For the <xforms:output> control to display an image, you need to:

• Have a mediatype attribute on the <xforms:output>. That attribute must refer to an image mediatype, such as image/* or image/jpeg.

• Use the value attribute on <xforms:output> or bind to the control to a node without type, with an xs:anyURI type or with an xs:base64Binary type.

The resulting value from the instance is interpreted either as a URI pointing to an image, or as a base64-encoded binary representation of the image. The image will display in place of the xforms:output. It is possible to dynamically change the image pointed to. For example:

The image URI may or may no be reachable from the client browser. Orbeon Forms hides this from the developer. For example, to upload and show an image:

In that example, the upload control stores a temporary URI pointing to a local file: resource. While this URI is not visible from the client web browser, the output control automatically proxies it so that the end user can see the image.

When an xforms:output control has a mediatype attribute with value text/html, the value of the node to which the control is bound is interpreted as HTML content. Consider the following XForms instance:

You bind an xforms:output control to the html-content node as follows:

This will display the result as HTML, as expected: "This is in bold!". If the mediatype is not specified, the result would be instead: "This is in <b>bold</b>!". In the XForms instance, the HTML content must be escaped as text. On the other hand, the following content will not work as expected:

You often want to present a form without allowing the user to enter data. An easy solution is to use the readonly MIP in the model. By making for example the root element of an instance read-only, all the controls bound to any node of that instance will appear read-only (because the read-only property is inherited in an instance):

Sometimes, read-only controls don't appear very nicely in web browsers. For example, a combo box will appear grayed out. It maybe be hard to read, and there is not much point showing a combo box since the user can't interact with it. Furthermore, with some browsers, like IE 6 and earlier, it is not even possible to make disabled controls appear nicer with CSS. In order to make read-only versions of forms look nicer, Orbeon Forms supports a special extention attribute that allows you to produce a "static" appearance for read-only controls. You enable this on your first XForms model:

The attribute takes one of two vales: static or dynamic (the default). When using the value static, read-only controls do not produce disabled HTML form controls. This has one major limitation: you can't switch a control back to being read-write once it is displayed as read-only.

You can also set the xxforms:readonly-appearance attribute directly on individual XForms controls.

See the Government Forms sample application's View Read-Only option for an example of this feature in action.

It is usually recommended to use native XML types within XForms instances, as this guarantees interoperability and maintainability. For example, a date of January 10, 2005 is stored in ISO format as: 2005-10-01. However it is often necessary to format such values on screen in a user-readable format, like "January 10, 2005", "10 janvier 2005", or "10. Januar 2005".

Orbeon Forms provides an extension attribute, xxforms:format, for that purpose. xxforms:format must contain an XPath 2.0 expression. In your XPath expression you can use all the XPath 2.0 functions, including those for date manipulation (external documentation). However since XPath 2.0 functions don't provide any facility for date and time formatting, you can in this attribute also use the following XSLT 2.0 functions:

• format-date() (external documentation)

• format-dateTime() (external documentation)

• format-time() (external documentation)

• format-number() (external documentation)

The XPath expression is evaluated by the XForms engine whenever the value bound to the xforms:input control changes and needs to be updated on screen. It is evaluated in the context of the instance node bound to the control. This means that the current value of the control can be accessed with ".". Often the value must be converted (for example to a date) in which case the conversion can be done with a XPath 2.0 constructor such as xs:date(.) or with as cast such as (. cast as xs:date?).

When using xforms:input and a bound xs:date type, you can control the formatting of the date using the xxforms:format extension attribute on the xforms:input control. For example:

When using xforms:output, you can control the formatting of the date using the xxforms:format extension attribute on the xforms:output control.

For both xforms:input and xforms:output, if the bound node is of one of the following types: xs:date, xs:dateTime, xs:time, xs:decimal, xs:integer, xs:float, and xs:double, and if no xxforms:format attribute is present on the control, formatting is based on properties. If the properties are missing, a built-in default formatting is used. The default properties, as well as the built-in defaults, are as follows:

They produce results as follows:

• 2004-01-07 as xs:date is displayed as Wednesday January 7, 2004

• 2004-01-07T04:38:35.123 as xs:dateTime is displayed as Wednesday January 7, 2004 04:38:35 UTC

• 04:38:35.123 as xs:time is displayed as 04:38:35 UTC

• 123456.789 as xs:decimal is displayed as 123,456.79

• 123456.789 as xs:integer is displayed as 123,456

• 123456.789 as xs:float or xs:double is displayed as 123,456.789

Note:

• With the "if" condition in the XPath expressions, a value which cannot be converted to the appropriate type is simply displayed as is.
• For values of type xs:time or xs:dateTime, if you wish the time to be displayed using the current timezone instead of UTC, replace in the value attribute UTC by [ZN].

Orbeon Forms supports extensions events dispatched to an instance when it becomes valid or invalid: xxforms-valid and xxforms-invalid. These events are dispatched just before xforms-revalidate completes, to all instances of the model being revalidated. For a given instance, either xxforms-valid or xxforms-invalid is dispatched for a given revalidation.

These events can be used, for example, to toggle the appearance of icons indicating that a form is valid or invalid:

Orbeon Forms supports the built-in xxforms:xml extension type. This types checks that the value is well-formed XML:

Note that this checks the string value of the node, which means that the node must contain escaped XML.

When an XML Schema is provided, Orbeon Forms supports controlling whether a particular instance is validated in "lax" mode, "strict" mode, or not validated at all.

Orbeon Forms implements a "lax" validation mode by default, where only elements that have definitions in the imported schemas are validated. Other elements are not considered for validation. This is in line with XML Schema and XSLT 2.0 lax validation modes, and with the default validation mode as specified in XForms 1.1

In addition, the author can specify the validation mode directly on each instance with the extension xxforms:validation attribute, which takes values lax (the default), strict (the root element has to have a definition in the schema and must be valid), or skip (no validation at all for that instance).

Nodes validated through a schema receive datatype annotations, which means that if an element or attribute is validated against xs:date in a schema, an XForms control bound to that node will display a date picker.

When using XPath 2.0, the following functions from XSLT 2.0 are also available:

• format-date() (external documentation)

• format-dateTime() (external documentation)

• format-time() (external documentation)

• format-number() (external documentation)

The following functions are implemented:

• xxforms:if()

  This function implements the semantic of the XForms 1.0 if() function. See Note About XPath 2.0 Expressions for more details.

• xxforms:call-xpl($xplURL as xs:string, $inputNames as xs:string*, $inputElements as element()*, $outputNames as xs:string+) as document-node()*

  This function lets you call an XPL pipeline.

  1. The first argument, $XPLurl, is the URL of the pipeline. It must be an absolute URL.
  2. The second argument, $inputNames, is a sequence of strings, each one representing the name of an input of the pipeline that you want to connect.
  3. The third argument, $inputElements, is a sequence of elements to be used as input for the pipeline. The $inputNames and $inputElements sequences must have the same length. For each element in $inputElements, a document is created and connected to an input of the pipeline. Elements are matched to input name by position, for instance the element at position 3 of $inputElements is connected to the input with the name specified at position 3 in $inputNames.
  4. The fourth argument, $outputNames, is a sequence of output names to read.
  5. The function returns a sequence of document nodes corresponding the output of the pipeline. The returned sequence will have the same length as $outputNames and will correspond to the pipeline output with the name specified on $outputNames based on position.

  The example below shows a call to the xxforms:call-xpl function:

  xxforms:call-xpl ('oxf:/examples/sandbox/xpath/run-xpath.xpl', ('input', 'xpath'), (instance('instance')/input, instance('instance')/xpath), 'formatted-output')/*, 'html')

• xxforms:evaluate($xpath as xs:string) as item()*

  The xxforms:evaluate() function allows you to evaluate XPath expressions dynamically. For example:

  <xforms:input ref="xxforms:evaluate(concat('instance(''my-instance'')/document', my-xpath))"><xforms:label>...</xforms:label></xforms:input>

• xxforms:serialize($item as node(), $format as xs:string?) as xs:string

  The xxforms:serialize() function allows you to serialize an XML node to XML, HTML, XHTML or text. For example:

  <xforms:bind nodeset="my-html" calculate="xxforms:serialize(instance('my-instance'), 'html')"/>

• xxforms:context($element-id as xs:string) as node()

  The xxforms:context() function allows you to obtain the single-node binding for an enclosing xforms:group, xforms:repeat, or xforms:switch. It takes one mandatory string parameter containing the id of an enclosing grouping XForms control. For xforms:repeat, the context returned is the context of the current iteration.

  <xforms:group ref="employee" id="employee-group"><!-- The context is being set to another instance that controls the visibility of the group. --><xforms:group ref="instance('control-instance')/input"><!-- Using xxforms:context() allows reclaiming the context of the enclosing group. --><xforms:input ref="xxforms:context('employee-group')/name"><xforms:label>Employee Name</xforms:label></xforms:input></xforms:group></xforms:group>
  Note

  See also the XForms 1.1 context() function, which returns the current evaluation context:

  <xforms:group ref="employee"><xforms:setvalue ref="instance('foo')/name" value="context()/name"/></xforms:group>

• xxforms:bind(bind-id as xs:string) as node()*

  The xxforms:bind() function returns the node-set of a given <xforms:bind>:

  <!-- The following... --><xforms:input bind="my-bind">...</xforms:input><!-- ...is equivalent to this: --><xforms:input ref="xxforms:bind('my-bind')">...</xforms:input>

  xxforms:bind() is particularly useful when referring to a bind is subject to a condition:

  <xforms:hint ref="for $bind in xxforms:bind('my-hint') return if (normalize-space($bind) = '') then instance('default-hint') else $bind"/>

• xxforms:repeat-nodeset($repeat-id as xs:string) as node()*

  The xxforms:repeat-nodeset() function returns the node-set of an enclosing xforms:repeat. It takes one mandatory string parameter containing the id of an enclosing repeat XForms control.

  <xforms:repeat id="employee-repeat" nodeset="employee"><xhtml:div><xforms:output value="count(xxforms:repeat-nodeset('book-repeat'))"/></xhtml:div></xforms:repeat>

• xxforms:instance($instance-id as xs:string) as element()?

  The xxforms:instance() function works like the standard instance() function except that it searches for instances in all the models of the XForms document (the standard instance() function only searches within the current XForms model).

  <xforms:model id="main-model"><xforms:instance id="main-instance">...</xforms:instance></xforms:model><xforms:model id="resources-model"><xforms:instance id="resources-instance">...</xforms:instance></xforms:model>...<xforms:group model="main-model"><xforms:output value="xxforms:instance('resources-instance')/titles/company-information"/></xforms:group>

• xxforms:index($repeat-id as xs:string?) as xs:integer

  The xxforms:index() function behaves like the standard XForms index() function, except that its argument is optional. When the argument is omitted, the function returns the index of the closest enclosing <xforms:repeat> element. This function must always be used within <xforms:repeat> otherwise an error is raised.

  <xforms:repeat nodeset="employee" id="employee-repeat"><div><xforms:trigger><xforms:label>Add One</xforms:label><xforms:insert ev:event="DOMActivate" nodeset="../employee" at="xxforms:index()"/></xforms:trigger></div></xforms:repeat>

• xxforms:property($property-name as xs:string) as xs:string?

  The xxforms:property() function retrieves the value of a property defined in properties.xml. If no property exists with the given name, returns an empty sequence.

  <xforms:repeat nodeset="employee" id="employee-repeat"><div><xforms:trigger><xforms:label>Read Property</xforms:label><xforms:setvalue ev:event="DOMActivate" ref="my-property" value="xxforms:property('my.property.name')"