A schematic diagram is a set of schematic features (nodes, links, nodes on links, and sublinks) that has been generated using the Generate New Diagram command in ArcMap, the Create Diagram GP tool, or using the ArcGIS Schematics API.
A schematic diagram is displayed in a schematic layer, which is a composite layer composed of feature layers based on the schematic feature classes associated with the schematic diagram template.
The content, symbology, and the way the schematic diagram is generated and displayed is configured on its schematic diagram template.
A schematic diagram is stored in a geodatabase in a schematic dataset or schematic folder of the schematic dataset.
All the schematic layout algorithms and refinement tools available in ArcMap can be used to lay out a schematic diagram. Laying out a schematic diagram can be done after an edit session is opened on the diagram.
In ArcCatalog, you can only preview the schematic diagrams that have been generated.