The model's schema. It defines allowed and disallowed structures of nodes as well as nodes' attributes. The schema is usually defined by features and based on them the editing framework and features make decisions how to change and process the model.
A schema context — a list of ancestors of a given position in the document.
A simplified version of
SchemaItemDefinitionafter compilation by the schema. Rules fed to the schema by
extendmethods are defined in the
SchemaItemDefinitionformat. Later on, they are compiled to
SchemaCompiledItemDefitionso when you use e.g. the
getDefinitionmethod you get the compiled version.