These files describe how a visual object is shaped, not a particular drawing. A flow schema tells you which fields a process diagram must have; resource-flow is one instance. Load a schema when you are generating or validating visual content, not when you are trying to understand a raid.
Diagram, flow, and decision-tree schemas cover process and branching. Relationship-graph schema covers nodes and edges. Spatial schema covers coordinates and regions. UI schema covers screens and elements. Pattern schema covers recurring visual motifs.
The parent visuals index is the tour. This folder is the type system for that tour.
Open visual schemas when you are producing or checking machine-readable diagrams. If you want the populated graphs, go to graphs. If you want the galactic coordinate system, go to spatial.