While processing an SGML document the document may refer to external data. This occurs in three places: external parameter entities, normal external entities and the DOCTYPE declaration. The current version of this tool deals rather primitively with external data. External entities can only be loaded from a file.
Two types of lines are recognized by this package:
DOCTYPE doctype file
PUBLIC "Id " file
The parser loads the entity from the file specified as file. The file can be local or a URL.