01 / CONTEXT
Define a record before exchanging it.
Imagine two tools referring to the same appointment. One may store a local time, while the other expects a time with an explicit time zone. Both can contain a plausible value and still describe different moments. Naming a field “appointment time” does not resolve that difference.
A useful record description identifies the meaning of each field, its allowed values, and whether it can be empty. It also explains how a record is recognized over time. These definitions help people discuss the exchange without needing to inspect every implementation detail.
02 / RELATIONSHIPS
Identify responsibility for changes.
If two systems can edit the same information, someone needs to decide which system is responsible for which part. An updated label in one place does not necessarily mean every connected tool has received it. Timing and ownership are separate questions.
Consider what happens when information arrives late, contains an unknown value, or refers to a record that no longer exists. The appropriate response depends on the context. Keeping the previous value, requesting review, and rejecting an update have different consequences for the person relying on the information.
03 / REVIEW
Make the boundary understandable.
A short exchange specification can describe the source, destination, field meanings, and expected response to an unsuccessful transfer. A few invented records are often enough to expose unclear assumptions without sharing real customer information.
Review the information needed for the task and avoid transferring additional fields simply because they are available. Record how an issue can be recognized and who should investigate it. The aim is a connection people can explain and maintain, rather than a diagram that only shows arrows between boxes.