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RE: validating an xform

From: Clark, John <CLARKJ2@ccf.org>
Date: Tue, 25 Nov 2008 09:39:34 -0500
Message-ID: <F122C25B4CD6F34BB119A9759367960104595C4B@CCHSCLEXMB59.cc.ad.cchs.net>
To: xforms <www-forms@w3.org>
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"
    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@w3.org 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!


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Received on Tuesday, 25 November 2008 14:40:31 UTC

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