Subject Scheme

The Subject Scheme Map is a specialized DITA Map that defines allowed attribute values.

Sample project:


The map.ditamap references the Subject Scheme Map subjectScheme.ditamap. The attributes values are mapped with keys and are therefore available in all topics of the map.ditamap.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE map PUBLIC "-//OASIS//DTD DITA Map//EN" "map.dtd">
  <title>Subject Scheme Map Example</title>
  <topicref href="topic.dita"/>
  <mapref href="subjectScheme.ditamap"/>


The subjectScheme.ditamap defines the attribute values. An attribute value is specified using the @keys attribute of a <subjectdef> element. The key is then used to pull and map its children to an attribute. In this case, in the <enumerationdef> element, the attribute values of the os key are binded to the attribute @platform

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE subjectScheme PUBLIC "-//OASIS//DTD DITA Subject Scheme Map//EN" "subjectScheme.dtd"> 
  <!-- The key "os" is the top level attribute value -->
  <subjectdef keys="os" navtitle="Operating system">
    <subjectdef keys="android" navtitle="Android">
      <subjectdef keys="android5" navtitle="Android 5 Lollipop"/>
      <subjectdef keys="android6" navtitle="Android 6 Marshmallow"/>
      <subjectdef keys="android7" navtitle="Android 7 Nougat"/>
    <subjectdef keys="ios" navtitle="iOS">
      <subjectdef keys="ios8" navtitle="iOS 8 Donner"/>
      <subjectdef keys="ios9" navtitle="iOS 9 Eagle"/>
      <subjectdef keys="ios10" navtitle="iOS 10 Whitetail"/>
    <subjectdef keys="windows" navtitle="Windows">
      <subjectdef keys="windows7" navtitle="Windows 7"/>
      <subjectdef keys="windows8" navtitle="Windows 8"/>
      <subjectdef keys="windows10" navtitle="Windows 10"/>
  <!-- The <enumerationdef> element binds the values of the "os" key to the attribute "platform" -->
    <attributedef name="platform"/>
    <subjectdef keyref="os"/>


If the topic.dita is opened in the scope of the map.ditamap map, the values for the @platform attribute are pulled from the Subject Scheme Map.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE topic PUBLIC "-//OASIS//DTD DITA Topic//EN" "topic.dtd">
<topic id="topic">
        <p platform="android7"/>