[TYPO3-english] TYPO3 6.2.x: translating mechanisms within and without extensions

[Bert Hiddink [BENDOO e-work solutions]]

Hello,

I would like to create a XML-language file I can use within my site 
and/or extensions.

What I understood from here:
http://stackoverflow.com/questions/20775407/how-to-use-xliff-outside-an-extension-in-typo3
...this could be done like this in Fluid:

<f:translate 
id="LLL:typo3conf/ext/news/Resources/Private/Language/locallang.xml:more-links" 
/>	

...
	<data type="array">
		<languageKey index="default" type="array">
			<!-- Common -->
			<label index="more-link">Read more</label>
...

Apparently, this works:
<f:translate 
id="LLL:typo3conf/ext/news/Resources/Private/Language/locallang.xml:more-links" 
/>	

...since this gives back "Read more".

However, if I change the index-key to "my-var":

<f:translate 
id="LLL:typo3conf/ext/news/Resources/Private/Language/locallang.xml:my-var" 
/>	

..it returns nothing...

So what is happening here? Is News reading this language field from 
another file? If yes, from where? And why could I not add custom-fields?

Any ideas?

Thanks in advance!

Regards,
Bert