The XML Document
The XML document or data packet is considered an XML entity. Within the XML document, various tags similar to HTML tags are used to delineate content. These tags represent elements that form a hierarchy. XML has been designed for internationalization so that documents may be represented in different encoding formats. This requires that the case of characters in the document be preserved, so markup in an XML document is case-sensitive.
An XML document creates structure, applies order to data. Structures within an XML document are always named, usually using markup tags. Certain rules apply to the choice of names in XML document creation. Names must begin with a letter, underscore, or colon, and must continue with a sequence ...