Way back in the early days of the web, around 2004, I wrote a templating system that used the file system for inheritance. I think Fred Toth originally conceived of the technique.
In the directory /A/B/C you place the template M with content
Hello [%include N%]
You then have the templating system expand /A/B/C/M. It would execute the directive [%include N%] to include the template N by looking up the directory tree, in order, /A/B/C/N, /A/B/N, and /A/N, and using the first N it found. You would place common templates (eg headers) and default content (eg company name) in the upper directories and "override" them in the lower directories. It worked really well for the mostly static sites my department was creating.
I have not seen something like this elsewhere. You can, however, achieve the same effect by manipulating your templating system's template search path per output document.
The system came to be called Trampoline and it has a Perl and a Java partial reimplementation. The implementations are in the Clownbike project at Source Forge. None of the templates Clownbike used made it to Source Forge, unfortunately. Those became the proprietary web sites our customers were paying for. Galley, an internal project, seems to have some.
I have no idea if any of this code still works. I am sure to be embarrassed by the code's quality! Some quiet, rainy day this winter perhaps I will try running it.
