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