METHOD AND SYSTEM TO HANDLE INCLUSION OF EXTERNAL FILES INTO A DOCUMENT PROCESSING LANGUAGE

An apparatus for controlling printing or display of documents represented in a structured hierarchal page description language. Documents are provided as a document data stream which can include references to external references and external data declarations which can be incorporated into the document by the content processor. Documents are defined by a prologue section which may contain definitions and declaratory commands, with content portions containing specific tokens or command for specific images. The document data stream has a hierarchal structure. A means to provide external declarations is provided which will process external declarations as if the external declaration which can be stored on a separate device were part of the original document data structure. The storage of the references to the external declarations is accomplished in a tree linked stack structure with a last in first out arrangement which allows for a faster search order of external declarations. The tree linked stack structure further allows for the correct external declaration to be associated with a given reference thereto, even if different external declarations within the document data stream might have the same name. The context of the document data stream and the level in which a call is made determines the exact external declaration which is being referenced. This provides an incorporation by reference ability to a document data stream.