The　concept　of　functional　dependency　plays　a　foundational　role　in　relational　databases　where　it　is　used　in　integrity　enforcement　and　database　design.　Similarly,　functional　dependencies　in　XML　(XFDs)　will　play　a　centric　role　in　providing　richer　data　semantic　information　and　normalizing　XML　data.　In　this　paper,　we　present　a　new　approach　for　defining　XFDs　on　XML　Schema.　While　showing　how　to　extend　XML　Schema,　we　analyze　the　expressive　power　of　our　XFDs.　We　focus　on　supporting　complex　value　(e.g.　list,　set)　in　our　proposal.　The　satisfaction　of　XFDs　in　an　XML　document　is　defined　in　terms　of　the　value　equality.　The　checking　algorithm　for　our　proposal　is　given.　Finally,　we　discuss　the　advantages　of　our　XFDs　over　other　previous　work.