XForms - Current developments

Steven Pemberton, CWI, Amsterdam

Differences

This is from one of the appendices of the XForms 2 spec.

• Expressions
  • Uses XPath n, instead of XPath 1; allows amongst other things atomic values and typed values
  • Attribute Value Templates (AVTs) allow calculated values to be used in attributes, enabling the deprecation of many child elements
  • Custom functions and variables have been added
  • New functions: valid() relevant() readonly() required() case() serialize() seconds-from-epoch() bind() element() attribute() parse() eval() eval-in-context() location-uri() location-param() uri-scheme() uri-scheme-specific-part() uri-authority() uri-user-info() uri-host() uri-port() uri-path() uri-query() uri-fragment() uri-param-names() uri-param-values()
• Data
  • External instance fallback: if @src on <instance/> fails, the instance is initialised with the inline content.
  • Multiple MIPs of the same property allowed on one node.
  • New whitespace MIP defines how space is treated in values
  • json, csv and other external instance data formats are supported
  • slight change in how nested binds select items.
• Types
  • The definition of validity has been slightly changed to allow empty non-required values to be considered valid. Consequently, the XForms datatypes no longer all include empty as a possible value.
  • better email type
  • new types:
    • two IRI types
    • iemail type
    • telephone number type
    • HTMLFragment type
• Controls
  • The @nodeset attribute is deprecated in favour of @ref everywhere
  • a new dialog element
  • a new <control/> element for embedding an XForm in an XForm, plus actions <return/>, and <renew/>
  • repeat has an @indexref attribute
  • <repeat appearance='minimal' .../> <group appearance='minimal' ...>
  • switch has a @caseref attribute
  • an item of a select1 can be deselected
  • label, hint, help, alert
    • attributes have been added as alternatives to the child elements
    • properties have been added to the bind element
    • label elements/attributes are consequently now optional on controls
    • Unification of how output, label, help, hint, and alert work.
    • No linking on <help/>
    • @appearance on <alert> (erratum)
• Actions
  • @iterate has been added to actions
  • <update/>
  • <cancel/> action added
  • <insert/> no longer makes values of type ID unique
  • <insert/> and <delete/> indexes must be in range.
  • All actions that have an IDREF attribute now dispatch an xforms-action-error if that attribute does not identify a (suitable) element.
  • ability to call script (such as JavaScript) from actions, including passing parameters
  • <reset instance="id"/> and <retain/>
  • <return/>, and <renew/> to go with <control/> element.
  • Small change in the order of evaluation of <load/> attributes
• Events
  • add properties to dispatched events
  • xforms-action-warning event added
  • xforms-submit-ready event added
  • xforms-rebuild, xforms-revalculate, xforms-revalidate, xforms-refresh, and xforms-reset events deprecated in favour of the respective actions
  • xforms-submit-serialize deprecated
  • event handlers are no longer disabled when their associated controls are disabled.
  • events now conditionally cancellable with <cancel/> action
• Submission
  • @response-mediatype overrides incoming mediatype
  • get is default submission method
  • @nonrelevant replaces @relevant, with new options
  • @value available for providing data to be submitted
• Other
  • <form> element as root element if one is needed
  • p3ptype has been deprecated

Differences

Lots of small changes, like new types, new functions.

Doesn't specify which version of XPath is used any more, but must be > 1

AVTs

These have been present in processors for a long time.

<output class="{xpath expr}" ref="..."/>

Label (etc) attributes

@label @alert @hint @help as alternatives

<input ref="h" label="height" alert="Must be positive"/>

Fallback on instance

<instance src="saved.xml">
   <game xmlns="">
      <score>0</score>
   </game>
</instance>

You can already do this, with submissions and events, but it's much more work.

Event

New event: xforms-refresh-done

Similar to xforms-ready: Tells you when the processor is idle. Good for generation-based programs, such as Game of Life.

whitespace property

<bind ref="email" whitespace="trim"/>
<bind ref="cc" whitespace="remove"/>
<bind ref="name" whitespace="collapse"/>

• preserve: all whitespace is preserved (default)
• remove: all whitespace is removed,
• trim: all whitespace from the beginning and end of the string is removed,
• collapse: each occurrence of multiple whitespace is replaced with a single space character
• normalize: a combination of 'trim' and 'collapse'.

reset and retain instances

It's now possible to preserve the state of an instance, and restore it later.

<form> element

XForms has never had a root element, since it was always designed to be embedded in other languages.

Now it has one, for stand-alone processors.

<control/>

Embeds an XForm in another, with communication

<control label="before" resource="histogram.xf" ref="before"/>
<control label="after" resource="histogram.xf" ref="after"/>

Acts just like a regular control, with label, alert, etc.

@ref data is shared between the two, if one changes the data, the other sees the change.

In the embedded control

<shared ref="data" initial="external"/>

specifies the shared content, and where the initial values come from.

Events can be sent between the two.

If a form is not embedded, it performs normally.