This article presents the main features of XMCDA, a standardised XML proposal to represent objects and data issued from the field of Multiple Criteria Decision Aid (MCDA). Its main objective is to allow different MCDA algorithms to interact and to be easily callable from a software like, e.g., the diviz platform of the Decision Deck project. We present the structure of XMCDA and detail the main underlying data structures via examples speaking for themselves.