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Information types and topics
Topics are the building blocks of modular documents, and organising topics by semantic information types is one of the architectural features of DITA.
What is a topic?
A topic in DITA is an independent chunk of information covering a single idea or task, authored as a unit, and stored in its own file. Topics are categorised by information type. DITA's topic-based architecture enables the same topic to be used in different publications.
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.

Introduction
Information types and topics
Topics are the building blocks of modular documents, and organising topics by semantic information types is one of the architectural features of DITA.
- Content models and information types
  A content model is a framework that represents the structure of the information to be stored. In DITA, a content model is implemented as an information type, or topic type.
- Information types
  A fundamental principle of DITA is information typing, which categorises information according to the nature of the content. The three base DITA information types are concept, task and reference.
- What is a topic?
  A topic in DITA is an independent chunk of information covering a single idea or task, authored as a unit, and stored in its own file. Topics are categorised by information type. DITA's topic-based architecture enables the same topic to be used in different publications.
  - 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.
  - Granularity - one file per topic
    DITA topics should be saved as individual files, and the ditabase composite topic should be avoided.
  - Chunking information into topics
    Documents can be broken down into smaller chunks of content that can be treated as modular building blocks. Chunks should be organised into separate topic files.
  - Avoiding chunk structure in topics
    The hierarchy of information chunks, and the sequence that chunks should appear in published collections, should be defined in the ditamap and not through section elements or nested topics.
- Working with topics
- Specialised information types
  Specialised information types provide a topic architecture that closely matches the structure of your content.
- Topic exemplars
DITA map files
Syntax and mark-up
Language and punctuation
Graphics and figures
Cross-referencing
Cross-references are a means of binding individual topics into a coherent and navigable document.
Content re-use
Metadata, conditional processing, and indexing
The DITA documentation process
DITA authoring concepts
Moving from style-based authoring to a structured authoring methodology such as DITA requires a radically different approach to writing.

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.