In DITA, both “subject scheme specialization” and “topic specialization” are methods for customizing and enhancing content for specific purposes, but they serve different roles and are applied to different parts of the DITA documentation structure. Let’s explore the differences between the two:

Subject Scheme Specialization

Subject scheme specialization refers to customizing the metadata or classification of DITA topics. It involves the creation of custom subject schemes, taxonomies, or classification systems to categorize topics. These schemes are used to add additional information or context to topics, such as keywords, classifications, or categorizations. Subject scheme specialization allows you to organize and classify topics for different purposes, such as search, navigation, and content filtering. It enhances the discoverability and relevance of topics within a documentation set.

Topic Specialization

Topic specialization, on the other hand, focuses on customizing the structure, content, and behavior of individual DITA topics. It allows you to extend or adapt existing DITA topics to meet specific requirements. Topic specialization might involve defining custom elements, attributes, or constraints within a DITA topic to tailor it to a particular context or use case. This specialization is topic-centric and is used to create variations of topics that maintain consistency within a documentation set while accommodating unique content or formatting needs.

Example:

To illustrate the difference, let’s consider an example. Suppose you have a set of DITA topics related to software documentation, and you want to classify them based on different software versions (e.g., v1.0, v2.0, v3.0) and also provide additional keywords for search purposes. You might use subject scheme specialization to create a custom subject scheme that includes version categories and keywords. This helps in organizing and classifying topics.

<subjectScheme>
  <subjectHeadings>
    <subjectHead type="version">v1.0</subjectHead>
    <subjectHead type="version">v2.0</subjectHead>
    <subjectHead type="version">v3.0</subjectHead>
    <subjectHead type="keyword">installation</subjectHead>
    <subjectHead type="keyword">troubleshooting</subjectHead>
    <subjectHead type="keyword">configuration</subjectHead>
  </subjectHeadings>
</subjectScheme>

For topic specialization, you might create a specialized version of a topic that includes content specific to a particular software version, adapting the topic structure, content, or metadata as needed while using the classification defined in the subject scheme.