Including a build tag footnote with a topic is equivalent to setting the tag to True when compared to the value set in the Help project file. The Help compiler assumes all other build tags to be False for that topic. After setting the value of the buildtag footnotes to True, the Help compiler evaluates the BUILD expression in the [OPTIONS] section of the Help project file.
Note:
All build tags must be declared in the Help project file, regardless of whether the tags are declared conditionally. If the evaluation results in a True state, the Help compiler includes the topic in the build. Otherwise, the Help compiler omits the topic.
The Help compiler includes topics that do not have a build tag footnote in all builds, regardless of the build tag expressions defined in the Help project file. For this reason, you may want to use build tags primarily to exclude specific topics from certain builds. If the Help compiler finds any build tags not declared in the Help project file, it displays an error message.
By allowing conditional exclusion of specific topics, you can create multiple builds using the same topic files. This saves the Help writing team time and also enables you to maintain a higher level of consistency across your product lines.