The Scenarios XSD schema defines all messages and envelope elements that are necessary for the real-life application of FIFA Connect Data in specific use-cases/scenarios. An end-user applying the FIFA Connect Data technically needs to include/use only the Scenarios XSD.

The Scenarios XSD itself includes/uses all other XSDs within the Football Connect Data standard, as these contain data model definitions for any real-life scenario.
Scenarios XSD elements are adjusted to scenarios, and as such, are more open to future additions/alterations, than other parts of FIFA Connect Data.