Thank you all for your replies they have been very helpful.

@Koen - Our intention is primarily for auditing but I can see scenarios where it would be useful for reporting. For instance the CFO may wish to see a summary of the ticket data from just System A, just System B or perhaps a summary of A and B omitting systems C & D.

@below86 - Yes, it is certainly easier to keep track from the beginning rather than adding later. We will definitely keep track and probably with a table as you Cliff & Lempster suggested.

@Cliff, & Lempster - I too like the idea of a separate table I just wasn't sure if it was the right way to go. I have a meeting with the vested parties this afternoon and if they agree too we'll add it as a separate table with a foreign key into each of our Ticket Fact as well as Location, Ticket Type, and Event dimension tables.