Example: How hierarchies defined in a subject scheme map affect filtering

Example

This section is non-normative.

A company defines a subject category for "Operating system", with a key set to os. There are sub-categories for Linux, Windows, and z/OS, as well as specific Linux variants: Red Hat Linux and SuSE Linux. The company then binds the values that are enumerated in the "Operating system" category to the @platform attribute:

<subjectScheme>
    <subjectdef keys="os">
        <topicmeta>
            <navtitle>Operating systems</navtitle>
        </topicmeta>
        <subjectdef keys="linux">
            <topicmeta>
                <navtitle>Linux</navtitle>
            </topicmeta>
            <subjectdef keys="redhat">
                <topicmeta>
                    <navtitle>RedHat Linux</navtitle>
                </topicmeta>
            </subjectdef>
            <subjectdef keys="suse">
                <topicmeta>
                    <navtitle>SuSE Linux</navtitle>
                </topicmeta>
            </subjectdef>
        </subjectdef>
        <subjectdef keys="windows">
            <topicmeta>
                <navtitle>Windows</navtitle>
            </topicmeta>
        </subjectdef>
        <subjectdef keys="zos">
            <topicmeta>
                <navtitle>z/OS</navtitle>
            </topicmeta>
        </subjectdef>
    </subjectdef>
    <enumerationdef>
        <attributedef name="platform"/>
        <subjectdef keyref="os"/>
    </enumerationdef>
</subjectScheme>

The enumeration limits valid values for the @platform attribute to the following: linux, redhat, suse, windows, and zos. If any other values are encountered, processors validating against the scheme will issue a warning.

The following table illustrates how filtering and flagging operate when the above map is processed by a processor. The first two columns provide the values specified in the DITAVAL file. The third and fourth columns indicate the results of the filtering or flagging operation.

att="platform" val="linux"	att="platform" val="redhat"	How platform="redhat" is evaluated	How platform="linux" is evaluated
action="exclude"	action="exclude"	Excluded.	Excluded.
	action="include" or action="flag"	Excluded. This is an error condition, because if all linux content is excluded, redhat also is excluded. Applications can recover by generating an error message.	Excluded.
	Unspecified	Excluded, because redhat is a kind of linux, and linux is excluded.	Excluded.
action="include"	action="exclude"	Excluded, because all redhat content is excluded.	Included.
	action="include"	Included.	Included.
	action="flag"	Included and flagged with the redhat flag.	Included.
	Unspecified	Included, because all linux content is included.	Included.
action="flag"	action="exclude"	Excluded, because all redhat content is excluded.	Included and flagged with the linux flag.
	action="include"	Included and flagged with the linux flag, because linux is flagged and redhat is a type of linux.	Included and flagged with the linux flag.
	action="flag"	Included and flagged with the redhat flag, because a flag is available that is specifically for redhat.	Included and flagged with the linux flag.
	Unspecified	Included and flagged with the linux flag, because linux is flagged and redhat is a type of linux	Included and flagged with the linux flag.
Unspecified	action="exclude"	Excluded, because all redhat content is excluded	If the default value for @platform set in the DITAVAL is "include", this is included. If the default value for @platform set in the DITAVAL is "exclude", this is excluded.
	action="include"	Included.	Included, because all redhat content is included, and general Linux content also applies to RedHat
	action="flag"	Included and flagged with the redhat flag.	Included, because all redhat content is included, and general Linux content also applies to RedHat
	Unspecified	If the default value for @platform set in the DITAVAL is "include", this is included. If the default value for @platform set in the DITAVAL is "exclude", this is excluded.	If the default value for @platform set in the DITAVAL is "include", this is included. If the default value for @platform set in the DITAVAL is "exclude", this is excluded.