You will have to specify the imported MPS IDL files on the command-line of a separate invocation of the mpsidl compiler. Namespaces help avoid problems where two separate meanings are attached to the same name. Namespaces are hierarchic - you can nest a namespace within a namespace. All identifiers in an MPS IDL file are bound within a namespace. Structures are used in MPS IDL to transfer a collection of information of various types using a single object.
All data types are legal as parameters and return types.
Variable declarations are used to define the body of structures.