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Syntax and mark-up
Working with mark-up
Element IDs
Most DITA elements have an id attribute, which is used to uniquely identify the element when the element is re-used. In most cases, id attributes are optional, but an exception is the topic's root element, where it is mandatory.

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.
DITA map files
Syntax and mark-up
- Organisation of DITA elements
  Elements in DITA are grouped together into a number of categories for organisational and comprehension purposes.
- Working with mark-up
  - Element IDs
    Most DITA elements have an id attribute, which is used to uniquely identify the element when the element is re-used. In most cases, id attributes are optional, but an exception is the topic's root element, where it is mandatory.
  - Titles
    A title is not the same as a heading. A topic, a figure, a table and a section should each have only one title.
  - Hacks
    Avoid hacking: using mark-up workarounds that either break the DITA language rules or break the semantic integrity.
  - Comments, draft-comment, and required-cleanup elements
    Standard XML comment mark-up, and DITA specific draft-comment and required-cleanup elements, allow authors to leave notes, comments and unfinished edits that will not be included in the output when the document is published.
  - Use of class attribute
    The class attribute is used in specialisation, and should not be set by a DITA author. The class attribute should not be confused with the outputclass attribute.
  - Similar element names
    DITA includes semantic elements that have almost identical names to others, such as keyword and kwd. These similar elements are intended to be used in different authoring scenarios.
  - Controlling the look-and-feel of the output
    If an element with no specific semantic difference needs to be formatted differently in the output, you can apply the outputclass attribute to the appropriate element.
  - Attaching data to content
    Detailed metadata associated with a DITA element can be stored in data elements in the flow of the content.
- Element domains
  Elements in DITA are arranged into domains for organisational purposes and technical reasons.
- Short descriptions
  The short description (or shortdesc) is arguably the most important component of a DITA topic, and is also one of the most difficult elements to write. Short descriptions should be written for every topic.
- Lists
  The purpose of a list is to make it easier for the reader to understand sequences of information and collections of like information. Different types of lists are used for different information structures.
- Paragraphs
  Paragraphs are the basic components of topics. A paragraph (p) element should be a self-contained unit dealing with one idea or point, typically expressed in two or more related sentences. The p element should be used when no other semantically-specific block element is available.
- Procedures and steps
  The purpose of procedural documents is to explain to the reader how to accomplish tasks. The task information type is specifically designed for procedures, with a well-defined structure built around steps.
- Tables
  The purpose of a table is to structure, organise and present factual data that a user will need to look up or reference. There are two general purpose table types in DITA: table and simpletable.
- Phrases
  The semantics of words and phrases in DITA content is expressed through a broad range of phrase elements.
- Special characters and dates
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.

Element IDs

Most DITA elements have an id attribute, which is used to uniquely identify the element when the element is re-used. In most cases, id attributes are optional, but an exception is the topic's root element, where it is mandatory.

The id attribute of elements must be unique in the context of a file, but ideally, should also be unique in the context of a publication. Many authoring tools automatically generate unique identifiers for elements using a GUID. The id attribute is used in referencing, such as cross-references (xref) and content references (conref).

ID attributes in DITA must start with an alphabetical character, and cannot start with a numerical character. The XML rules for ID attributes require them to start with a letter or an underscore (or a colon).

ID attributes are mandatory for the topic root elements (topic, concept, task and reference), but are optional for most other elements.

If you are going to exchange DITA documents with others, you must ensure that the interchanged document set has unique identifiers; this may require the establishment of naming conventions to avoid identifier conflicts.

Example of a generated (GUID) id attribute:

<concept id="concept_F544B5D5759746C2A199A99518FA1EAE">

Examples of manually created id attributes:

<concept id="c9119">

<cite id="cite_chicago_manual_of_style_ed4">