Currently property files can be read from a few sources. However in the current situation the property files are mostly read from inside the deployed application (insde the war file). In an enterprise situation it is practically never the case that the properties are the same in DTAP (Development, Test, Acceptance, Production) environment. For instance the database most likely is different in any of these environment.
To support this it should be possible to override a minor subset of all the available properties. In this situation external (outside war) and internal (inside war) are merged together in one set of property files used by Isis. (see also
It is possible to achieve this using the classpath but that is quite a burden. Using a special context parameter (in web applications) is the easiest and most transparent solution.