From http://www.w3schools.com (Copyright Refsnes Data)

XForms Model

The XForms model defines a template for the data to be collected in a form.

The XForms Framework

The purpose of an HTML form is to collect data. XForms has the same purpose.

With XForms, input data is described in two different parts:

The XForm model (to describe the data and the logic)
The XForm user interface (to display and input the data)

The XForms model defines what the form is, what data it contains, and what it should do.

The XForms user interface defines the input fields and how they should be displayed.

The XForms Model

The XForms model is used to describe the data.

The data model is an instance (a template) of an XML document.

The XForms model defines a data model inside a <model> element:

<model>

<instance>
  <person>
    <fname/>
    <lname/>
  </person>
</instance>

<submission id="form1"
action="submit.asp"
method="get"/>

</model>

From the example above, you can see that the XForms model uses an <instance> element to define the XML template for data to be collected, and a <submission> element to describe how to submit the data.

The XForms model does not say anything about the visual part of the form (the user interface).

XForms Namespace

If you are missing the XForms namespace in these examples, or if you don't know what a namespace is, it will be introduced in the next chapter.

The <instance> Element

The XForms model uses an <instance> element to define the data to be collected.

XForms is always collecting data for an XML document. The <instance> element in the XForms model defines the XML document.

In the example above the "data instance" (the XML document) the form is collecting data for looks like this:

<person>
  <fname/>
  <lname/>
</person>

After collecting the data, the XML document might look like this:

<person>
  <fname>John</fname>
  <lname>Smith</lname>
</person>

The <submission> Element

The XForms model uses a <submission> element to describe how to submit the data.

The <submission> element defines a form and how it should be submitted. In the example above, the id="form1" attribute identifies the form, the action="submit.asp" attribute defines the URL to where the form should be submitted, and the method="get" attribute defines the method to use when submitting the data.

The XForms User Interface

The XForms user interface is used to display and input the data.

The user interface elements of XForms are called controls (or input controls):

<input ref="fname"><label>First Name</label></input>
<input ref="lname"><label>Last Name</label></input>
<submit submission="form1"><label>Submit</label></submit>

In the example above the two <input> elements define two input fields. The ref="fname" and ref="lname" attributes point to the <fname> and <lname> elements in the XForms model.

The <submit> element has a submission="form1" attribute which refers to the <submission> element in the XForms model. A submit element is usually displayed as a button.

Notice the <label> elements in the example. With XForms every input control element has a required <label> element.

You'll Need A Container

XForms is not designed to work alone. There is no such thing as an XForms document.

XForms has to run inside another XML document. It could run inside XHTML 1.0, and it will run inside XHTML 2.0.

All Together Now

If we put it all together the document will look like this:

<xforms>

<model>
<instance>
  <person>
    <fname/>
    <lname/>
  </person>
</instance>
<submission id="form1"
action="submit.asp"
method="get"/>
</model>

<input ref="fname"><label>First Name</label></input>
<input ref="lname"><label>Last Name</label></input>
<submit submission="form1"><label>Submit</label></submit>

</xforms>

And the page will display pretty much like this:

First Name
Last Name

The XForms Processor

An XForms Processor built into the browser will be responsible for submitting the XForms data to a target.

The data can be submitted as XML and could look something like this:

<person>
  <fname>Hege</fname>
  <lname>Refsnes</lname>
</person>

Or it can be submitted as text, looking something like this:

fname=Hege;lname=Refsnes