XForms Unplugged (original) (raw)

About the Speaker

Steven Pemberton is a researcher at the CWI, The Centre for Mathematics and Computer Science, a nationally-funded research centre in Amsterdam, The Netherlands, the first non-military Internet site in Europe.

Steven's research is in interaction, and how the underlying software architecture can support the user. At the end of the 80's he built a style-sheet based hypertext system called Views.

Steven has been involved with the World Wide Web since the beginning. He organised two workshops at the first World Wide Web Conference in 1994, chaired the first W3C Style Sheets workshop, and the first W3C Internationalisation workshop. He was a member of the CSS Working Group from its start, and is a long-time member (now chair) of the HTML Working Group, and co-chair of the XForms Working Group. He is co-author of (amongst other things) HTML 4, CSS, XHTML and XForms.

Steven is also Editor-in-Chief of ACM/interactions.

Overview

HTML Forms, introduced in 1993, were the basis of the e-commerce revolution. After 10 years experience, it has become clear how to improve on them, for the end user, the author, and the owners of the services that the forms are addressing. XForms is a new technology, announced in October 2003, intended to replace HTML Forms.

The advantages of XForms include:

• It 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, 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 to what is being filled in.
• It is XML, and it can submit XML.
• 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, and XML Schemas for defining data types. This has a dual benefit: ease of learning for people who already know these technologies, and implementors can use off-the-shelf components to build their systems.
• It is internationalized.
• It is accessible: XForms has been designed so that it will work equally well with accessible technologies (for instance for blind users) and with traditional visual browsers.
• It is device independent: 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 easier to author complicated forms.

The presenter is one of the authors of the XForms specifications, and is chair of the Forms Working Group that produced the technology.

HTML Forms: a great success!

• Forms have been the basis of the e-commerce revolution
• You find them everywhere on the web

Searching

Buying

Logging in

Configuring hardware

Reading mail

Composing email

Etc etc

• Tracking packages
• calculating currencies
• submitting taxes
• banking
• expenses
• calendars
• blogging
• wiki
• ...

So why XForms?

After a decade of experience with HTML Forms, we now know more about what we need and how to achieve it

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."

XForms, the Approach and the Advantages

XForms has been designed based on an analysis of HTML Forms, what they can do, and what they can't.

The Approach

The essence is to separate what is being returned from how the values are filled in.

• The model specifies the values being collected (theinstance), 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

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 internationalized

Thanks to using XML, there are no problems with loading and submitting non-Western data.

It is accessible

XForms has been designed so that it will work equally well with accessible technologies (for instance for blind users) and with traditional visual browsers.

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:

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 calledmodel; only the form controls are put in the body.

... basic structure

So in this case the minimum you need in the head is (XForms elements and attributes are in lower case):

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

Find Go

Complete XForms search example

<h:html xmlns:h="http://www.w3.org/1999/xhtml" xmlns="" title="undefined" rel="noopener noreferrer">http://www.w3.org/2002/xforms"> <h:head> <h:title>Search <submission** **action="http://example.com/search"** **method="get" id="s"/> <h:body> <h:p> Find Go

Making the Submitted Values Explicit

It is good practice to include an explicit instance, like this:

... explicit values

• 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 the tag <data> here, but you can choose 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:

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

• 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:

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="" title="undefined" rel="noopener noreferrer">http://example.org/templates/t21.xml"**/>
• The resource then contains your data, like 640 480 8
• You can use a local file, likesrc=" file:data.xml"

'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
  ...
  (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:
  ...

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:

The shop is closed today.

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

• The page must be correct XHTML (not HTML)
• The server must accept the "put" method

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

can be represented using

• radio buttons
• a select list
• a drop-down menu
• (or anything else suitable you can think of)

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

XForms equivalents for simple HTML Forms features

XForms has equivalents for all of 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

can pop up a date picker control.

Extra control: range

XForms has a couple of extra controls:

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:

or

Total

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

... output

You can also calculate values:

Total volume:

(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.

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.

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:

... relevant

• 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"**> Method of payment: Cashcash Credit cardcredit

Readonly Controls

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

This example says that the default value of color isblack, 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:

... 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=". > 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 becomesreadonly.

... 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':
  

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 withselect)
• xforms:listItem (A string without any spaces)

... types

You can apply Schemas to instances:

or include them inline:

Combining Properties

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

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

Submitting

Now to look at details of submission, like multiple submissions, submission methods, and what happens after submission.

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:

... multiple submissions

and then in the body:

Find: <submit **submission="org"**> Search example.org <submit **submission="com"**> Search example.com

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 XML method="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:
  
  which saves your results to the local filestore by using thefile: 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 attributereplace 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 instance, 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

More than one form in a document

• For more than one form in a document, you can use one model per form, but then you need to identify which form each control refers to
• You do this with an id attribute on each model, and amodel attribute on each control:

... more than one form

<model **id="search"**> <submission id="s" .../> <model **id="login"**> <submission id="l" .../> ... <input **model="search"** ref="q">Find Go ... <input **model="login"** ref="user">User name <secret **model="login"** ref="passwd">Password Log in

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

... more than one instance

Using more than one instance

Useful for filling itemsets in select and select1:

or creating dynamic labels (think multilingual):

can also take src="..."

Conclusion

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.

• 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
• Many big players doing implementations, e.g.: Novell, Oracle, IBM, Sun
• Also several excellent implementations from newcomers, eg FormsPlayer

"The age of the fat client is past" -- an implementor

More Information

• The origin: www.w3.org/Markup/Forms, and if your company is a member: [www.w3.org/Markup/Forms/Group](http:// www.w3.org/Markup/Forms/Group/)
• XForms: http://www.w3.org/TR/xforms
• XPath: http://www.w3.org/TR/xpath
• Steven Pemberton: www.cwi.nl/~steven
• Seybold information: seybold365.com
• Feedback, comments and suggestions on the session and event:
  Seybold Director of Content, Cynthia Wood, Cynthia.Wood@mlii.com
  Seybold VP & General Manager, James Smith, James.Smith@mlii.com