Quill: an extensible system for editing documents of mixed type

A description is given of Quill, an extensible document creation system that is organized as a collection of cooperating editors, each with its own set of objects and commands. The objects implemented by the various editors can be nested without restriction, forming a hierarchical document that can be described by the Standard Generalized Markup Language (SGML). The user is presented with a ´what you see is what you get´ (WYSIWYG) view of the document in which the various objects can be directly manipulated on the display screen. A system shell ensures consistency among the editors and coordinates their foreground and background activities to ensure keystroke responsiveness. Each Quill editor is a programming object that communicate with the shell and with other editors by means of a standard set of procedures. A rigorous specification of the shell/editor interface enables additional editors to be added to the Quill system without affecting the existing editors.<>