OpenACS Documentation Guide

By claus@arsdigita.com, with additions by Roberto Mello and the OpenACS Community

Overview of OpenACS 4.5 Documentation

ArsDigita created a good documentation ground for us to build upon. Some sections of the documentation however, lack details and examples, others simply are inexistent.Our goal is to give OpenACS a superb documentation, so that users, developers and administrators of OpenACS installations can enjoy the system.

OpenACS™ is a powerful system, with incredible possibilities and applications, but with this power comes some complexity and a learning curve that will only be atenuated by good documentation. This is what we are after.

The documentation for OpenACS™ is written using DocBook XML. The reasons why we are using DocBook are explained in more details in the Why DocBook? section. I will add the reasons why we are using Docbook XML instead of Docbook SGML:

  • Consistency. We already have a bunch of .xml files that ArsDigita wrote. Trying to re-write them to conform to the SGML DTD would be unnecessary work (I tried).
  • It does not require extra effort. Writing in XML is almost identical to SGML, with a couple extra rules. More details in the LDP Author Guide.

Why DocBook?

In order to separate content and presentation, all OpenACS documentation will be marked up to conform to the DocBook XML DTD This enables us to publish in a variety of formats and relieves each contributor of the burden of presentation, freeing him to focus on content and sharing knowledge.

Theoretically any strict DTD would have been sufficient - we could even write our own. But DocBook has been around for a while (since early 90's), it's well-tested, it's complete, it's extremely well-suited for technical documents and best of all, it's open-source. A growing community surrounds DocBook (has mailing lists) and a number of free and commercial tools are available for editing and publishing DocBook documents.

This primer walks you through the basics, and should cover the needs for 95 percent of the documentation we produce. However, you're always welcome to check out DocBook's list of elements and use more exotic features in your documents. The list is made up of SGML-elements but basically the same elements are valid in the XML DTD as long as you remember to:

  • Always close your tags with corresponding end-tags and to not use other tag minimization

  • Write all elements and attributes in lowercase

  • Quote all attributes

Tools

You are going to need the following to work with the OpenACS Docbook XML documentation:

  • Docbook XML DTD - The document type definition for XML. You can find an RPM or DEB package or you can download a zip file from the site linked from here.
  • XSL Stylesheets (docbook-xsl) - The stylesheets to convert to HTML. We have been using a stylesheet based upon NWalsh's chunk.xsl.
  • xsltproc - The processor that will take an XML document and, given a xsl stylesheet, convert it to HTML. It needs libxml2 and libxslt (available in RPM and DEB formats or from xmlsoft.org.
  • Some editing tool. A popular one is Emacs with the psgml mode. We have a intro to the PSGML Mode in Emacs as part of our documentation. You can read about other editing tools in the LDP Author Guide.

Writing New Docs

After you have the tools mentioned above, you need to define a title for your document. Then start thinking about the possible sections and subsections you will have in your document. Make sure you coordinate with the OpenACS Gatekeepers to make sure you're not writing something that someone else is already writing. Also, if you desire to use the OpenACS CVS repository, please e-mail the gatekeeper in charge of documentation.

You can look at some templates for documents (in Docbook XML) in the sources for acs-core-docs, especially the Detailed Design Documentation Template and the System/Application Requirements Template.

Document Structure

The documentation for each package will make up a little "book" that is structured like this - examples are emphasized:

    book                        : Docs for one package - templating
     |
     +--chapter                 : One section - for developers
         |
---------+------------------------------------------------------
         |
         +--sect1               : Single document - requirements
             |
             +--sect2           : Sections - functional requirements
                 |
                 +--sect3       : Subsections - Programmer's API
                     |
                    ...         : ...
    

The actual content is split up into documents that start at a sect1-level. These are then tied together in a top-level document that contains all the information above the line. This will be explained in more detail in a later document, and we will provide a set of templates for documenting an entire package.

For now you can take a look at the sources of these DocBook documents to get an idea of how they are tied together.

Headlines, Sections

Given that your job starts at the sect1-level, all your documents should open with a <sect1>-tag and end with the corresponding </sect1>.

You need to feed every <sect1> two attributes. The first attribute, id, is standard and can be used with all elements. It comes in very handy when interlinking between documents (more about this when talking about links in the section called “Links”). The value of id has to be unique throughout the book you're making since the id's in your sect1's will turn into filenames when the book is parsed into HTML.

The other attribute is xreflabel. The value of this is the text that will appear as the link when referring to this sect1.

Right after the opening tag you put the title of the document - this is usually the same as xreflabel-attribute. E.g. the top level of the document you're reading right now looks like this:

      <sect1 id="docbook-primer" xreflabel="aD DocBook Primer">
      <title>aD DocBook Primer</title>

      ...

      </sect1>
    

Inside this container your document will be split up into <sect2>'s, each with the same requirements - id and xreflabel attributes, and a <title>-tag inside. Actually, the xreflabel is never required in sections, but it makes linking to that section a lot easier.

When it comes to naming your sect2's and below, prefix them with some abbreviation of the id in the sect1 such as requirements-overview.

Code

For displaying a snippet of code, a filename or anything else you just want to appear as a part of a sentence, we will use the tag <computeroutput>. This takes the place of the HTML-tag <code>

For bigger chunks of code such as SQL-blocks, the tag <programlisting> is used. Just wrap your code block in it; mono-spacing, indents and all that stuff is taken care of automatically.

Links

Linking falls into two different categories: inside the book you're making and outside:

1. Inside linking, cross-referencing other parts of your book

By having unique id's you can cross-reference any part of your book with a simple tag, regardless of where that part is.

Check out how I link to a subsection of the Developer's Guide:


	    Put this in your XML:

	    - Find information about creating a package in
	    <xref linkend="packages-making-a-package"></xref>.


	    And the output is:

	    - Find information about creating a package in 
	    Making a Package

	  

Note that even though this is an empty tag, you have to either:

  1. Provide the end-tag, </xref>, or

  2. Put a slash before the ending-bracket: <xref linkend="blahblah"/>

If the section you link to hasn't a specified xreflabel-attribute, the link is going to look like this:


	    Put this in your XML:

	    - Find information about what a package looks like in 
	    <xref linkend="packages-looks"></xref>.


	    And the output is:

	    - Find information about what a package looks like in 
	    the section called “What a Package Looks Like”

	  

Note that since I haven't provided an xreflabel for the subsection, packages-looks, the parser will try its best to explain where the link takes you.

2. Linking outside the documentation

If you're hyper-linking out of the documentation, it works almost the same way as HTML - the tag is just a little different (<ulink>):

<ulink url="http://www.oracle.com/">Oracle Corporation</ulink>

....will create a hyper-link to Oracle in the HTML-version of the documentation.

NOTE: Do NOT use ampersands in your hyper links. These are reserved for referencing entities, which is exactly how you'll make an ampersand: &amp;

Graphics

NOTE: Currently this section currently only takes HTML-output into consideration - not a printed version

Another Note: Also, it's still not a 100 percent sure that this is how we are going to do it, so if you want to start converting your documents right away, start out with the ones without graphics ;)

To insert a graphic we use the elements <mediaobject>, <imageobject>, and <imagedata>. The news is that you have to provide two versions of all your graphics - one for the Web (probably a GIF or a JPEG) and one for print (EPS). Finally you should provide a brief description wrapped in <textobject> - in HTML this will be the ALT text.

      <mediaobject>
      <imageobject>
      <imagedata fileref="../images/rp-flow.gif" format="GIF" align="center"/>
      </imageobject>
      <imageobject>
      <imagedata fileref="../images/rp-flow.eps" format="EPS" align="center"/>
      </imageobject>
      <textobject>
      <phrase>This is an image of the flow in the Request Processor</phrase>
      </textobject>
      </mediaobject>
    

Put your graphics in a separate directory ("images") and link to them only with relative paths.

Lists

Here's how you make the DocBook equivalent of the three usual HTML-lists:

1. How to make an <ul>

Making an unordered list is pretty much like doing the same thing in HTML - if you close your <li>, that is. The only differences are that each list item has to be wrapped in something more, such as <para>, and that the tags are called <itemizedlist> and <listitem>:

	    <itemizedlist>
	    
	    <listitem><para>Stuff goes here</para><listitem>
	    <listitem><para>More stuff goes here</para><listitem>

	    </itemizedlist>
	  
2. How to make an <ol>

The ordered list is like the preceding, except that you use <orderedlist> instead:

	    <orderedlist>
	    
	    <listitem><para>Stuff goes here</para><listitem>
	    <listitem><para>More stuff goes here</para><listitem>

	    </orderedlist>
	  
3. How to make a <dl>

This kind of list is called a variablelist and these are the tags you'll need to make it happen: <variablelist>, <varlistentry>, <term> and <listitem>:

	    <variablelist>
	    
	    <varlistentry>
	    <term>Heading (<dt>) goes here</term>
	    <listitem><para>And stuff (<dd>)goes here</para><listitem>
	    </varlistentry>

	    <varlistentry>
	    <term>Another heading goes here</term>
	    <listitem><para>And more stuff goes here</para><listitem>
	    </varlistentry>

	    </variablelist>
	  

Tables

DocBook supports several types of tables, but in most cases, the <informaltable> is enough:

      <informaltable frame="all">
      <tgroup cols="3">
      <tbody>

      <row>
      <entry>a1</entry>
      <entry>b1</entry>
      <entry>c1</entry>
      </row>

      <row>
      <entry>a2</entry>
      <entry>b2</entry>
      <entry>c2</entry>
      </row>

      <row>
      <entry>a3</entry>
      <entry>b3</entry>
      <entry>c3</entry>
      </row>

      </tbody>
      </tgroup>
      </informaltable>
    

With our current XSL-style-sheet, the output of the markup above will be a simple HTML-table:

a1 b1 c1
a2 b2 c2
a3 b3 c3

If you want cells to span more than one row or column, it gets a bit more complicated - check out <table> for an example.

Emphasis

Our documentation uses two flavors of emphasis - italics and bold type. DocBook uses one - <emphasis>.

The <emphasis> tag defaults to italics when parsed. If you're looking for emphasizing with bold type, use <emphasis role="strong">.

Indexing Your DocBook Documents

Marking up index-words may not have any importance for the HTML-output, but in order to make it easier to make a nice print-version of the documentation, you should mark up words in your documents that you would like to see show up in an index one day.

Use <indexterm>, <primary> and <secondary> for this. See these links for an explanation.

Converting to HTML

Note

This section is quoted almost verbatim from the LDP Author Guide.

Once you have the Docbook Tools installed, you can convert your xml documents to HTML (or other formats. Let me know if you are able to convert to other formats).

With the DocBook XSL stylesheets, generation of multiple files is controlled by the stylesheet. If you want to generate a single file, you call one stylesheet. If you want to generate multiple files, you call a different stylesheet.

To generate a single HTML file from your DocBook XML file, use the command:

bash$  xsltproc -o outputfilename.xml /usr/share/sgml/docbook/stylesheet/xsl/nwalsh/html/html.xsl filename.xml
    

Note

This example uses Daniel Veillard's xsltproc command available as part of libxslt from http://www.xmlsoft.org/XSLT/. If you are using other XML processors such as Xalan or Saxon, you will need to change the command line appropriately.

To generate a set of linked HTML pages, with a separate page for each <chapter>, <sect1> or <appendix> tag, use the following command:

bash$  xsltproc /usr/share/sgml/docbook/stylesheet/xsl/nwalsh/html/chunk.xsl filename.xml
    

Further Reading

  • The LDP Author Guide has a lot of good information, a table of docbook elements and their "look" in HTML and lots of good links for tools.
  • David Lutterkort wrote an intro to the PSGML Mode in Emacs

  • For checking if your document is well-formed, James Clark's free Java parser, XP, is recommended. (note that it is not a validating parser, but as long as you follow the guidelines set forth in this document, your XML will validate)

  • DocBook Tool for Linux: Let's you convert your docbook documents to a number of formats. Sometimes it's nice to see how you stuff looks. NOTE: I only got these to work with Docbook SGML, NOT with Docbook XML. If you are able to make it work with our XML, please let us know.

  • AptConvert from PIXware is a Java editor that will produce DocBook documents and let you transform them into HTML and PDF for a local preview before you submit.

  • In the process of transforming your HTML into XML, HTML tidy can be a a handy tool to make your HTML "regexp'able". Brandoch Calef has made a Perl script that gets you most of the way.

Revision History

Document Revision # Action Taken, Notes When? By Whom?
0.3 Added OpenACS information, updated tools, added extra links and added info to the Publishing section. 12/24/2001 Roberto Mello
0.2 Changed recommendation from <phrase> to <emphasis role="strong"> 01/19/2000 Claus Rasmussen
0.1 Creation 12/2000 Claus Rasmussen