Processor Outputs Exist

This situation is far more complex. There are 3 possible responses Insert, Replace, Append:-

Insert Mode

For this mode the processor creates its outputs but only if they don't exist. This is useful when reprocessing a files of events each of which had been partially processed. Each could safely be processed by a complete chain of processors using insert mode for any that had already be applied to the data structure would just quit.

Replace Mode

For this mode the processor erases any outputs and then processes again. This mode can be used after changing any of its inputs (including titles banks) or after changing the processor itself.

Append Mode

For this mode any existing outputs are left and new ones added. As an example: the user has generated an event and wants to see the effect of adding a second event to it so MCG_GENERATOR is called to add further seed vertices. Clearly this type of mode is useful but it only applies to ``source'' processors such as EIO_EVREAD (event merging) and MCG_GENERATOR (seed merging).

Any processor that correctly handles the cases where its inputs are missing and at least one mode when its outputs exist, is called a Standard Processor. All SNOMAN processors qualify.