7 . 3 Multiple Use
Facilitating document interchange is only one reason to use standards. Another compelling reason to use a standard document representation is that it allows you to use document content in more than one way.
The proper use of standards enables the creation of documents that may be used in several ways: for printing, presentations, and on-line viewing. Several products can be based on a single repository of content. It is possible, indeed desirable, to automate the usually manual cutandpaste process. A CD-ROM electronic encyclopedia and the printed version can be created from the one collection of information.(10) Document components can be extracted for the purpose of generating automatic summaries. Indexes and automatic cross references can be created with the consistent use of tagging schemes.
In the CALS domain, a significant project that is addressing the issue of multiple use is the Interactive Electronic Technical Manual (IETM) project. The IETM project is concerned mainly with the delivery and use of on-line hypertext/hypermedia documents. However, it will be possible to generate paper copies of the document from the same electronic information.
7 . 3 . 1 Data Preparation
The process of preparing information for distribution in a number of electronic forms is called data preparation.
The creation of electronic documents invariably requires a clear, organized structure for the data. The tagging and markup mechanisms used by SGML and procedural markup systems greatly aid the data preparation process. Usually, the data preparation involves identifying certain structural elements of the document. The elements chosen can become a form of outline that can be used as a user interface mechanism for on-line browsers. The Table-of-Contents used as a front end for a document is common and useful.
Key tagged elements can also be used to create automatic cross-references. Creating semantically meaningful links across a large collection of text is a significant authoring task, which should not be underestimated. Tags and markup can be used to jumpstart the process by automating some of the link creation.
7 . 3 . 2 TeX's Weave and GNU Emacs' Texinfo
Two interesting and practical examples of multiple use are TeX and GNU Emacs. TeX is one of the most widespread batchoriented typesetting languages. (See Section 4 . 1 Types of Document Processors in Chapter 4 Form and Function of Document Processors.) GNU (Gnu's Not Unix) Emacs is one of the popular text editing environments for UNIX and is available for free from the Free Software Foundation (FSF). Both systems use information for two different purposes.
Another format with multiple uses is the texinfo format used in GNU's Emacs. GNU Emacs is as much a user's environment as it is a text editor. Just name a bizarre, complicated, baroque function you wish to accomplish in a few keystrokes, and Emacs probably has a builtin function for just such a purpose.
One of the more interesting features of Emacs is the info system. It provides Emacs users with a robust hypertext help system. It is an Emacs mode, which allows the interactive browsing of a treestructured collection of documentation. The info system is used as one of the principal means of documenting many of the internal Emacs modes, as well as just about anything else you like. Paper documentation is also quite nice: so, in order to kill two birds with one stone, the GNU folks have created the texinfo format. Texinfo is a collection of specific TeX macros. The texinfo document can be run through TeX to create a typeset document for printing. In addition, the texinfo document can be processed through a texinfo program, an Emacs function, to create an info system online document. The bottom line is that an author can create a single document that can be printed with highquality typesetting and browsed online. Clever folks!
