A system is a reflection of the understanding of the domain the system runs in.
The data that the system uses and creates is the real value of the system.
Understanding the data in terms of the system and the context that the system runs in is an important perspective.
If the model for the data and how the data fits together is unclear, this lack of clarity will be reflected in the system.
Don’t overlook the value of entity-relationship diagrams, data flows, and business rules in any business analysis engagement.