DITA 1.3 Language Reference : Architectural specification: All-inclusive edition : DITA markup : Subject scheme maps and their usage : Examples of subject scheme maps : Example: How hierarchies defined in a subject scheme map affect filtering
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Example: How hierarchies defined in a subject scheme map affect filtering
This scenario demonstrates how a processor evaluates attribute values when it performs conditional processing for an attribute that is bound to a set of controlled values.
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.
<!-- This examples uses @navtitle rather than <navtitle> solely
to conserve space. Best practises for translate include using <navtitle>. -->
<subjectScheme>
<subjectdef keys="os" navtitle="Operating system">
<subjectdef keys="linux" navtitle="Linux">
<subjectdef keys="redhat" navtitle="RedHat Linux"/>
<subjectdef keys="suse" navtitle="SuSE Linux"/>
</subjectdef>
<subjectdef keys="windows" navtitle="Windows"/>
<subjectdef keys="zos" navtitle="z/OS"/>
</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 should 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 for platform values is "include", this is included. If the default for platform values 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 for platform values is "include", this is included. If the default for platform values is "exclude", this is excluded.
If the default for platform values is "include", this is included. If the default for platform values is "exclude", this is excluded.
Parent topic 
Examples of subject scheme maps