XForms

About me

Researcher at the Dutch national research centre CWI (first European Internet site)

Co-designed the programming language ABC, that was later used as the basis for Python

In the late 80's designed and built a browser, with extensible markup, stylesheets, vector graphics, client-side scripting, etc. Ran on Mac, Unix, Atari ST

Organised 2 workshops at the first Web conference in 1994

Co-author of HTML4, CSS, XHTML, XML Events, XForms, etc

Chair of W3C HTML and Forms working groups

Until recently Editor-in-Chief of ACM/interactions.

Problems with HTML Forms

Presentation oriented, mixing data and presentation
No types, Ping-ponging to the server
Reliance on scripting
Problems with non-Western characters
Accessibility problems
Hard to make cross-device for single authoring
Impoverished data-model, no integration with existing streams
Hard to manage, hard to see what is returned
No support for wizards and shopping carts etc.

Soundbite: "Javascript accounts for 90% of our headaches in complex forms, and is extremely brittle and unmaintainable."

The Essence: Separation of Values from Controls

There are two parts to the essence of XForms. The first is to separate what is being returned from how the values are filled in. Separation of values from controls

The model specifies the values being collected (the instance), and their related logic:
- Types, restrictions
- Initial values, Relations between values
The body of the document then binds forms controls to values in the instance

The Essence: Intent-based Controls

The second part is that the form controls, rather than expressing how they should look (radio buttons, menu, etc), express their intent (this control selects one value from a list).

You then use styling to say how they should be represented, possibly with different styling for different devices (as a menu on a small screen, as radio buttons on a large screen).

Colour: red green blue

XForms improves the user experience

XForms has been designed to allow much to be checked by the browser, such as

types of fields being filled in
that a particular field is required
or that one date is later than another.

This reduces the need for round trips to the server or for extensive script-based solutions, and improves the user experience by giving immediate feedback on what is being filled in.

It is easier to author and maintain complicated forms

Because XForms uses declarative markup to declare properties of values, and to build relationships between values, it is much easier for the author to create complicated, adaptive forms, and doesn't rely on scripting.

An HTML Form converted to XForms looks pretty much the same, but when you start to build forms that HTML wasn't designed for, XForms becomes much simpler.

It is XML, and it can submit XML

XForms is properly integrated into XML: it is in XML, the data it collects in the form is XML, it can load external XML documents as initial data, and can submit the results as XML.

By including the user in the XML pipeline, it at last means you can have end-to-end XML, right up to the user's desktop.

However, it still supports 'legacy' servers.

XForms is also a part of XHTML2.

It combines existing XML technologies

Rather than reinventing the wheel, XForms uses a number of existing XML technologies, such as

XPath for addressing and calculating values
XML Schema for defining data types.

This has a dual benefit:

ease of learning for people who already know these technologies
the ability for implementors to use off-the-shelf components to build their systems.

It integrates into existing data streams

Data can be pre-loaded into a form from external sources.

Existing Schemas can be used.

It integrates with SOAP and XML RPC.

Doesn't require new server infrastructure.

It is device independent

Thanks to the intent-based controls, the same form can be delivered without change to a traditional browser, a PDA, a mobile phone, a voice browser, and even some more exotic emerging clients such as an Instant Messenger.

This greatly eases providing forms to a wide audience, since forms only need to be authored once.

It is rather easy to implement

XMLDOMCSSJavascriptXHTMLXPathXForms

=Regular XHTML Browser

Time to build all of above: 3 programmers, 4 months

Total footprint (on IPAQ implementation): 400K (above Java VM)

In fact this is quite evolutionary: XForms uses existing W3C components. It is only the XForms processing model that describes when to calculate values that is really new.

It is royalty-free and unencumbered

Open standard

Wide industry support

Widely implemented

No vendor lock-in!

(If you think this is a good idea, join W3C!)

New Use Cases

Regular forms uses

Editing XML

Spreadsheets

Applications

As output transformation

Basic structure of XForms

Take this simple HTML form:

<html>
<head><title>Search</title></head>
<body>
    <form action="http://example.com/search" method="get">
         Find <input type="text" name="q">
         <input type="submit" value="Go">
    </form>
</body>
</html>

The main difference in XForms is that details of the values collected and how to submit them are gathered in the head, in an element called model; only the form controls are put in the body.

... basic structure

So in this case you put the following in the head (XForms elements and attributes are in lower case):

<model>
   <instance>
       <data xmlns=""><q/></data>
   </instance>
   <submission
       action="http://example.com/search"
       method="get"
       id="s"/>
</model>

The <form> element is now no longer needed; the controls in the body look like this:

<input ref="q"><label>Find</label></input>
<submit submission="s">
    <label>Go</label>
</submit>

Complete XForms search example

<html http://www.w3.org/2002/06/xhtml2/" xml:lang="en">
<head>
    <title>Search</title>
    <model>
        <instance>
            <data xmlns=""><q/></data>
        </instance>
        <submission
            action="http://example.com/search"
            method="get" id="s"/>
    </model>
</head>
<body>
  <p>
     <input ref="q"><label>Find</label></input>
     <submit submission="s"><label>Go</label></submit>
  </p>
</body>
</html>

Making the Submitted Values Explicit

Although in simple cases the instance element is optional, it is good practice to include an explicit instance, like this:

<instance>
        <data xmlns=""><q/></data>
</instance>
...
<input ref="q">
   <label>Search</label>
</input>

You immediately see that the only data value submitted is called "q".
The system will now also check that when you say ref="q" that there really is a q in the instance.
We've used <data> here, but you can use any tag you like.

Initial Values

For initialising controls including initialising checked boxes, and selected menu items etc., you just supply an instance with pre-filled values. For the search example:

<instance>
    <data xmlns=""><q>Keywords</q></data>
</instance>

would pre-fill the text control with the word Keywords.

Hidden Values

Any values in the instance that haven't been bound to by a control are by definition not visible to the user.
Therefore there is no need for hidden controls
To add a hidden value results to the search form, we change the instance to:

<instance>
    <data xmlns="">
        <q/>
        <results>10</results>
    </data>
</instance>

Getting Initial Values From Elsewhere

You don't have to specify the initial instance in the document itself, because you can load it from an external resource, like this:
```
<instance
  src="http://example.org/templates/t21.xml"/>
```

The resource then contains your data, like

<data>
   <w>640</w>
   <h>480</h>
   <d>8</d>
</data>

You can use a local file, like src="file:data.xml"

Configuring Hardware

This makes configuring hardware even easier than it now is: instead of the device hosting a web server that can deal with HTML Forms, all it has to do is deliver its configuration parameters as an XML document, and XForms provides the interface.

'Editing' any XML document

External instances give you immense power
The ref attribute on controls can be any XPath expression
XPath lets you select any element or attribute in an XML document
You can bring in any XML document as instance, even an XHTML document

... example

For instance to bind to the <title> element in an XHTML document
```
<input ref="/h:html/h:head/h:title">...
```
(i.e. the title element within the head element within the html element, all in the XHTML namespace)
or the class attribute on the body element:
```
<input ref="/h:html/h:body/@class">...
```

Editing example

Suppose a shop has very unpredictable opening hours (perhaps it depends on the weather), and they want to have a Web page that people can go to to see if it is open. Suppose the page in question has a single paragraph in the body:

<p>The shop is <strong>closed</strong> today.</p>

Well, rather than teaching the shop staff how to write HTML to update this, we can make a simple form to edit the page instead:

Editing XHTML page

<model>
   <instance
      src="http://www.example.com/shop.xhtml"/>
   <submission
      action="http://www.example.com/shop.xhtml"
      method="put" id="change"/>
</model>
...
<select1 ref="/h:html/h:body/h:p/h:strong">
<label>The shop is now:</label>
<item><label>Open</label><value>open</value></item>
<item><label>Closed</label><value>closed</value></item>
</select1>
<submit submission="change"><label>OK</label></submit>

The page must be correct XHTML (not HTML)
The server must accept the "put" method (or you can save the result to a file if it is on the local machine)
(It is examples like this that make the advantages of XHTML over HTML visible)

XForms controls

XForms has equivalent controls for everything that you can do in HTML.

But there is an important difference: XForms controls are not presentation based, but intent-based – they say what they are meant to achieve not how they do it.

... controls

For instance, a select control

<select1 ref="country">
  <label>Country</label>
  <item><label>Netherlands</label><value>nl</value></item>
  <item><label>United Kingdom</label><value>uk</value></item>
  <item><label>France</label><value>fr</value></item>
</select>

can be represented using radio buttons, a drop-down menu, a select list (or anything else suitable you can think of)

depending on the style-sheet or the choice of the device.

Country Netherlands United Kingdom France

XForms equivalents for simple HTML Forms features

As already said, XForms has equivalents for all HTML controls, such as text, text boxes, selecting one or many, file upload, etc.

A user agent may adapt an input control based on knowledge of the data-type involved.

For instance

<input ref="depart">
   <label>Departure date</label>
</input>

can pop up a date picker control.

Extra control: range

XForms has a couple of extra controls:

<range ref="volume"
       start="1" end="10" step="0.5">

may be represented with a slider or similar.

Extra control: output

The output control allows you to include values as text in the document.

Your current total is: <output ref="sum"/>

<output ref="sum"><label>Total</label></output>

This can be used to allow the user to preview values being submitted.

... output

You can also calculate values:

Total volume:
  <output value="height * width * depth"/>

(where height, width and depth are values collected by other controls.)

Wizards: toggle and switch

These are used to reveal and hide parts of the interface.

<switch>
   <case id="inputname">
      <input ref="name">...</input>
      <trigger>
         <label>Next</label>
         <toggle case="inputage"
                 ev:event="DOMActivate" />
      </trigger>
   </case>
   <case id="inputage">
      <input ref="age">...</input>
      <trigger>...</trigger>
   </case>
   ...
</switch>

An example

Repeat

Repeat allows you to bind to repeating items in an instance. There are also facilities to delete and insert items in a repeating set.

<expenses>
   <item>
      <date/><who/><what/><amount/><currency/>
   </item>
   <item>
      <date/><who/><what/><amount/><currency/>
   </item>
</expenses>

<repeat ref="expenses/item">
   <input ref="date"><label>Date</label></input>
   ...
</repeat>

You have already seen an example

Controlling Controls

In HTML you can specify that controls are disabled, or read-only but the only way you can change the property is with scripting.
XForms offers easy ways to control these properties, but has other properties you can specify as well

Properties

The 'model binding' properties that you can control are:

that a value is only relevant in certain circumstances (for instance name of spouse only if married)
that a value is readonly in certain circumstances
that a value is required (that a value must be supplied before the form can be submitted)
that a value has a constraint (for instance that the year of birth is earlier than the year of death)
that the value must conform to a type (for instance that it must be an integer), or
that it is calculated from other values (for instance that the total is the sum of some other values).

... properties

Note that in XForms it is the collected value that has the property, not the control, but the property shows up on all controls bound to the value.

These properties use a <bind> element that goes in the <model>. To use bind, you must have an explicit <instance> element.

Disabled Controls = relevant

To disable controls you use the relevant property. For instance, to say that the credit card number only needs to be filled in if the person is paying by credit, you can write:

<model>
   <instance><data xmlns="">
      <amount/><method/>
      <cc>
        <number/><expires/>
      </cc>
   </data></instance>
   <bind nodeset="cc"
      relevant="../method='credit'"/>
</model>

An example of what we are going to do

... relevant

<bind nodeset="cc"
      relevant="../method='credit'"/>

This states that the values within cc are only relevant when method has the value credit, and will therefore be disabled for other values of method.
A browser is free to decide how disabled controls are presented (and it may also allow you to specify in a stylesheet how they should look), but typically they will be grayed out in the normal way.

... writing the controls

The controls could be written like this (but note that there is no indication that they may get disabled: that is inherited from the value they refer to):

<select1 ref="method">
   <label>Method of payment:</label>
   <item>
      <label>Cash</label><value>cash</value>
   </item>
   <item>
      <label>Credit card</label><value>credit</value>
   </item>
</select1>
<input ref="cc/number"><label>Card number:</label></input>
<input ref="cc/expires"><label>Expiry date:</label></input>

Readonly Controls

Similarly to relevant, you can specify a condition under which a value is read-only. For instance:

<model>
   <instance><data xmlns="">
      <variant>basic</variant>
      <color>black</color>
   </data></instance>
   <bind nodeset="color"
         readonly="../variant='basic'"/>
</model>

This example says that the default value of color is black, and can't be changed if variant has the value basic.

Required Controls

A useful new feature in XForms is the ability to state that a value must be supplied before the form is submitted.

The simplest case is just to say that a value is always required. For instance, with the search example:

<model>
   <instance><data xmlns=""><q/></data></instance>
   <bind nodeset="q" required="true()"/>
   <submission .../>
</model>

... required

but like the readonly and relevant attributes, you can use any XPath expression to make a value conditionally required:

<bind nodeset="state"
      required="../country='USA'"/>

which says that the value for state is required when the value for country is "USA".

It is up to the browser to decide how to tell you that a value is required, but it may also allow you to define it in a stylesheet.

Constraint Property

This property allows you to add extra constraints to a value. For instance:

<bind nodeset="year" constraint=". &gt; 1970"/>

constrains the year to be after 1970.

Note the XPath use of "." to mean "this value".

Calculate Property

It is possible to indicate that a value in the instance is calculated from other values. For instance:

<bind ref="volume"
   calculate="../height * ../width * ../depth"/>

When a value is calculated like this, it automatically becomes readonly.

... calculate functions

There are a number of functions available, including:

arithmetic: + - * div mod
string manipulation: concat, substring, ...
date handling: days-from-date, seconds-from-dateTime, months, seconds, now
booleans: <= < >= > = != and or

conditionals using 'if':

<bind nodeset="taxrate"
  calculate="if(../salary &gt; 50000, 50, 33)"/>

Types

Any value can be given a type. The browser can then check that the values match the required type.
For instance, if the search example is actually only for searching for numbers (for instance for searching in a bug database), then we only have to add:
```
<bind nodeset="q" type="xsd:integer"/>
```
This will prevent the value being submitted unless it is an integer.
You can also apply a schema to a whole instance

... types

If you want to collect the URL of someone's homepage, then you can specify
```
<bind nodeset="homepage" type="xsd:anyURI"/>
```
As already mentioned, user agents can do special things when they know the data type of a value. For instance, pop up a date picker rather than require you to type in the characters of a date.

... types

There are a number of useful built-in types you can use, including:

xsd:string, xsd:normalizedString (a string with whitespace characters replaced by the space character).
xsd:integer, xsd:nonPositiveInteger, xsd:negativeInteger, xsd:nonNegativeInteger, xsd:positiveInteger
xsd:boolean
xsd:decimal, xsd:double
xsd:date, xsd:time, xsd:dateTime
xsd:anyURI (A URI)
xforms:listItems (A space-separated list of strings for use with select)
xforms:listItem (A string without any spaces)

... types

You can apply Schemas to instances:

<model schema="types.xsd">
...
</model>

or include them inline:

<model>
   ...
   <xsd:schema>
      ...
   </xsd:schema>
   ...
</model>

Combining Properties

If you have several binds referring to the same value, you can combine them:

<bind nodeset="q" type="xsd:integer"
                 required="true()"/>

Multiple Submissions

HTML only allows you to submit the data to one server, in a single way.
XForms allows you to submit the data to different servers, or in different ways.
For instance, the search example could allow the user to submit the search string to different search engines:

<model>
   <instance><data xmlns=""><q/></data></instance>
   <submission id="com"
       action="http://example.com/search"
       method="get"/>
   <submission id="org"
       action="http://example.org/search"
       method="get"/>
</model>

... multiple submissions

and then in the body:

<input ref="q"><label>Find:</label></input>
<submit submission="org">
    <label>Search example.org</label>
</submit>
<submit submission="com">
    <label>Search example.com</label>
</submit>

Find:

Submission Methods

Just as with HTML there are a number of ways to submit the data.
There is still support for GET, URL-encoded POST, and multipart formdata POST.
There are some new ways of submission; the most interesting are:method="post": posts the results as XMLmethod="put": puts the results as XML.
You can submit to a SOAP or XML RPC server as well as traditional ones.

... submission to file

An interesting use of this is something like:
```
<submission 
    action="file:results.xml"
    method="put"/>
```
which saves your results to the local filestore by using the file: scheme.
For a large form, you could have separate 'save to disk' and 'submit' buttons.

Life after Submit

The default when values have been submitted is for the result returned by the server to replace the whole document, just as with HTML.
There are other options, specified with the attribute replace on the submission element.
replace="instance" replaces only the instance
replace="none" leaves the form document as-is without replacing it.

... example of different submissions

For example, for an address-change form for a bank, you can provide two buttons
- prefill the form with name and address based on the account number
- submit the changed results
The first button replaces the instance with a new instance containing the details of the person with the account number, which you can then change;
the 'submit' button will then send the changed instance back, leaving the form as-is in the browser to allow further changes or to input a new account number to prefill.

... example

<model>
    <instance><data xmlns="">
        <accountnumber/><name/><address/>
    </data></instance>
    <submission method="get"
        action="http://example.com/prefill"
        id="prefill" replace="instance"/>
    <submission method="put"
        action="http://example.com/change"
        id="change" replace="none"/>
</model>
...
<input ref="accountnumber"><label>Account Number</label></input>
<submit submission="prefill"><label>Find</label></submit>
<input ref="name"><label>Name</label></input>
<textarea ref="address"><label>Address</label></textarea>
<submit submission="change"><label>Submit</label></submit>

More than one instance in a model

You can have more than one instance in a model.
You identify which one you want with an id attribute and the use of the instance() function.
If you don't identify which, then the first instance in the model is used
Particularly useful for inputting values from several external sources

... more than one instance

<model>
   <instance id="currencies">
      <currencies>
         <currency name="USD">125</currency>
         ...
   </instance>
   <instance id="costs">
      <item>
         <date/><amount/><currency/>
         ...
      </item>
   </instance>
</model>
...
<input ref="instance('costs')/date">
   <label>Date</date>
</input>

... more than one instance

<model>
   <instance>
      <employee xmlns="">
         <name/>
         <number/>
         <salary/>
         <taxrate/>
         ...
      </employee>
   </instance>
   <instance id="tax" src="/finance/taxes"/>

  <bind nodeset="taxrate"
    calculate="if(../salary &gt; instance('tax')/limit,
                  instance('tax')/highrate,
                  instance('tax')/lowrate)"/>

Using more than one instance

Useful for filling itemsets in select and select1:

<select ref="value">
   <label>...</label>
   <itemset nodeset="instance(x)">
      <label ref="names"/>
      <copy ref="values"/>
   </itemset>
</select>

or creating dynamic labels (think multilingual) [example]:

<label ref="instance(labels)/label[msg='age']"/>

<label> can also take src="..."

Implementations

At release XForms had more implementations announced than any other W3C spec had ever had at that stage

Different types of implementation:

plugin
native
'zero install'
proxy
editors
office suites

Many big players doing implementations, e.g.

Novell
Oracle
IBM
Sun (on Openoffice/Staroffice)
Mozilla
(More that are still secret)

Users

As you would expect with a new technology, first adopters are within companies and vertical industries that have control over the software environment used.

the entire British Insurance industry,
the US Navy (in submarines),
NASA (Jet Propulsion Laboratories),
UK Government (Planning Inspectorate),
Verifone - a payment company, for configuring petrol pumps,
Xerox, for an Enterprise Content Management system, to implement dynamic forms and to do XML binding to editing and adding for Wikis, Blogs, and content management, and another use in active development.
Yahoo for several internal applications.
NACS - the National Association of Consumer Stores for configuring and accessing data from a range of devices,
Vancity - A Canadian Credit Union, with public XForms-driven pages,
Daiwa - a Japanese Bank, for a transaction system,
German Shipbuilders, for configuring ships,
Fraunhofer (known for MP3) for configuring websites,
Bristol-Myers-Squibb (pharmaceutical),
Remia - a major Dutch food manufacturer,
KDDI: embedded in a Japanese mobile phone,
CDC: for disease control after hurricane Katrina

... users

That list is there just to give a taste, but amongst others not mentioned there are at least 3 fortune 500 companies who don't want it to be public knowledge so that their competitors don't get wind of it.

As more industries adopt XForms, the expectation is that it will then spread out into horizontal use.

XForms for Web Applications

XForms has everything needed for an application:

A data model
Processing
Input
Output

People are already using XForms for some pretty exciting applications. xport.net who produce FormsPlayer are doing the most interesting stuff, by using SVG as the stylesheet language. They have produced examples such as a world clock, a contacts database, and even Google Maps in XForms!

world clock in XForms

maps

The interesting thing about this last example is that it is 25K of XForms, compared with 200K+ of javascript...

This is largely thanks to the declarative programming model of XForms, that means that you don't have to deal with lots of the fiddly administrative details.

Bear in mind that empirical evidence suggests that a program that is an order of magnitude larger takes 34 times as much effort; or put the other way, a program that is an order of magnitude smaller costs 3% of the effort...

Conclusion (XForms)

XForms is achieving critical mass much faster than we had anticipated. Companies large and small, consortia, even governments and government agencies are beating a path to our door.

Apart from offering a far more managable base for forms on the web, we believe that XForms is an excellent basis for future web applications, because it offers a model that gives you:

Accessible applications
Device-independent applications
Much less programming.

More Information

XForms home page: www.w3.org/MarkUp/Forms, and if your company is a member: www.w3.org/MarkUp/Forms/Group
XForms: www.w3.org/TR/xforms
XPath: www.w3.org/TR/xpath

Steven Pemberton: www.cwi.nl/~steven

These slides: well, find 'em!

XForms

About me

HTML Forms: a great success!

Searching

Buying

Logging in

Configuring hardware

Reading mail

Composing email

Etc etc

So why XForms?

Problems with HTML Forms

XForms, the Approach and the Advantages

The Essence: Separation of Values from Controls

The Essence: Intent-based Controls

Overview of Advantages

XForms improves the user experience

It is easier to author and maintain complicated forms

It is XML, and it can submit XML

It combines existing XML technologies

It integrates into existing data streams

It is device independent

It is internationalized

It is accessible

It is rather easy to implement

It is royalty-free and unencumbered

New Use Cases

Basic structure of XForms

... basic structure

Complete XForms search example

Making the Submitted Values Explicit

Initial Values

Hidden Values

Getting Initial Values From Elsewhere

Configuring Hardware

'Editing' any XML document

... example

Editing example

Editing XHTML page

XForms controls

... controls

XForms equivalents for simple HTML Forms features

Extra control: range

Extra control: output

... output

Wizards: toggle and switch

Repeat

Controlling Controls

Properties

... properties

Disabled Controls = relevant

... relevant

... writing the controls

Readonly Controls

Required Controls

... required

Constraint Property

Calculate Property

... calculate functions

Types

... types

... types

... types

Combining Properties

Submitting

Multiple Submissions

... multiple submissions

Submission Methods

... submission to file

Life after Submit

... example of different submissions

... example

More than one form in a document

... more than one form

More than one instance in a model

... more than one instance

... more than one instance

Using more than one instance

Implementations

Users