XML　has　become　the　de　facto　standard　for　representing　and　interchanging　data　in　web-based　applications.　The　wide　use　of　XML　has　necessitated　the　XML　document　semantically　richer.　The　integrity　constraints　for　XML　have　been　widely　investigated　over　the　past　few　years,　with　a　focus　on　keys,　foreign　keys,　functional　dependencies　(XFDs),　multivalued　dependencies　(XMVDs)　and　inclusion　dependencies　(XINDs).　XML　Schema　has　the　ability　to　define　identity　constraints,　but　there　seems　to　be　no　consensus　on　how　to　specify　other　constraints.　In　this　paper,　we　give　an　overview　of　previous　work　in　defining　XFDs,　XMVDs　and　XINDs.　Some　significant　problems　for　defining　and　checking　these　constraints　are　discussed.　A　set　of　requirements　for　a　good　definition　and　checking　algorithm　are　proposed.　©　2010　IEEE.