Create specialized topics when you have a restrictive category of topics that you want to keep consistent and that your users want to distinguish from other categories. Create specialized domains when you have a set of elements that you want available across several of your topic types. Be sure to specialize from the correct base: For example, categories of reference topics should specialize <reference>, categories of tasks should specialize <task>, and domain types should always specialize either <topic> or another domain type.

Read more

Read more

The method for extending specialization-aware transforms is described in more detail in the document, Specializing topic types in DITA.

Yes. Many writers have had at least some experience with HTML as a markup language. The base DITA declarations (DTD and XML Schema) incorporate a number of familiar, general HTML element names. Through specialization, these can always be extended into more specific forms. Generally, XSLT-based transformations from well-formed XHTML into DITA provides faster and more reliable migrations from HTML than copy/paste, although a skilled writer might be able to do so for small portions of content.