The nested structure gives a sequence and hierarchy of topics within a topic collection. In a Web environment you could disassemble this structure into individual topics and preserve the hierarchy in a generated navigation map or table of contents. However, if the Web is the main delivery vehicle, you might want to author the topics as separate documents and then apply several tables of contents to the same collection of topics. Typically, different information types support different kinds of content. For example, a task typically has a set of steps, whereas a reference topic has a set of customary sections, such as syntax, properties, and usage.
Specialization is the process of creating new categories of topics, or information types.
You can define these new types using the existing ones as a base. By creating a specialized topic type for each type of content, the product architect can ensure that each type of topic has the appropriate content. For example, a user could search for xyz only in messages or only in APIs, as well as searching for xyz across reference topics in general. With such specialization, new information types can use generic processing streams for translation, print, and Web publishing. Although a product group can override or extend these processes, they get the full range of existing processes by default, without any extra work or maintenance.