A reference to the schema to manipulate
Schema contains one or more databases, which each may have info about one or more tables, which each may have info about one or more columns, which each have info about whether it is a primary key, null is allowed, its type, etc.
SchemaColumn contains information about one column (its attributes).
SchemaDatabase contains information about one database (its tables).
undocumented class
Takes a schema (and config) and runs through the schema in an effort to detect foreign keys that may have been missed (or simply weren't specified at the database level).
The base SchemaRelationship class contains and provides accessors to the local table object and key and the reference (foreign) table object and key.
SchemaRelationshipHasMany adds methods to pull it's "has one" counterpart.
SchemaRelationshipHasOne adds methods to pull it's "has many" counterpart.
SchemaTable contains information about one table (its columns).