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This article lists the character entity references that are valid in HTML and XML documents. A character entity reference refers to the content of a named entity. An entity declaration is created in XML, SGML and HTML documents (before HTML5) by using the <!ENTITY name "value"> syntax in a Document type definition (DTD).
On the opposite, the code point U+0085 is a valid control character in Unicode and ISO/IEC 10646, as well as in XML 1.0 and XML 1.1 documents (in all contexts), and its usage is not discouraged (it is treated as whitespace in many XML contexts, or as a line-break control similar to U+000D and U+000A in preformatted texts in some XML applications).
These special sequences are character references. Character references that are based on the referenced character's UCS or Unicode code point are called numeric character references. In HTML 4 and in all versions of XHTML and XML, the code point can be expressed either as a decimal (base 10) number or as a hexadecimal (base 16) number. The ...
Similarly, the string "I <3 Jörg" could be encoded for inclusion in an XML document as I <3 Jörg. � is not permitted because the null character is one of the control characters excluded from XML, even when using a numeric character reference. [19] An alternative encoding mechanism such as Base64 is needed to represent such characters.
HTML and XML provide ways to reference Unicode characters when the characters themselves either cannot or should not be used. A numeric character reference refers to a character by its Universal Character Set/Unicode code point, and a character entity reference refers to a character by a predefined name. A numeric character reference uses the ...
If the character encoding for a web page is chosen appropriately, then HTML character references are usually only required for markup delimiting characters as mentioned above, and for a few special characters (or none at all if a native Unicode encoding like UTF-8 is used).
For some XML parsing models, none of them (except the five XML entities) are usable. In others, the HTML DTD is parsed (or assumed) and the HTML entities are permissible. But which set of entities? In particular, HTML5 doesn't indicate the DTD to be used (it's implicit, by defined HTML5 behaviour outside the normal XML or SGML parsing models).
The term CDATA, meaning character data, is used for distinct, but related, purposes in the markup languages SGML and XML.The term indicates that a certain portion of the document is general character data, rather than non-character data or character data with a more specific, limited structure.