Site-wide compendia are located in the server/gnun/compendia directory of the ‘www’ web repository. There are two kinds of compendia: master.lang.po and compendium.lang.po.
The first kind, master.lang.po, can be used to simultaneously update all occurrences of the translations of a given string. Translations from this file will override the translations from article.lang.po. When master.lang.po is updated, the translations will be rebuilt. GNUN doesn’t modify this kind of compendia.
The second kind, compendium.lang.po, is updated automatically. GNUN finds strings that repeat many times in POTs of articles and collects them in compendium.pot. Then it checks all available article.lang.po files for translations of those strings and generates compendium.lang.po. This file is also used to fill missing translations, but it doesn’t override the translations from article.lang.po, and the strings coming from compendium.lang.po are always marked as “fuzzy” to prevent propagation of translations that may be wrong in a different context.
When updating compendium.pot, some strings should be excluded even though they repeat in the POT files many times—for instance, GNUN slots for translators’ notes. See The Special Slot for Translator’s Notes. They are not real translations, this is why they are likely to be different for different articles. In order to avoid including them in compendia, GNUN checks a specific file, exclude.pot, and when that file contains the string, it won’t be added to compendium.pot.