  In the distributed and dynamic framework of the Web, data quality is a big
challenge. The Linked Open Data (LOD) provides an enormous amount of data, the
quality of which is difficult to control. Quality is intrinsically a matter of
usage, so consumers need ways to specify quality rules that make sense for
their use, in order to get only data conforming to these rules. We propose a
user-side query framework equipped with a checker of constraints and confidence
levels on data resulting from LOD providers\' query evaluations. We detail its
theoretical foundations and we provide experimental results showing that the
check additional cost is reasonable and that integrating the constraints in the
queries further improves it significantly.
