Binary Information Press
XML datasets may contain slight variations of data values, especially for numerical values caused by data measurement, data precision, heterogeneous data sources, etc. But human beings may want Functional Dependencies (FDs) can be satisfied in these data items as they only contain very slight variations for the same data item. Traditional definitions of FD in relational databases and XML cannot deal with such situation as they are too "Precise" or "Strict". This paper proposes a new concept of XML FD based on constraint-tree model to deal with such difficult situation.