath 2.0, for example:

   http://www.developer.com/xml/article.php/3344421

Also, the spec is of course your friend:

   http://www.w3.org/TR/xpath20/

as is Michael Kay's book:

   http://www.amazon.com/gp/product/0764569104/

-Erik

Arnout Engelen wrote:
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Orbeon - XForms Everywhere:
http://www.orbeon.com/blog/



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Arnout Engelen wrote:

> On a related note: how can I add additional namespaces (like  
> xmlns:fn="http://www.w3.org/2005/xpath-functions") to the XPath Sandbox?

I don't think you can with the current XPath Sandbox.

This said, you don't need to add the namespace above to use the XPath
function library.

-Erik

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