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 <course>...<title>....</title></course> Improper nesting <course>...<title>....</course></title> 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-6th Edition 23.8 @Silberschatz,Korth and SudarshanDatabase System Concepts - 6 23.8 ©Silberschatz, Korth and Sudarshan th Edition 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  <course> … <title> …. </title> </course> Improper nesting  <course> … <title> …. </course> </title> 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