The data objects required for some of the methods specified are incompatible with each other. For example, all methods that ...

The data objects required for some of the methods specified are incompatible with each other. For example, all methods that use a user-defined type as a parameter must use the same user-defined type in the other methods (or not use a user defined type). That is, if the Insert method takes a single parameter of type Product, the Update method must also take a single parameter of type Product, not of type Customer.