TYPO3 Core

Current localisation packages are fetched from (a mirror of) http://translation.typo3.org/l10n_ter/.

In order for a TYPO3 website to be able to fetch the localisation packages, we have to publish them to a special directory structure and additionally create an index as XML.

The directory structure starts with two levels corresponding to the first 2 letters of the extension name, for instance, if an extension is "sphinx" we start with a directory "s" and a directory "p":

http://translation.typo3.org/l10n_ter/
`-- s
    `-- p
        `-- sphinx-l10n
            |-- ...
            |-- sphinx-l10n-de.zip
            |-- sphinx-l10n-dk.zip
            |-- sphinx-l10n-el.zip
            |-- sphinx-l10n-eo.zip
            |-- sphinx-l10n-es.zip
            |-- ...
            `-- sphinx-l10n.xml

The file sphinx-l10n.xml in turn is a simple index containing the creation date and the md5 hash of each zip file:

<TERlanguagePackIndex>
    <meta>
        <timestamp>1436916201</timestamp>
        <date>2015-07-15 01:23:21</date>
    </meta>
    ...
    <languagePackIndex>
        <languagepack language="de">
            <md5>3929d1aac266ab58e7bd3fdb1dbcd905</md5>
        </languagepack>
        <languagepack language="dk">
            <md5>817e919e0f91bf1a6e01cd68f96d2b20</md5>
        </languagepack>
        <languagepack language="el">
            <md5>01447d563e42539dd8eb4cdc36941c4c</md5>
        </languagepack>
        <languagepack language="eo">
            <md5>e8f24382346fac2162a69766aa5efdff</md5>
        </languagepack>
        <languagepack language="es">
            <md5>4100432e5e9914561bf593d2f03f8f65</md5>
        </languagepack>
    </languagePackIndex>
    ...
</TERlanguagePackIndex>

Until TYPO3 6.2 LTS, packages contain both legacy ll-XML localisation files (locallang*.xml) and XLIFF ones (locallang*.xlf), as well as outdated labels since it was not allowed to remove obsolete labels in order to prevent translations to "disappear" from older TYPO3 versions when fetching updated localisation packages.

As of TYPO3 7 LTS, it is possible to move localisation files and remove outdated labels. A special zip package is thus needed, containing only required labels and files, and taking their actual target directory into account.

Since it is not possible to change the directory structure of localisation packages nor does it make sense to reinvent the wheel, it is suggested to keep current directory and file structure and create additional packages for TYPO3 v7, v8, ... by using a <extension>-l10n-<lang>.v7.zip, <extension>-l10n-<lang>.v8.zip file name and have a dedicated language pack index using the same logic, with <extension>-l10n.v7.xml.

The Languages backend module will have to look for dedicated localisation packages (ideally only for system extensions). I would suggest NOT to implement any fallback to previous package versions in case they are not yet available since this should be a matter of hours/days to get v8, v9, ... dedicated packages anyway.