Models depending on a particular PDR version
A model that uses a particular language construct, of a particular function of one of the libraries, requires the version of the PDR having those constructs and functions in order to function correctly. Should an end user install such a model (or upgrade to that version of the model) without also upgrading her PDR, the model will not function properly.
However, we assume that end users will have no control over the version of the PDR the run. We make it so that they download and start using the newest version as soon as possible. This problem should therefore not occur.
There is one exception and that is the remote case that an end user starts a session before the PDR update and during that session wants to start using the model version that needs the new PDR. We do not provision for this exceptional case: all the end user has to do is to restart MyContexts to solve the problem.