According to the concept of object-orientation, similar objects in the application domain are grouped into related types. Each of these types have a name, an internal representation, and behavior.
Consequently, there is an important synergy between UDTs, UDFs, and LOBs. An application type with a complex data structure and behavior is modeled as a UDT that is internally represented as a LOB, with its behavior implemented by UDFs. As described in Using Triggers in an Active DBMS, the rules governing the semantic integrity of your application type will be represented as constraints and triggers. To have better control and organization of your related UDTs and UDFs, you should keep them in the same schema.