Structure of XML Data Tag:label for a section of data Element:section of data beginning with <tagname>and ending with matching </tagname> Elements must be properly nested Proper nesting <account>...<balance>....</balance></account> Improper nesting <account>...<balance>....</account></balance> Formally:every start tag must have a unique matching end tag, that is in the context of the same parent element. Every document must have a single top-level element Database System Concepts-5th Edition,Aug 22,2005. 10.8 @Silberschatz,Korth and SudarshanDatabase System Concepts - 5 10.8 ©Silberschatz, Korth and Sudarshan th Edition, Aug 22, 2005. Structure of XML Data Tag: label for a section of data Element: section of data beginning with <tagname> and ending with matching </tagname> Elements must be properly nested Proper nesting  <account> … <balance> …. </balance> </account> Improper nesting  <account> … <balance> …. </account> </balance> Formally: every start tag must have a unique matching end tag, that is in the context of the same parent element. Every document must have a single top-level element