TQL algebra and its implementation

TQL is a query language for semi-structured data. TQL binding mechanism is based upon the ambient logic. This binding mechanism is the key feature of TQL, but its implementation is far from obvious, being based on a logic which includes "difficult" operators such as negation, universal quantification, recursion, and new tree-related operators. In [6] an "implementation model" is presented, here we first extend it with tree operations, hence obtaining an algebra for the full TQL language. Then we shortly describe the evaluation techniques that we exploit in the actual implementation.