PURPOSE: To add a function to a printer by speedily fetching an external declaration to a document data stream, correcting the document data stream while using the external data declaration, and using the external declaration for structured environments.

CONSTITUTION: External data 72 are fetched into an original document 70 so as to be printed or displayed just as a part of the document. The document is applied as the document data stream of hierarchical structure but this can include external reference and reference to the external data declaration. The reference to the external declaration is stored by first-in first-out tree link stack structure.