in order to communicate data structures between different computers and possibly different programming languagesxml (extensible markup languagehas become quasi-standard the above list could be represented in xml as howeverthere are usually many different ways to represent the same object in xml for instancea cell-oriented representation of the above list would be emptylist while this looks complicated for simple listit is notit is just bit lengthy xml is flexible enough to represent and communicate very complicated structures in uniform way implementation of lists there are many different implementations possible for listsand which one is best will depend on the primitives offered by the programming language being used the programming language lisp and its derivatesfor instancetake lists as the most important primitive data structure in some other languagesit is more natural to implement