Here is the sample message we are testing
ISA>00>1234567890>00>1234567890>28>PPPPP >28>SSSSSS >100624>1430>^>00501>000000001>0>P>+
...although please note, the TA1 may appear multiple times.
I didn't realize what you were saying about where acknowledgements can happen...so I guess you're right that the SpecificationFinder might not need to change.
We have created the xml for the 999 file, and I'll post that shortly, in case it helps.
As for a way of providing acknowledgements, my gut programmer instinct says to create an interface called IAcknowledgementProvider or create an event on the Parser (or something else)
event EventHandler<AcknowledgementRequestedEventArgs> AcknowledgementRequested
that allows the parser to request an acknowledgement to generate.
...But without being as close to the code as you are, I'm sure your intuition would be better on this.