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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.
Specialised information types
Specialised information types provide a topic architecture that closely matches the structure of your content.
Limits on specialisation
DITA specialisations must conform with immutable rules contained within the DITA specification.

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.
- Working with topics
- Specialised information types
  Specialised information types provide a topic architecture that closely matches the structure of your content.
  - Types of specialisation
    Structural specialisation is used to design completely new information types. Domain specialisation is used to modify the design of semantic elements within an information type.
  - Official specialisations
    Some specialised information types have been developed by the same standards body that is responsible for the DITA standard itself.
  - To specialise or not to specialise
    Specialisation has pros and cons. It adds technical complexity, but can provide better and more appropriate information structures. Specialisation should be carefully planned.
  - Limits on specialisation
    DITA specialisations must conform with immutable rules contained within the DITA specification.
- 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.

Limits on specialisation

DITA specialisations must conform with immutable rules contained within the DITA specification.

Specialisation is not an open-slather, no-rules process. It is a formal, defined process with limitations.

The main requirements of specialisation are:

You cannot make your specialised DITA less restrictive than the DITA base content model.
- You cannot make a mandatory element optional, and you cannot make a mandatory attribute optional.
- You cannot allow elements in positions that are not allowed by the base content model.
You cannot add new element-specific attributes. You can only create new global attributes (or attributes of elements in the base content model.