XML DTD

General Principles

Define the purpose of DTDs in relation to XML documents as a limited and simple way to define the structure of a document.

Be comfortable with DTD terminology: element, attribute, entity, etc.

Realise that like XML, which is based on SGML, XML DTDs are based on SGML DTDs.

Know how to put comments in an XML DTD.

Not covered:

• SGML DTDs, when they differ from XML DTDs (no other knowledge of SGML is required)

DOCTYPE definition Define a DTD for an XML document:

• using an internal DOCTYPE declaration
  • using only the subset of DTD constructs allowed in an internal declaration
• using an external DOCTYPE declaration
  • with the SYSTEM identifier
  • with the PUBLIC identifier
• using a text declaration (<?xml encoding="..." ?>)
• using a mixed DOCTYPE declaration (part internal, part external)
  • with references from one to the other as allowed by the specification
  • applying the precedence rules

Elements

Describe the syntax for defining the root element of a document.

Use <!ELEMENT ...> to describe:

• an empty element
• an element containing text but no nested elements
• an element containing nested elements but no text
  • syntax for specifying the order and number of element occurrences
• a mixed element (containing both text and nested elements)

Attributes

Define which attributes are available for an element using <!ATTLIST ...>.

Describe the following attribute types:

• an attribute with a value from a list of possible values
• a character data attribute (CDATA)
• ID attributes
• IDREF / IDREFS attributes
• NMTOKEN / NMTOKENS attributes
• ENTITY / ENTITIES attributes

Indicate the default value:

• a mandatory attribute (REQUIRED)
• an optional attribute (IMPLIED)
• an attribute with a fixed value (FIXED)
• a default value

Not covered:

• the NOTATION attribute type

Parsed Entities

Use the built-in entities to allow the characters <, >, / and & in an XML document.

Defining entities:

• internal entities
• external entities
  • with the SYSTEM identifier
  • with the PUBLIC identifier

Defining parameter entities:

• group attributes into a parameter entity
• include one parameter entity within another
• reference a parameter entity from a DTD

Not covered:

• unparsed entities