An XML document should begin with an XML declaration denoted by <?xml …… ?>. The three possible attributes are:
version: There are currently version 1.0 and version 1.1. Version 1.1 has not been widely implemented. The main changes are to enable the use of line-ending characters used on EBCDIC platforms, and the use of scripts and characters absent from Unicode 3.2. XML 1.1 came out of a desire to support all the world's languages, and is generally not used.
encoding: This specifies the encoding of the document.
standalone: The valid values are ‘yes’ and ‘no’. A standalone XML document is one that tells the XML processor to ignore any DTDs. ‘yes’ indicates that there are no external markup declarations which affect the information passed from the XML processor to the application.