Gentoo Linux XML Guide

1. Guide basics

The guide XML syntax is lightweight yet expressive, so that it is easy to learn yet also provides all the features we need for the creation of web documentation. The number of tags is kept to a minimum -- just those we need. This makes it easy to transform guide into other formats, such as DocBook XML/SGML or web-ready HTML.

The goal is to make it easy to create and transform guide XML documents.

Further Resources

If you are planning on contributing documentation to Gentoo, or you want to test GuideXML, please read the Tips and Tricks which contains tips and tricks for documentation development.

2. Guide XML

Basic structure

Now that you know how to transform guide XML, you're ready to start learning the GuideXML syntax. We'll start with the the initial tags used in a guide XML document:

Code Listing 2.1: The initial part of a guide XML document

<?xml version='1.0' encoding="UTF-8"?>
<!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
<guide link="relative_link_to_your_guide">
<title>Gentoo Linux Documentation Guide</title>
<author title="Author">
  <mail link="[email protected]">Your Name</mail>
</author>

<abstract>
This guide shows you how to compose web documentation using
our new lightweight Gentoo GuideXML syntax.  This syntax is the official
format for Gentoo Linux web documentation, and this document itself was created
using GuideXML.
</abstract>

<!-- The content of this document is licensed under the CC-BY-SA license -->
<!-- See http://creativecommons.org/licenses/by-sa/2.0 -->
<license/>

<version>1.0</version>
<date>29 Mar 2001</date>

On the first, line, we see the requisite tag that identifies this as an XML document. Following it, there's a <guide> tag -- the entire guide document is enclosed within a <guide> </guide> pair. Next, there's a <title> tag, used to set the title for the entire guide document.

Then, we come to the <author> tags, which contain information about the various authors of the document. Each <author> tag allows for an optional title= element, used to specify the author's relationship to the document (author, co-author, editor, etc.). In this particular example, the authors' names are enclosed in another tag -- a <mail> tag, used to specify an email address for this particular person. The <mail> tag is optional and can be omitted, and no more than one <author> element is required per guide document.

Next, we come to the <abstract>, <version> and <date> tags, used to specify a summary of the document, the current version number, and the current version date (in DD MMM YYYY format) respectively. This rounds out the tags that should appear at the beginning of a guide document. Besides the <title> and <mail> tags, these tags shouldn't appear anywhere else except immediately inside the <guide> tag, and for consistency it's recommended (but not required) that these tags appear before the content of the document.

Finally we have the <license/> tag, used to publish the document under the Creative Commons - Attribution / Share Alike license as required by the Documentation Policy.

Chapters and sections

Once the initial tags have been specified, you're ready to start adding the structural elements of the document. Guide documents are divided into chapters, and each chapter can hold one or more sections. Every chapter and section has a title. Here's an example chapter with a single section, consisting of a paragraph. If you append this XML to the XML in the previous excerpt and append a </guide> to the end of the file, you'll have a valid (if minimal) guide document:

Code Listing 2.2

<chapter>
<title>This is my chapter</title>
<section>
<title>This is section one of my chapter</title>
<body>

<p>
This is the actual text content of my section.
</p>

</body>
</section>
</chapter>

Above, I set the chapter title by adding a child <title> element to the <chapter> element. Then, I created a section by adding a <section> element. If you look inside the <section> element, you'll see that it has two child elements -- a <title> and a <body>. While the <title> is nothing new, the <body> is -- it contains the actual text content of this particular section. We'll look at the tags that are allowed inside a <body> element in a bit.

Note: A <guide> element can contain multiple <chapter> elements, and a <chapter> can contain multiple <section> elements. However, a <section> element can only contain one <body> element.

An example <body>

Now, it's time to learn how to mark up actual content. Here's the XML code for an example <body> element:

Code Listing 2.3

<p>
This is a paragraph.  <path>/etc/passwd</path> is a file.
<uri>http://www.gentoo.org</uri> is my favorite website.
Type <c>ls</c> if you feel like it.  I <e>really</e> want to go to sleep now.
</p>

<pre>
This is text output or code.
# <i>this is user input</i>

Make HTML/XML easier to read by using selective emphasis:
<foo><i>bar</i></foo>

<codenote>This is how to insert an inline note into the code block</codenote>
</pre>

<note>
This is a note.
</note>

<warn>
This is a warning.
</warn>

<impo>
This is important.
</impo>

Now, here's how this <body> element is rendered:

This is a paragraph. /etc/passwd is a file. http://www.gentoo.org is my favorite website. Type ls if you feel like it. I really want to go to sleep now.

Code Listing 2.4

This is text output or code.
# this is user input

Make HTML/XML easier to read by using selective emphasis:
<foo>bar</foo>

// This is how to insert an inline note into the code block

Note: This is a note.

Warning: This is a warning.

Important: This is important.

The <body> tags

We introduced a lot of new tags in the previous section -- here's what you need to know. The <p> (paragraph), <pre> (code block), <note>, <warn> (warning) and <impo> (important) tags all can contain one or more lines of text. Besides the <table> element (which we'll cover in just a bit), these are the only tags that should appear immediately inside a <body> element. Another thing -- these tags should not be stacked -- in other words, don't put a <note> element inside a <p> element. As you might guess, the <pre> element preserves its whitespace exactly, making it well-suited for code excerpts. You can also name the <pre> tag:

Code Listing 2.5: Named <pre>

<pre caption = "Output of uptime">
# <i>uptime</i>
16:50:47 up 164 days,  2:06,  5 users,  load average: 0.23, 0.20, 0.25
</pre>

The <path>, <c> and <e> elements can be used inside any child <body> tag, except for <pre>.

The <path> element is used to mark text that refers to an on-disk file -- either an absolute or relative path, or a simple filename. This element is generally rendered with a monospaced font to offset it from the standard paragraph type.

The <c> element is used to mark up a command or user input. Think of <c> as a way to alert the reader to something that they can type in that will perform some kind of action. For example, all the XML tags displayed in this document are enclosed in a <c> element because they represent something that the user could type in that is not a path. By using <c> elements, you'll help your readers quickly identify commands that they need to type in. Also, because <c> elements are already offset from regular text, it is rarely necessary to surround user input with double-quotes. For example, don't refer to a "<c>" element like I did in this sentence. Avoiding the use of unnecessary double-quotes makes a document more readable -- and adorable!

<e> is used to apply emphasis to a word or phrase; for example: I really should use semicolons more often. As you can see, this text is offset from the regular paragraph type for emphasis. This helps to give your prose more punch!

We've taken a look at the <mail> tag earlier; it's used to link some text with a particular email address, and takes the form <mail link="[email protected]">Mr. Foo Bar</mail>.

The <uri> tag is used to point to files/locations on the Internet. It has two forms -- the first can be used when you want to have the actual URI displayed in the body text, such as this link to http://www.gentoo.org. To create this link, I typed <uri>http://www.gentoo.org</uri>. The alternate form is when you want to associate a URI with some other text -- for example, the Gentoo Linux website. To create this link, I typed <uri link="http://www.gentoo.org">the Gentoo Linux website</uri>.

Figures

Here's how to insert a figure into a document -- <figure link="mygfx.png" short="my picture" caption="my favorite picture of all time"/>. The link= attribute points to the actual graphic image, the short= attribute specifies a short description (currently used for the image's HTML alt= attribute), and a caption. Not too difficult :) We also support the standard HTML-style <img src="foo.gif"/> tag for adding images without captions, borders, etc.

Tables and lists

Guide supports a simplified table syntax similar to that of HTML. To start a table, use a <table> tag. Start a row with a <tr> tag. However, for inserting actual table data, we don't support the HTML <td> tag; instead, use the <th> if you are inserting a header, and <ti> if you are inserting a normal informational block. You can use a <th> anywhere you can use a <ti> -- there's no requirement that <th> elements appear only in the first row. Currently, these tags don't support any attributes, but some will be added (such as a caption= attribute for <table>) soon.

To create ordered or unordered lists, simply use the HTML-style <ol>, <ul> and <li> tags. List tags should only appear inside a <body>, <ul> or <ol> tag.

Intra-document references

Guide makes it really easy to reference other parts of the document using hyperlinks. You can create a link pointing to Chapter One by typing <uri link="#doc_chap1">Chapter One</uri>. To point to section two of Chapter One, type <uri link="#doc_chap1_sect2">section two of Chapter One</uri>. To refer to figure 3 in chapter 1, type <uri link="doc_chap1_fig3">figure 1.3</uri>. Or, to refer to code listing 2 in chapter 2, type <uri link="doc_chap2_pre2">code listing 2.2</uri>. We'll be adding other auto-link abilities (such as table support) soon.

However, some guides change often and using such "counting" can lead to broken links. In order to cope with this, you can define a name for a <chapter> or <section> by using the id attribute, and then point to that attribute, like this:

Code Listing 2.6: Using the id attribute

<chapter id="foo">
<title>This is foo!</title>
...
<p>
More information can be found in the <uri link="#foo">foo chapter</uri>
</p>

3. Coding Style

Introduction

Since all Gentoo Documentation is a joint effort and several people will most likely change existing documentation, a coding style is needed. A coding style contains two sections. The first one is regarding internal coding - how the xml-tags are placed. The second one is regarding the content - how not to confuse the reader.

Both sections are described next.

Internal Coding Style

Newlines must be placed immediately after every GuideXML-tag (both opening as closing), except for: <version>, <date>, <title>, <th>, <ti>, <li>, <i>, <e>, <uri>, <path>, <b>, <comment>, <codenote>, <mail>.

Blank lines must be placed immediately after every <body> (opening tag only) and before every <chapter>, <p>, <table>, <author> (set), <pre>, <ul>, <ol>, <warn>, <note> and <impo> (opening tags only).

Word-wrapping must be applied at 80 characters except inside <pre>. Only when there is no other choice can be deviated from this rule (for instance when a URL exceeds the maximum amount of characters). The editor must then wrap whenever the first whitespace occurs.

Indentation may not be used, except with the XML-constructs of which the parent XML-tags are <tr> (from <table>), <ul>, <ol> and <author>. If indentation is used, it must be two spaces for each indentation. That means no tabs and not more spaces.

In case word-wrapping happens in <ti>, <th> or <li> constructs, indentation must be used for the content.

An example for indentation is:

Code Listing 3.1: Indentation Example

<table>
<tr>
  <th>Foo</th>
  <th>Bar</th>
</tr>
<tr>
  <ti>This is an example for indentation.</ti>
  <ti>
    In case text cannot be shown within an 80-character wide line, you
    must use indentation if the parent tag allows it.
  </ti>
</tr>
</table>

<ul>
  <li>First option</li>
  <li>Second option</li>
</ul>

Attributes may not have spaces in between the attribute, the "=" mark, and the attribute value. As an example:

Code Listing 3.2: Attributes

Wrong  :     <pre caption = "Attributes">
Correct:     <pre caption="Attributes">

External Coding Style

Inside tables (<table>) and listings (<ul> and <ol>), periods (".") should not be used unless multiple sentences are used. In that case, every sentence should end with a period (or other reading marks).

Every sentence, including those inside tables and listings, should start with a capital letter.

Code Listing 3.3: Periods and capital letters

<ul>
  <li>No period</li>
  <li>With period. Multiple sentences, remember?</li>
</ul>

Code Listings should always have a caption.

Try to use <uri> with the link attribute as much as possible. In other words, the Gentoo Website is preferred over http://www.gentoo.org.

When you comment something inside a <pre> construct, only use <codenote> if the content is a C or C++ code snippet. Otherwise, use <comment> and parantheses. Also place the comment before the subject of the comment.

Code Listing 3.4: Comment example

(Substitute "john" with your user name)
# id john

4. Handbook Format

Guide vs Book

For high-volume documentation, such as the Installation Instructions, a broader format was needed. We designed a GuideXML-compatible enhancement that allows us to write modular and multi-page documentation.

Main File

The first change is the need for a "master" document. This document contains no real content, but links to the individual documentation modules. The syntaxis doesn't differ much from GuideXML:

Code Listing 4.1: Example book usage

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE book SYSTEM "/dtd/book.dtd">

<book link="example.xml">
<title>Example Book Usage</title>

<author...>
  ...
</author>

<abstract>
  ...
</abstract>

<!-- The content of this document is licensed under the CC-BY-SA license -->
<!-- See http://creativecommons.org/licenses/by-sa/2.0 -->
<license/>

<version>...</version>
<date>...</date>

So far no real differences (except for the <book> instead of <guide> tag). Instead of starting with the individual <chapter>'s, you define a <part>, which is the equivalent of a separate part in a book:

Code Listing 4.2: Defining a part

<part>
<title>Part One</title>
<abstract>
  ...
</abstract>

(Defining the several chapters)
</part>

Each part is accompanied by a <title> and an <abstract> which gives a small introduction to the part.

Inside each part, you define the individual <chapter>'s. Each chapter must be a separate document. As a result it is no surprise that a special tag (<include>) is added to allow including the separate document.

Code Listing 4.3: Defining a chapter

<chapter>
<title>Chapter One</title>
<abstract>
  This is a small explanation on chapter one.
</abstract>

  <include href="path/to/chapter-one.xml"/>

</chapter>

Designing the Individual Chapters

The content of an individual chapter is structured as follows:

Code Listing 4.4: Chapter Syntax

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE sections SYSTEM "/dtd/book.dtd">

<!--  The content of this document is licensed under the CC-BY-SA license -->
<!--  See http://creativecommons.org/licenses/by-sa/2.0 -->

<sections>

(Define the several <section> and <subsection>)

</sections>

Inside each chapter you can define <section>'s (equivalent of <chapter> in a Guide) and <subsection>'s (equivalent of <section> in a Guide).

5. Resources

Start writing

Guide has been specially designed to be "lean and mean" so that developers can spend more time writing documentation and less time learning the actual XML syntax. Hopefully, this will allow developers who aren't unusually "doc-savvy" to start writing quality Gentoo Linux documentation. If you'd like to help (or have any questions about guide), please post a message to the gentoo-doc mailing list stating what you'd like to tackle. Have fun!

The contents of this document are licensed under the Creative Commons - Attribution / Share Alike license.

Updated August 12, 2004

Daniel Robbins
Author

John P. Davis
Author

Jorge Paulo
Editor

Sven Vermeulen
Editor

Summary: This guide shows you how to compose web documentation using the new lightweight Gentoo GuideXML syntax. This syntax is the official format for Gentoo Linux documentation, and this document itself was created using GuideXML. This guide assumes a basic working knowledge of XML and HTML.