Multilingual XForms

Steven Pemberton, CWI, Amsterdam

Contents

Technique

Everywhere you have a <label> element with text, you can replace it with a <label> with a ref attribute, or using an output. Instead of:

<label>How can you help?</label>

you put the text in an instance:

<instance id="m">
  <messages xmlns="" lang="en">
    ...
    <help>How can you help?</help>
    ...
  </messages>
</instance>

and use an output in the label:

<label><output ref="instance('m')/help"/></label>

or a ref:

<label ref="instance('m')/help"/>

Translate

Then you translate the messages instance into as many languages as you like, and store each in a file.

To switch language, you use a submission to replace the messages instance with one from one of the files:

<submission replace="instance" instance="m" resource="french.xml" 
            method="get" serialization="none"/>

The serialization="none" is so that no data from the default instance gets sent with the submission

method="get" is the default, so is not strictly needed.

An Example

Say you have an XForm that starts like this:

Please help us discover problems and solutions that would improve our processes.

<select1 ref="choice" appearance="full">
   <label>How can you help?</label>
   <item><label>You know a problem that needs to be fixed</label>
         <value>problem</value></item>
   <item><label>You know a 'solution' that doesn't work</label>
         <value>failure</value></item>
   <item><label>You have a prediction about a future possible failure</label>
         <value>prediction</value></item>
</select1>

Which looks like this:

Source

Prepare

You create an instance to contain your current messages:

<instance id="m">
  <messages xmlns="" lang="en">
    <intro>Please help us discover problems and solutions to improve our processes.</intro>
    ...
  </messages>
</instance>

Now you can change the first line to this:

<output ref="instance('m')/intro"/>

<select1 ref="choice" appearance="full">
   <label>How can you help?</label>
   <item><label>You know a problem that needs to be fixed</label>
         <value>problem</value></item>
   <item><label>You know a 'solution' that doesn't work</label>
         <value>failure</value></item>
   <item><label>You have a prediction about a future possible failure</label>
         <value>prediction</value></item>
</select1>

Itemset

For the select1, we add a number of messages to the message instance, one for the label, and one each for the items, along with the value that it matches:

<instance id="m">
   <messages xmlns="" lang="en">
      <intro>Please help us discover problems and solutions to improve our processes.</intro>
      <choice>
         <label>How can you help?</label>
         <item value="problem">You know a problem that needs to be fixed</item>
         <item value="failure">You know a 'solution' that doesn't work</item>
         <item value="prediction">You have a prediction about a future possible failure</item>
      </choice>
   </messages>
</instance>

Now you can use a ref for the label, and an itemset to replace the items in the select1:

<select1 ref="choice">
   <label ref="instance('m')/choice/label"/>
   <itemset ref="instance('m')/choice/item">
      <label ref="."/>
      <value ref="@value"/>
   </itemset>
</select1>

Translate

Then you translate the messages instance into as many languages as you wish, store them in files, and record the languages you have used:

<languages>
  <language file="messages-ca.xml">Català</language>
  <language file="messages-de.xml">Deutsch</language>
  <language file="messages-en.xml">English</language>
  <language file="messages-es.xml">Español</language>
  <language file="messages-fr.xml">Français</language>
  <language file="messages-it.xml">Italiano</language>
  <language file="messages-hu.xml">Magyarul</language>
  <language file="messages-nl.xml">Nederlands</language>
  <language file="messages-zh.xml">简体中文</language>
</languages>

Store the above instance in a file, and load it:

<instance id="languages" src="languages.xml"/>

Switch languages

Create a control to switch language:

<select1 ref="file">
   <label>?</label> 
   <itemset ref="instance('languages')/language">
      <label ref="."/>
      <value ref="@file"/>
   </itemset>
   <action ev:event="xforms-value-changed">
      <send submission="change-language"/>
   </action>
</select1>

Whenever this control gets used, and a language is selected, the instance value file gets changed, and the send action causes the following submission to be initiated, which replaces the messages instance with the translated version in the selected file:

<submission id="change-language" replace="instance" instance="m"
            method="get" serialization="none">
   <resource value="file"/>
</submission>

Result

Here it is in use:

Source

Initialising

Note that if someone changes language and then wants to change back again, you have to supply a messages-en.xml file as well, and so you may as well initialise the messages instance with that:

<instance id="m" src="messages-en.xml"/>

Whenever you need to add another language:

• translate the messages instance
• store it in a new file
• add the language to the languages file.

Easy! The XForm then works without change with the new language.