Validating xml dtd
extends the set of allowed characters to include all the above, plus the remaining characters in the range U 0001–U 001F.At the same time, however, it restricts the use of C0 and C1 control characters other than U 0009 (Horizontal Tab), U 000A (Line Feed), U 000D (Carriage Return), and U 0085 (Next Line) by requiring them to be written in escaped form (for example U 0001 must be written as or its equivalent).IETF RFC:3023, now superseded by RFC:7303, gave rules for the construction of Internet Media Types for use when sending XML. Further guidelines for the use of XML in a networked context appear in RFC 3470, also known as IETF BCP 70, a document covering many aspects of designing and deploying an XML-based language.The material in this section is based on the XML Specification.There are many other text encodings that predate Unicode, such as ASCII and ISO/IEC 8859; their character repertoires in almost every case are subsets of the Unicode character set.XML allows the use of any of the Unicode-defined encodings, and any other encodings whose characters also appear in Unicode.Disparate systems communicate with each other by exchanging XML messages.The message exchange format is standardised as an XML schema (XSD). XML has come into common use for the interchange of data over the Internet.
XML is widely used in a Services Oriented Architecture (SOA).
The specification places requirements on what an XML processor must do and not do, but the application is outside its scope.
The processor (as the specification calls it) is often referred to colloquially as an XML parser.
In computing, Extensible Markup Language (XML) is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable.
The W3C's XML 1.0 Specification It is a textual data format with strong support via Unicode for different human languages.
XML also provides a mechanism whereby an XML processor can reliably, without any prior knowledge, determine which encoding is being used.