<contrib>§convert4to5, proofreading</contrib></author>
<author><personname>Dick Hamilton</personname>
<email>rlhamilton@frii.com</email>
- <contrib>§changes-removed, proofreading</contrib></author>
+ <contrib>§changes-removed, customization, proofreading</contrib></author>
</authorgroup>
+<pubdate>2006-04-04</pubdate>
<pubdate>2006-03-01</pubdate>
<pubdate>2005-12-28</pubdate>
<pubdate>2005-10-27</pubdate>
</section>
<section xml:id="customizations">
-<title>Customizing DocBook V5.0</title>
+ <title>Customizing DocBook V5.0</title>
+ <!--
+ ** RNG schema organization
+ ** Removing attributes
+ ** Adding new attributes
+ ** Changing permitted content of attribute
+ ** Removing elements
+ ** Adding new elements
+ ** Customizing content models
+ ** Naming and versioning of DocBook customizations
+ -->
+
+ <para>
+ It's much easier to customize DocBook V5.0 than it was to
+ customize earlier releases. This is partly because RELAX NG
+ provides better support for modifications than DTDs and partly
+ because the DocBook schema is designed to take full advantage
+ of the capabilities RELAX NG provides.
+ This section describes the organization of the RELAX NG schema for
+ DocBook, methods and examples for adding, removing, and modifying elements
+ and attributes, and conventions for naming and versioning
+ DocBook customizations.
+ It assumes some familiarity with RELAX NG. If you are unfamiliar
+ with RELAX NG, you can find a tutorial introduction in
+ <citation>RNCTUT</citation>.
+ </para>
+ <section xml:id="relaxngorg">
+ <title>DocBook RELAX NG schema organization</title>
+ <para>
+ The DocBook RELAX NG schema is highly modular, using named
+ patterns extensively. Every element, attribute, attribute
+ list, and enumeration has its own named pattern. In addition,
+ there are named patterns for logical combinations of elements
+ and attributes. These named patterns provide <quote>hooks</quote>
+ into the schema that allow you to do a wide range of customization
+ by simply redefining one or more of the named patterns.
+ </para>
+ <para>
+ An important design characteristic of the schema is that
+ duplication is minimized. This is done through the use of
+ named patterns for common groupings that can be re-used.
+ For example, the <tag>imagedata</tag> and <tag>videodata</tag>
+ elements each have an <tag class="attribute">align</tag> attribute
+ that takes the same set of enumerated values. Rather than
+ repeating those values, a single pattern,
+ <varname>db.halign.enumeration</varname> is referenced by
+ the <varname>db.videodata.align.enumeration</varname>
+ and <varname>db.imagedata.align.enumeration</varname> patterns,
+ which are in turn referenced by the
+ <varname>db.videodata.align.attribute</varname>
+ and <varname>db.imagedata.align.attribute</varname> patterns.
+ While this may seem like overkill, it allows a customizer to modify
+ the allowed enumerations for these two attributes separately or together,
+ or to completely re-define the allowed content of either or both,
+ by redefining one or more of these named patterns.
+ </para>
+ <section xml:id="patternnames"><title>Pattern Names</title>
+ <para>
+ Because named patterns are used extensively, the RELAX NG schema uses
+ several naming conventions. These are:
+ <itemizedlist spacing="compact">
+ <listitem>
+ <para>
+ Names have two or more parts, separated dots <quote>.</quote>
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ The first part of each name is the prefix <quote>db</quote>
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Each element has a named pattern in the form
+ <varname>db.<replaceable>elementname</replaceable></varname>.
+ Elements that have different content models in different
+ contexts will also have patterns in the form
+ <varname>db.<replaceable>context.elementname</replaceable></varname>. For example, <varname>db.figure.info</varname>
+ defines the content model for the <tag>info</tag> element
+ when it appears as a child of the <tag>figure</tag> element.
+ <replaceable>Context</replaceable> may have several parts.
+ For example, <varname>db.cals.entrytbl.thead</varname>.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Most attributes have a named pattern in the form
+ <varname>db.<replaceable>attributename</replaceable>.attribute</varname>.
+ Attributes that have different content models in different
+ contexts will also have patterns in the form
+ <varname>db.<replaceable>context.attributename</replaceable>.attribute</varname>.
+ For example,
+ <varname>db.olink.localinfo.attribute</varname> defines the content
+ model of the <tag class="attribute">localinfo</tag> attribute when
+ it appears in <tag>olink</tag>.
+ There are a few attributes that do not have individual named
+ patterns. For example, the effectivity attributes are grouped
+ into <varname>db.effectivity.attributes</varname> and not identified
+ separately.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Each element has a named pattern for its attribute list in
+ the form
+ <varname>db.<replaceable>elementname</replaceable>.attlist</varname>
+
+ that defines the list of attributes for that element.
+ Elements that have different attribute lists in different
+ contexts will also have patterns in the form
+ <varname>db.<replaceable>context.elementname</replaceable>.attlist</varname>
+ For example, <varname>db.html.table.attlist</varname> defines
+ the attribute list for the html <tag condition="nolink">table</tag> element and
+ <varname>db.cals.table.attlist</varname> defines the attribute
+ list for a cals <tag condition="nolink">table</tag> element.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Each attribute that has enumerated values has a
+ named pattern in the form
+ <varname>db.<replaceable>[context.]attributename</replaceable>.enumeration</varname>.
+ If the enumeration for a particular attribute depends on
+ context, optional context is provided.
+ For example,
+ <varname>db.verbatim.continuation.enumeration</varname> defines
+ the enumeration values for the
+ <tag class="attribute">continuation</tag> attribute that is used
+ in verbatim contexts like <tag>screen</tag>.
+ Unlike elements and attributes, there is not necessarily a
+ named pattern for enumerated attributes outside their context.
+ For example, there is no <varname>db.class.enumeration</varname>
+ because the <tag class="attribute">class</tag> attribute has
+ a broad and non-intersecting range of uses.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ There are several different groupings of elements and attributes.
+ Here are the major ones:
+ <variablelist spacing="compact">
+ <varlistentry>
+ <term>inlines</term>
+ <listitem>
+ <para>
+ Combinations of inline elements, for example,
+ <varname>db.error.inlines</varname>, which contains
+ <varname>db.errorcode</varname>,
+ <varname>db.errortext</varname>, etc.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>blocks</term>
+ <listitem>
+ <para>
+ Combinations of block elements, for example,
+ <varname>db.verbatim.blocks</varname>, which contains
+ <varname>db.programlisting</varname>,
+ <varname>db.screen</varname>, etc.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>attributes</term>
+ <listitem>
+ <para>
+ Combinations of attributes, for example,
+ <varname>db.effectivity.attributes</varname>,
+ which contains the attributes
+ <tag class="attribute">arch</tag>,
+ <tag class="attribute">condition</tag>,
+ <tag class="attribute">conformance</tag>, etc.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>components</term>
+ <listitem>
+ <para>
+ High level components of the schema, for example,
+ <varname>db.navigation.components</varname>, which contains
+ <varname>db.glossary</varname>,
+ <varname>db.bibliography</varname>,
+ <varname>db.index</varname>, and
+ <varname>db.toc</varname>, and is used inside the
+ content model for <tag>chapter</tag>, <tag>appendix</tag>,
+ and <tag>preface</tag>.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>contentmodel</term>
+ <listitem>
+ <para>
+ Shared content models, for example,
+ <varname>db.admonition.contentmodel</varname>, which contains
+ the content model for <tag>tip</tag>, <tag>warning</tag>,
+ <tag>note</tag>, etc.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+ <para>
+ There are a couple of other groupings designed to minimize
+ duplication, but these are the most important.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ </section>
+</section>
+<section xml:id="customconsiderations">
+ <title>General customization considerations</title>
+ <para>
+ Creating a customized schema is similar to
+ creating a customization layer for XSL. The schema customization
+ layer is a new RELAX NG schema that defines your changes and
+ includes the standard docbook schema. You then validate using
+ the schema customization as your schema.
+ </para>
+ <para>
+ <xref linkend="ex-empty" xrefstyle="select: label"/> is an empty
+ RELAX NG customization that does nothing
+ except define the name spaces and include the standard DocBook schema.
+ The <tag class="attribute">href</tag> attribute of the
+ <tag condition="nolink">include</tag> element points to
+ the location of the standard DocBook V5.0 schema.
+ All of the examples are given in both RNG and RNC form.
+<example xml:id="ex-empty"><title>Empty customization file</title>
+<para>RNG</para>
+<programlisting language="rng"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
+<grammar xmlns:db="http://docbook.org/ns/docbook"
+ ns="http://docbook.org/ns/docbook"
+ xmlns="http://relaxng.org/ns/structure/1.0">
+ <include href="docbook.rng"/>
+
+ <!-- redefinitions of named patterns -->
+
+</grammar>]]></programlisting>
+<para>RNC</para>
+<programlisting language="rnc"><![CDATA[namespace db = "http://docbook.org/ns/docbook"
+
+include "docbook.rnc" inherit = db
+# redefinitions of named patterns]]></programlisting>
+</example>
+ </para>
+</section>
+ <section xml:id="cust-elements">
+ <title>Elements</title>
+ <section xml:id="cust-add-elements">
+ <title>Adding elements</title>
+ <para>
+ Adding an element typically takes two definitions.
+ The first defines the new element and
+ its content model, and the second adds the
+ new element into the schema. We'll show two examples.
+ </para>
+ <para>
+ <xref linkend="ex-add-element-1" xrefstyle="select: label"/>
+ adds a new element,
+ <tag condition="nolink">person</tag>, with the same
+ content model as <tag>author</tag>. The new element will be
+ allowed to appear wherever <tag>author</tag> can appear.
+ </para>
+ <para>
+ The <varname>db.author</varname> pattern is copied
+ and renamed <varname>dbx.person</varname>, defining
+ a new element called <tag condition="nolink">person</tag>.
+ Then, the <varname>db.author</varname> pattern is redefined
+ to be a choice of the current value or <varname>dbx.person</varname>.
+ The <tag class="attribute">combine</tag> attribute tells
+ RELAX NG to combine this pattern with the existing named
+ pattern. In this case, the value
+ of the <tag class="attribute">combine</tag> attribute is
+ <quote>choice</quote>, which tells the parser that either
+ the original pattern or this new pattern is a valid match.
+ </para>
+<example xml:id="ex-add-element-1"><title>Adding a new element by duplicating an existing one</title>
+<para>RNG</para>
+<programlisting language="rng"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
+<grammar xmlns:db="http://docbook.org/ns/docbook"
+ ns="http://docbook.org/ns/docbook"
+ xmlns="http://relaxng.org/ns/structure/1.0">
+ <include href="docbook.rng"/>
+ <!-- define the new element -->
+ <define name="dbx.person">
+ <element name="person">
+ <ref name="db.author.attlist"/>
+ <ref name="db.credit.contentmodel"/>
+ </element>
+ </define>
+ <!-- redefine the db.author pattern to allow db.person in
+ the same places as db.author -->
+ <define name="db.author" combine="choice">
+ <ref name="dbx.person"/>
+ </define>
+</grammar>]]></programlisting>
+<para>RNC</para>
+<programlisting language="rnc"><![CDATA[default namespace db = "http://docbook.org/ns/docbook"
+
+include "docbook.rnc"
+# define the new element
+dbx.person =
+ element person { db.author.attlist, db.credit.contentmodel }
+# redefine the db.author pattern to allow db.person in
+# the same places as db.author
+db.author |= dbx.person]]></programlisting>
+</example>
+ <para>
+ The preceding method works well when you'd like a new element
+ to be a clone or near-clone of an existing element. It gives
+ you complete control over the content model, but
+ only limited control over where the element is allowed. It
+ works well when you want to allow the element in the same places
+ as an existing element, and for this example that works
+ nicely, since <tag>author</tag> is allowed in four different
+ named patterns, each of which would have had to be redefined to
+ allow <tag condition="nolink">person</tag>.
+ But, if you can't find an existing element that is allowed in
+ exactly the places you need, this method doesn't work as well.
+ </para>
+ <para>
+ <xref linkend="ex-add-element-2" xrefstyle="select: label"/>
+ adds two new elements by combining them into
+ a higher level pattern. In this example, we'll add
+ two new inline elements for writing about assembly language,
+ <tag condition="nolink">register</tag> and
+ <tag condition="nolink">instruction</tag>.
+ We will allow them whereever programming inlines
+ or operating system inlines are allowed.
+ <xref linkend="ex-add-element-2" xrefstyle="select: label"/>
+ defines the two elements, creates a new named pattern
+ (<varname>dbx.asm.inlines</varname>) that contains them, and adds
+ that pattern to <varname>db.programming.inlines</varname> and
+ <varname>db.os.inlines</varname>. Since these two patterns
+ don't have any elements in common, the strategy used in
+ <xref linkend="ex-add-element-1" xrefstyle="select: label"/>
+ would require selecting two different elements to <quote>clone</quote>,
+ which would be messy.
+ </para>
+<example xml:id="ex-add-element-2"><title>Adding new inline elements</title>
+<para>RNG</para>
+<programlisting language="rng"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
+<grammar xmlns:db="http://docbook.org/ns/docbook"
+ ns="http://docbook.org/ns/docbook"
+ xmlns="http://relaxng.org/ns/structure/1.0">
+ <include href="docbook.rng"/>
+ <!-- define the new elements -->
+ <define name="dbx.register">
+ <element name="register">
+ <text/>
+ </element>
+ </define>
+ <define name="dbx.instruction">
+ <element name="instruction">
+ <text/>
+ </element>
+ </define>
+ <!-- create a new pattern that contains the new inlines -->
+ <define name="dbx.asm.inlines">
+ <choice>
+ <ref name="dbx.register"/>
+ <ref name="dbx.instruction"/>
+ </choice>
+ </define>
+ <!-- add the new inlines to programming and os inlines -->
+ <define name="db.programming.inlines" combine="choice">
+ <ref name="dbx.asm.inlines"/>
+ </define>
+ <define name="db.os.inlines" combine="choice">
+ <ref name="dbx.asm.inlines"/>
+ </define>
+</grammar>]]></programlisting>
+<para>RNC</para>
+<programlisting language="rnc"><![CDATA[default namespace db = "http://docbook.org/ns/docbook"
+
+include "docbook.rnc"
+# define the new elements
+dbx.register = element register { text }
+dbx.instruction = element instruction { text }
+# create a new pattern that contains the new inlines
+dbx.asm.inlines = dbx.register | dbx.instruction
+# add the new inlines to programming and os inlines
+db.programming.inlines |= dbx.asm.inlines
+db.os.inlines |= dbx.asm.inlines]]></programlisting>
+</example>
+ </section>
+ <section xml:id="cust-delete-elements">
+ <title>Deleting elements</title>
+ <para>
+ Deleting elements is straightforward, but takes some
+ care and planning. <xref linkend="ex-delete-element"
+ xrefstyle="select: label"/> deletes
+ the <tag>important</tag> admonition element by redefining
+ it with a content model of <varname>notAllowed</varname>.
+ Note that in this example, the redefinition is inside
+ the <tag condition="nolink">include</tag> element.
+ This is required for
+ redefinitions that completely replace an existing pattern.
+ </para>
+ <para>
+ Be careful; If you delete an element that is a required part
+ of another element's content model, you can make it
+ impossible to create a valid document.
+ For example, if you delete the <tag>title</tag>
+ element, you won't be able to validate a <tag>book</tag>
+ because a <tag>book</tag> requires a <tag>title</tag>.
+ </para>
+<example xml:id="ex-delete-element"><title>Deleting an element</title>
+<para>RNG</para>
+<programlisting language="rng"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
+<grammar xmlns:db="http://docbook.org/ns/docbook"
+ ns="http://docbook.org/ns/docbook"
+ xmlns="http://relaxng.org/ns/structure/1.0">
+ <include href="docbook.rng">
+ <!-- redefine important element as notAllowed -->
+ <define name="db.important">
+ <notAllowed/>
+ </define>
+ </include>
+</grammar>]]></programlisting>
+<para>RNC</para>
+<programlisting language="rnc"><![CDATA[namespace db = "http://docbook.org/ns/docbook"
+
+include "docbook.rnc" inherit = db {
+ # redefine important element as notAllowed
+ db.important = notAllowed
+}]]></programlisting>
+</example>
+ </section>
+ <section xml:id="cust-modify-elements">
+ <title>Customizing the content model of existing elements</title>
+ <para>
+ <xref linkend="ex-modify-element" xrefstyle="select: label"/>
+ expands the definition of <tag>author</tag> to include two
+ new elements, <tag condition="nolink">born</tag> and
+ <tag condition="nolink">died</tag>.
+ The <tag>author</tag> element allows two content models,
+ <varname>db.person.author.contentmodel</varname>, which
+ defines an author who is a person, and
+ <varname>db.org.author.contentmodel</varname>, which
+ defines an author that is an organization. We will modify
+ <varname>db.person.author.contentmodel</varname> so that
+ only authors who are persons can have the new elements.
+<example xml:id="ex-modify-element"><title>Modifying the content model of an element</title>
+<para>RNG</para>
+<programlisting language="rng"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
+<grammar xmlns:db="http://docbook.org/ns/docbook"
+ ns="http://docbook.org/ns/docbook"
+ xmlns="http://relaxng.org/ns/structure/1.0">
+ <include href="docbook.rng"/>
+
+ <define name="db.person.author.contentmodel" combine="interleave">
+ <interleave>
+ <optional>
+ <element name="born">
+ <ref name="db.date.contentmodel"/>
+ </element>
+ </optional>
+ <optional>
+ <element name="died">
+ <ref name="db.date.contentmodel"/>
+ </element>
+ </optional>
+ </interleave>
+ </define>
+</grammar>]]></programlisting>
+<para>RNC</para>
+<programlisting language="rnc"><![CDATA[default namespace = "http://docbook.org/ns/docbook"
+namespace db = "http://docbook.org/ns/docbook"
+
+include "docbook.rnc"
+
+db.person.author.contentmodel &=
+ element born { db.date.contentmodel }?
+ & element died { db.date.contentmodel }?]]></programlisting>
+</example>
+ </para>
+ <para>
+ This modification will allow instances like this:
+<programlisting language="rng"><![CDATA[<author>
+ <personname>Babe Ruth</personname>
+ <born>02/06/1895</born>
+ <died>08/16/1948</died>
+</author>]]></programlisting>
+but because we only modified the content model for authors
+who are human, it won't allow an instance like this, which
+uses <varname>db.org.author.contentmodel</varname>:
+<programlisting language="rng"><![CDATA[<!-- INVALID -->
+<author>
+ <orgname>Boston Red Sox</orgname>
+ <died>1919</died>
+ <born>2004</born>
+</author>]]></programlisting>
+ </para>
+ </section>
+ </section>
+ <section xml:id="cust-attributes">
+ <title>Attributes</title>
+ <section xml:id="cust-add-attributes">
+ <title>Adding attributes</title>
+ <para>
+ The simplest way to add an attribute to a single element
+ is to add it to the attlist pattern for that element.
+ <xref linkend="ex-add-attr" xrefstyle="select: label"/>
+ adds the optional attributes <tag class="attribute">born</tag>
+ and <tag class="attribute">died</tag> to the attribute
+ list for <tag>author</tag>. The <varname>db.author.attlist</varname>
+ named pattern is redefined with the
+ <tag class="attribute">combine</tag> attribute set to
+ <quote>interleave</quote>, which interleaves the two new
+ optional attributes with the existing attributes on the list.
+ </para>
+<example xml:id="ex-add-attr"><title>Adding attributes</title>
+<para>RNG</para>
+<programlisting language="rng"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
+<grammar xmlns:db="http://docbook.org/ns/docbook"
+ ns="http://docbook.org/ns/docbook"
+ xmlns="http://relaxng.org/ns/structure/1.0">
+ <include href="docbook.rng"/>
+
+ <define name="db.author.attlist" combine="interleave">
+ <interleave>
+ <optional>
+ <attribute name="born">
+ <ref name="db.date.contentmodel"/>
+ </attribute>
+ </optional>
+ <optional>
+ <attribute name="died">
+ <ref name="db.date.contentmodel"/>
+ </attribute>
+ </optional>
+ </interleave>
+ </define>
+</grammar>]]></programlisting>
+<para>RNC</para>
+<programlisting language="rnc"><![CDATA[namespace db = "http://docbook.org/ns/docbook"
+
+include "docbook.rnc" inherit = db
-<para>TBD</para>
+db.author.attlist &=
+ attribute born { db.date.contentmodel }?
+ & attribute died { db.date.contentmodel }?]]></programlisting>
+</example>
+ <para>
+ Unlike
+ <xref linkend="ex-modify-element" xrefstyle="select: label"/>,
+ <xref linkend="ex-add-attr" xrefstyle="select: label"/> allows
+ the new attributes to appear on any <tag>author</tag>
+ element, not just those using the person content model.
+ </para>
+ <para>
+ <xref linkend="ex-add-attr-2" xrefstyle="select: label"/> shows
+ how you could limit the use of these attributes to authors who
+ are persons. In this example, the new attributes are interleaved
+ with the <varname>db.person.author.contentmodel</varname>.
+ The only difference between this example and
+ <xref linkend="ex-modify-element" xrefstyle="select: label"/> is
+ that the added patterns are identified as attributes rather than
+ elements. This shows some of the flexibility of RELAX NG, which
+ treats attributes and elements very consistently.
+<example xml:id="ex-add-attr-2"><title>Adding attributes; alternate method</title>
+<para>RNG</para>
+<programlisting language="rng"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
+<grammar xmlns:db="http://docbook.org/ns/docbook"
+ ns="http://docbook.org/ns/docbook"
+ xmlns="http://relaxng.org/ns/structure/1.0">
+ <include href="docbook.rng"/>
+ <!-- redefinitions of named patterns -->
+ <define name="db.person.author.contentmodel" combine="interleave">
+ <interleave>
+ <optional>
+ <attribute name="born">
+ <ref name="db.date.contentmodel"/>
+ </attribute>
+ </optional>
+ <optional>
+ <attribute name="died">
+ <ref name="db.date.contentmodel"/>
+ </attribute>
+ </optional>
+ </interleave>
+ </define>
+</grammar>]]></programlisting>
+<para>RNC</para>
+<programlisting language="rnc"><![CDATA[namespace db = "http://docbook.org/ns/docbook"
+
+include "docbook.rnc" inherit = db
+# redefinitions of named patterns
+db.person.author.contentmodel &=
+ attribute born { db.date.contentmodel }?
+ & attribute died { db.date.contentmodel }?]]></programlisting>
+</example>
+There is one difference in the treatment of attributes and elements
+that is worth noting. By the XML 1.0 definition, the relative order
+of attributes is not significant. Therefore, the
+<tag condition="nolink">interleave</tag> block is not required for
+attributes, though it does no harm.
+ </para>
+ </section>
+ <section xml:id="cust-delete-attributes">
+ <title>Deleting attributes</title>
+ <para>
+ Deleting an attribute is similar to deleting an element,
+ except that you use the RELAX NG <varname>empty</varname>
+ pattern rather than <varname>notAllowed</varname>.
+ <xref linkend="ex-delete-attr" xrefstyle="select: label"/>
+ deletes the linking attributes, which are collected in the
+ <varname>db.common.linking.attributes</varname> pattern,
+ by defining that pattern as <varname>empty</varname>.
+ </para>
+<example xml:id="ex-delete-attr"><title>Deleting an attribute</title>
+<para>RNG</para>
+<programlisting language="rng"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
+<grammar xmlns:db="http://docbook.org/ns/docbook"
+ ns="http://docbook.org/ns/docbook"
+ xmlns="http://relaxng.org/ns/structure/1.0">
+ <include href="docbook.rng">
+ <define name="db.common.linking.attributes">
+ <empty/>
+ </define>
+ </include>
+</grammar>]]></programlisting>
+<para>RNC</para>
+<programlisting language="rnc"><![CDATA[namespace db = "http://docbook.org/ns/docbook"
-<!--
-** RNG schema organization
-** Removing attributes
-** Adding new attributes
-** Changing permitted content of attribute
-** Removing elements
-** Adding new elements
-** Customizing content models
-** Naming and versioning of DocBook customizations
--->
+include "docbook.rnc" inherit = db {
+ db.common.linking.attributes = empty
+}]]></programlisting>
+</example>
+ <para>
+ Generally, <varname>empty</varname> is used when deleting
+ attributes and <varname>notAllowed</varname> is used when
+ deleting elements.
+ </para>
+ </section>
+ <section xml:id="cust-modify-attributes">
+ <title>Changing permitted content of attributes</title>
+ <para>
+ <xref linkend="ex-modify-attr" xrefstyle="select: label"/>
+ modifies <varname>db.spacing.enumeration</varname> to
+ add the additional value <quote>large</quote>. Note
+ that to remove a value from an enumeration, you need
+ to redefine the entire enumeration, minus the values
+ you don't need.
+ </para>
+<example xml:id="ex-modify-attr"><title>Deleting an attribute</title>
+<para>RNG</para>
+<programlisting language="rng"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
+<grammar xmlns:db="http://docbook.org/ns/docbook"
+ ns="http://docbook.org/ns/docbook"
+ xmlns="http://relaxng.org/ns/structure/1.0">
+ <include href="docbook.rng"/>
+ <!-- add value to an enumeration -->
+ <define name="db.spacing.enumeration" combine="choice">
+ <value>large</value>
+ </define>
+</grammar>]]></programlisting>
+<para>RNC</para>
+<programlisting language="rnc"><![CDATA[namespace db = "http://docbook.org/ns/docbook"
+
+include "docbook.rnc" inherit = db
+# add value to an enumeration
+db.spacing.enumeration |= "large"]]></programlisting>
+</example>
+ </section>
+ </section>
+ <section xml:id="cust-naming">
+ <title>Naming and versioning DocBook customizations</title>
+ <para>
+ TBD
+ </para>
+ </section>
</section>
</step>
<step>
<para>Create a schema customization in compact syntax—<filename>dbmathml.rnc</filename>:</para>
-<programlisting>namespace html = "http://www.w3.org/1999/xhtml"
+<programlisting language="rnc">namespace html = "http://www.w3.org/1999/xhtml"
namespace mml = "http://www.w3.org/1998/Math/MathML"
namespace db = "http://docbook.org/ns/docbook"
}
}</programlisting>
<para>Or, alternatively, you can use the XML syntax of RELAX NG—<filename>dbmathml.rng</filename>:</para>
-<programlisting><
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