1. A data processing device comprising: a memory that stores one or more data sets and programs including one or more application programs; and a processor that executes the programs to function as: an object generator that generates an object containing one or more procedures of operation using at least one of the one or more data sets, the one or more procedures being called and executed by the processor in accordance with an application program stored in the memory, a data access manager that prohibits any access to the one or more data sets by the processor running the application program stored in the memory without calling and executing a procedure contained in an object generated by the object generator, and an object generation manager that determines whether to generate a perfect encapsulated object or an imperfect encapsulated object based on reliability of one application program among the one or more application programs, the perfect encapsulated object being an object containing no procedures of operation making a specific data set among the one or more data sets accessible by the processor running any one of the one or more application programs, the object generation manager allows the object generator to generate, in accordance with the one application program among the one or more application programs, the imperfect encapsulated object that is an object containing procedures of operation making the specific data set among the one or more data sets accessible by the processor running any one of the one or more application programs, if it is determined to generate an imperfect encapsulated object.