How detailed should a topic be?

A DITA topic should be as short as possible, but as long as is necessary to convey its information independently.

The amount of information per topic within a publication is sometimes referred to as topic granularity. A DITA topic should contain just one idea or answer a single question.

In some cases, a topic may be extremely short, as in the following example of an emergency procedure for a jet fighter aircraft.
<task>
<title>Engine failure below 10,000 feet</title>
<taskbody>
 <steps>
  <step><cmd>Eject.</cmd></step>
 </steps>
</taskbody>
</task>

In other cases, a topic describing a very complex procedure, a very complex concept, an extensive glossary, or a lengthy reference table, may be the equivalent of many pages long. For example, a reference topic listing all the makes and models of cars of the 20th century is very lengthy, but still covers just one subject.

A topic should be as short as possible, but long enough to be independent of other topics. In other words, it must make sense on its own in any context.