MustBlend: Blending Visual Multi-Source Twig Query Formulation and Query Processing in RDBMS

Recently, in [3, 9] a novel XML query processing paradigm was proposed, where instead of processing a visual XML query after its construction, it interleaves query formulation and processing by exploiting the latency offered by the GUI to filter irrelevant matches and prefetch partial query results. A key benefit of this paradigm is significant improvement of the user waiting time (UWT), which refers to the duration between the time a user presses the “Run” icon to the time when the user gets the query results. However, the current state-of-the-art approach that realizes this paradigm suffers from key limitations such as inability to correctly evaluate certain visual query conditions together when necessary, large intermediate results space, and inability to handle visual query modifications, limiting its usage in practical environment. In this paper, we present a RDBMSbased single as well as multi-source XML twig query evaluation algorithm, called MUSTBLEND (MUlti-Source Twig BLENDer), that addresses these limitations. A key practical feature of MUSTBLEND is its portability as it does not employ any special-purpose storage, indexing, and query cost estimation schemes. Experiments on real-world datasets demonstrate its effectiveness and superiority over existing methods based on the traditional paradigm.