Hello Dan,
If these "data exchanges" are important enough to be managed in ServiceNow, I would recommend using a specific CI Class to document and keep track of these.
I've been involved in cases where these have been defined as "Integrations" or "Integration use cases". The "Integration" CI class would include details about the data exchange and technicalities related to implementation. This way you could formally describe things like sequence, direction, payload, integration method, etc. And of course, use CI relationships to connect these Integration CIs to Application Service or Business Application records related to them.
This requires more data maintenance work, than a simple link between applications, but from impact analysis and integration management point-of-view, it's probably worth it. Pro Tip! You don't have to define all "integrations" like this, but only the once that matter the most.
Here's an example diagram about the "Integration" class and how it could relate to other classes.
Cheers,
--Mikko
