Definition of an Asynchronous Processor

An Asynchronous Processor is a Standard Processor whose actions can be undone by calling its Delete Outputs routine. Such processors support both Insert and Replace modes. Calls to Asynchronous Processors can be mixed in any order and allows the user to process and reprocess as required.

Such processors can form the basis of an interactive analysis program. For example suppose there is a chain of processors called A, B, C and D with each taking the outputs of the previous processor as its inputs. In an interactive session the user first wants to run A, B, C and D and then make some changes and reprocess from some selected point, say from processor C. To do this the processors are first called in order using Insert mode to get the data structure ready. Now all that has to be done during interaction is that the control program does two things:-

• First calls the processor designated by the user in Replace mode. In our example it is C that is called.

• Then calls all processors in the order A, B, C and D in Insert mode.

In our example calling C will results in D's output being deleted and C's replaced. Now the Insert mode calls to A, B and C will have no effect (their outputs already exist) and the call to D will generate its outputs.