## J.4. Documentation Authoring

SGML and DocBook do not suffer from an oversupply of open-source authoring tools. The most common tool set is the Emacs/XEmacs editor with appropriate editing mode. On some systems these tools are provided in a typical full installation.

### J.4.1. Emacs/PSGML

PSGML is the most common and most powerful mode for editing SGML documents. When properly configured, it will allow you to use Emacs to insert tags and check markup consistency. You could use it for HTML as well. Check the PSGML web site for downloads, installation instructions, and detailed documentation.

There is one important thing to note with PSGML: its author assumed that your main SGML DTD directory would be `/usr/local/lib/sgml`. If, as in the examples in this chapter, you use `/usr/local/share/sgml`, you have to compensate for this, either by setting `SGML_CATALOG_FILES` environment variable, or you can customize your PSGML installation (its manual tells you how).

Put the following in your `~/.emacs` environment file (adjusting the path names to be appropriate for your system):

    ; ********** for SGML mode (psgml)

    (setq sgml-omittag t)
    (setq sgml-shorttag t)
    (setq sgml-minimize-attributes nil)
    (setq sgml-always-quote-attributes t)
    (setq sgml-indent-step 1)
    (setq sgml-indent-data t)
    (setq sgml-parent-document nil)
    (setq sgml-exposed-tags nil)
    (setq sgml-catalog-files '("/usr/local/share/sgml/catalog"))

    (autoload 'sgml-mode "psgml" "Major mode to edit SGML files." t )

and in the same file add an entry for SGML into the (existing) definition for `auto-mode-alist`:

    (setq
      auto-mode-alist
      '(("\\.sgml$" . sgml-mode)
       ))

You might find that when using PSGML, a comfortable way of working with these separate files of book parts is to insert a proper `DOCTYPE` declaration while you're editing them. If you are working on this source, for instance, it is an appendix chapter, so you would specify the document as an “appendix” instance of a DocBook document by making the first line look like this:

    <!DOCTYPE appendix PUBLIC "-//OASIS//DTD DocBook V4.2//EN">

This means that anything and everything that reads SGML will get it right, and I can verify the document with `nsgmls -s docguide.sgml`. (But you need to take out that line before building the entire documentation set.)

### J.4.2. Other Emacs Modes

GNU Emacs ships with a different SGML mode, which is not quite as powerful as PSGML, but it's less confusing and lighter weight. Also, it offers syntax highlighting (font lock), which can be very helpful. `src/tools/editors/emacs.samples` contains sample settings for this mode.

Norm Walsh offers a major mode specifically for DocBook which also has font-lock and a number of features to reduce typing.