Data model compiler selectively using a reference store of labelled program components within a common class

A computer system comprising:

• data processing means connected to:
• (i) memory means having a control program stored therein;
• (ii) a store;
• (iii) an input interface;
• (iv) an output interface;
• and
• (v) a reference store containing a plurality of pre-defined program components each having a plurality of fields, wherein each component has a field containing a label unique to that component and wherein at least one component has a field containing information defining a computation to be performed;
• wherein the data processing means are arranged, in operation, under control of said control program:
• (a) in response to user selection via the input interface to copy selected ones of said program components into the store;
• (b) in response to user commands via the input interface to enter into the store link information determining the transfer of data from a field of one program component stored in the store into a field of another such component;
• (c) to perform computation as defined by the program components and link information stored in the store and to output results thereof via the output interface;
• and
• (d) in response to the label field of a program component stored in the store, to compare a field of the component with a corresponding field of the program component stored in the reference store and having the same label, and to identify a field shown by said comparison to be different;
• wherein each component, at least in the reference store, having tag fields each of which identifies a field of the component as being of one of a plurality of classes of field, and
• wherein the said comparison is performed only for fields thereby indicated as belonging to a particular class or classes.