Philosophy of PDI

Similarly to aspect-oriented programming, PDI distinguishes between core concerns and cross-cutting concerns.

Core concerns are the aspects of the code that fulfill its main goal. We consider as core concerns of a simulation code the aspects handled in the main loop that generate elements needed as input of the next iteration of the loop.

Cross-cutting concerns are the aspect of the code that are not core concerns. We consider as cross-cutting concerns of a simulation code:

• the aspects handled before the simulation main loop such as parameters reading, data initialization, etc,
• the aspects handled after the simulation main loop, such as result post-processing, storage to disk, visualization, etc,
• the aspects handled during the simulation main loop, but whose execution is not required for the next iteration of the loop, such as fault tolerance, logging, etc.

The simulation could run with none of the cross-cutting concerns implemented (even if this would be completely useless with no result ever saved). The deactivation of a core concern on the other hand would lead to a failure of the simulation.

PDI supports calling libraries from the specification tree instead of from the code. This is well suited for cross-cutting concerns but means that the code has no control over what and how these aspects are handled which does not fit the needs of core concerns.