Incorporating constraints in probabilistic XML
Sara Cohen, Benny Kimelfeld, Yehoshua Sagiv · 2008
Constraints are important not just for maintaining data integrity, but also because they capture natural probabilistic dependencies among data items. A probabilistic XML database (PXDB) is the probability sub-space comprising the instances of a p-document that satisfy a set of constraints. In contrast to existing models that can express probabilistic dependencies, it is shown that query evaluation is tractable in PXDBs. The problems of sampling and determining well-definedness (i.e., whether the above subspace is nonempty) are also tractable. Furthermore, queries and constraints can include the aggregate functions count, max, min and ratio. Finally, this approach can be easily extended to allow a probabilistic interpretation of constraints.