9.3.3 XML documents

The parser can operate in two modes: the sgml mode and the xml mode, as defined by the dialect(Dialect) option. HTML is a special case of the SGML mode with a particular DTD. Regardless of this option, if the first line of the document reads as below, the parser is switched automatically to the XML mode.

	<?xml ... ?>

Switching to XML mode implies:

• XML empty elements
  The construct <element attribute ... attribute/> is recognized as an empty element.

• Predefined entities
  The following entities are predefined: < (<), > (>), & (&), ' (') and " (").

• Case sensitivity
  In XML mode, names of tags and attributes are case-sensitive, except for the DTD reserved names (i.e. ELEMENT, etc.).

• Character classes
  In XML mode, underscore (_) and colon (:) are allowed in names.

• White-space handling
  White space mode is set to preserve. In addition, the XML reserved attribute xml:space is honored; it may appear both in the document and the DTD. The remove extension (see space(remove) earlier) is allowed as a value of the xml:space attribute. For example, the DTD statement below ensures that the pre element preserves space, regardless of the default processing mode.

  		<!ATTLIST pre xml:space nmtoken #fixed preserve>