XML declaration

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An XML declaration is an identifier string at the beginning of the prologue of an XML file.

syntax

 <?xml version="1.0" encoding="UTF-8" standalone="yes" ?>

The part after <?xmltakes on so-called pseudo-attributes . This is data that has the format attribut="wert". For an XML parser , these are technically no real attributes (hence the name). The order of the pseudo-attributes is determined by the specification (1st version, 2nd encoding, 3rd standalone).

The rule [23] of the XML standard defines the following pseudo-attributes:

version="1.0"
defines the version number of the underlying XML specification. The information is mandatory.
encoding="Zeichenkodierung"
determines the coding of the XML file. The specification is optional. If this parameter is omitted, the content must be encoded in either UTF-8 or UTF-16 if the encoding cannot be determined from the context (e.g. an HTTP header ).
standalone="Wert"
Valid values are yesor no.
The specification is optional; if the parameter is standaloneomitted, it is automatically yesor noassumed depending on the following referencing of an external DTD :
  • The attribute value nois assumed or used when the document references an external DTD .
  • The attribute value yesis assumed or used when the document does not reference an external DTD .
  • The attribute value yesis assumed or used when the document contains an internal DTD .
  • The attribute value yesis assumed or used if the document does not use a DTD .
The attribute value nomust always be specified if the document, including the internal DTD, uses external declarations .

Examples of syntactically correct XML declarations: 

 <?xml version="1.0"?>
 <?xml version="1.0" encoding="ISO-8859-1"?>
 <?xml version="1.0" encoding="UTF-16"?>
 <?xml version="1.0" encoding="EUC-JP" standalone="yes" ?>

See also

Individual evidence

  1. ↑ XML Declaration in: Extensible Markup Language (XML) 1.0 (Fifth Edition). Retrieved January 16, 2017 .
  2. ↑ Standalone Document Declaration in: Extensible Markup Language (XML) 1.0 (Fifth Edition). Retrieved January 17, 2017 .