A method, apparatus, and article of manufacture for providing to a signature hash for checking versions of abstract data types. An identifier is constructed for the abstract data type that is substantially unique to the abstract data type, wherein the identifier comprises a concatenation of various attributes for the abstract data type. The constructed identifier is hashed to generate a signature hash value for the abstract data type, which is then stored both in the database and a class definition for the abstract data type. When the class definition is instantiated as a library function, it accesses the abstract data type from the database, and compares the signature hash value from the database and the signature hash value from the class definition in order to verify that the class definition is not outdated. The class definition is outdated when the abstract data type has been altered without the signature hash value being re-generated and re-stored in the database and the class definition.