Currently, when referencing different sections of the same book, the whole source always needs to be repeated, and the references section may be cluttered by repeated appearances of the same source, with only slight variations. So this is an attempt to bundle the info.
**How it should work**
The extends parameter gets a string that corresponds to a previously defined reference. e.g. a reference that was named with `name="animal"` can then be specified through `<ref extends="animal">`.
`<ref extends="animal"> Page 25 </ref>` should then lead to "Page 25" being printed in the references section, below the definition of the "animal" source, and with an indent
The extends-attribute inherits the group parameter from the reference it is extending. I.e. <ref name="A" group="G"> info </ref> can be extended by <ref extends="A"> details </ref> and the details will also be shown in group G.
Refined refs can also have a name. e.g. If there was `<ref refines="animal" name="animalpage25"> Page 25 </ref>`, `<ref name="animalpage25" />` would also link to the refined reference.
It is not possible to refine a reference more than once (i.e. 1.1.1 never exists).
This change needs to be implemented both for parsoid and the cite extension (see subtasks (which are to come ;) )
This is a concrete implementation task for the proposal that was discussed in T138601.
The wish to improve the referencing of multiple parts of the same source was part of the German-speaking community's technical wishlist in 2013, 2015 and of the international technical wishlist in 2015. For more info, see T100645.