Document convergence in an interactive formatting system
by D. D. Chamberlin
One of the most complex aspects of document formatting is the processing of references to remote objects such as headings and figures. In the case of a forward reference to an object that occurs later in the document, two formatting passes are usually needed before the document converges to a stable state. Some documents require more than two passes to converge, and cases are known of documents that never converge but oscillate between two unstable states. This paper describes the techniques used for resolving references and detecting document convergence by the Interactive Composition and Editing Facility, Version 2 (ICEF2). ICEF2 is an interactive formatting system that allows users to move about in a document, editing and reformatting pages. The concepts of formatting pass and document convergence are discussed in the context of interactive formatting. A description is given of the ICEF2 data store, a small relational database manager with special features for detecting document convergence. A sample ICEF2 style definition is discussed to illustrate how ICEF2 deals with document elements whose appearance depends on their location on the page.