The project is aimed to develop an XML update language built on top of XQuery by adding on update primitives, which complies with the standard XQuery Update Facility 1.0 requirements. The end product does this in a flexible way, using a software archi- tecture which enables developers to choose among different XQuery engines and various XML Processing APIs in order to achieve the overall optimal performance for queries with different characteristics. This thesis starts with an investigation on existing proposals and implementations for XML updates, and describes the approach for...