The DITA design has a unified content reuse mechanism by which an element can replace itself with the content of a like element elsewhere, either in the current topic or in a separate topic that shares the same content models. The distinction between reusable content and reusing content, often a problem for authors trying to use file and text entities, disappears: Any element with an ID, in any DITA topic, is reusable by conref.

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Most information can be broken down into topics (headings and content). However, if your information requires a more seamless flow of information across topic boundaries, don't use this architecture.

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.

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