RE: validating an xform

[John Boyer]

And further to John Clark's point, I would think that if you omitted the resource child element, resource attribute and action attribute, then you would get an xforms-submit-error with error-type of resource-error.  But in the processing model, we obtain the submission resource only after the validation check has been done.  So, you only get the resource-error if the validation succeeds, and you get the validation-error otherwise.

The specification indicates that omission of the resource is an error, but it unfortunately does not dot-the-i and mention generation of xforms-submit-error with error-type of resource-error as the way of reporting that error, but this seems to be just an editorial omission which I propose herewith that the editor should fix. :-)

John M. Boyer, Ph.D.
STSM, Interactive Documents and Web 2.0 Applications
Chair, W3C Forms Working Group
Workplace, Portal and Collaboration Software
IBM Victoria Software Lab
E-Mail: boyerj@...  

Blog: http://www.ibm.com/developerworks/blogs/page/JohnBoyer
Blog RSS feed: http://www.ibm.com/developerworks/blogs/rss/JohnBoyer?flavor=rssdw

From:	"Clark, John" <CLARKJ2@...>
To:	xforms <www-forms@...>
Date:	11/25/2008 06:44 AM
Subject:	RE: validating an xform

---

In addition to Erik's observation, you can use XForms submissions to perform arbitrarily powerful validations (or other types of processing) on the server, without navigating away from the current form.  The key to doing this uses `replace="instance"` as well as the `instance` and `target` attributes, which specify which instance and node should be replaced, respectively.  This means that remote service should return XML, which is then spliced into the target node in the instance specified, as you would expect.  (By default, a submission uses `replace="all"`, which will replace the entire page with the result data from the submission, which is likely the behaviour that you're experiencing now.)  This might look like:

 <xf:submission id="validate"
   resource="http://example.org/path/to/validation/service"
   method="post" ref="instance('data-to-validate')"
   replace="instance" instance="validation-results" target="/*"/>

Of course, you can definitely combine client-side validation with server-side validation in a natural way.  We do this in our application.  We have an array of type checks on fields that are implemented using model item properties (applied with `xf:bind` elements), and then we submit to a server process to do more complex validation, currently implemented in Schematron.  The Schematron validator then returns SVRL (an XML dialect for describing Schematron validation results, see <http://www.schematron.com/validators.html>), which the form can then use to inform the user about the result of validation.

Let us know if this doesn't give you enough information to move forward.

Take care,

   John L. Clark


-----Original Message-----
From: www-forms-request@... on behalf of Erik Bruchez
Sent: Tue 11/25/2008 2:48 AM
To: xforms
Subject: Re: validating an xform


> I'm new to the list. I'd like to ask your help to clarify some things
> because I don't know what is the best practice for my issues. The
> problem is the following: I have an xform where input widgets can have
> some constraints (e.g. a field can only accept integers from an
> interval, or some fields are required, etc.). How to check if the form
> satisfies these constraints?
> (1) Should it be done on the client side with JavaScript? or

In XForms, you often validate without JavaScript! See for example:

  <xforms:bind nodeset="age" constraint="number(.) > 10"
required="true()" type="xs:integer"/>

In addition, for implementations that support it, you can also use XML
Schema types, which are quite powerful.

All this is part of the beauty of XForms!

-Erik

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Orbeon Forms - Web Forms for the Enterprise Done the Right Way
http://www.orbeon.com/

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