The whole point of po4a is to make the documentation translation maintainable. The idea is to reuse the gettext methodology to this new field. Like in gettext, texts are extracted from their original locations in order to be presented in a uniform format to the translators. The classical gettext tools help them updating their works when a new release of the original comes out. But to the difference of the classical gettext model, the translations are then re-injected in the structure of the original document so that they can be processed and distributed just like the English version.

Thanks to this, discovering which parts of the document were changed and need an update becomes very easy. Another good point is that the tools will make almost all the work when the structure of the original document gets fundamentally reorganized and when some chapters are moved around, merged or split. By extracting the text to translate from the document structure, it also keeps you away from the text formatting complexity and reduces your chances to get a broken document (even if it does not completely prevent you to do so).