Explaining Missing Query Results in Natural Language

We propose in this paper a novel approach for explaining query non-answers in Natural Language within the context of Natural Language Interfaces to Databases (NLIDBs). Such interfaces allow non-expert users to pose queries over an underlying database; our goal is to further allow users to ask why some results that they have expected to see, are missing from the output. In a nutshell, our approach is to “marry" NLIDBs with an existing model for explaining missing query results by pinpointing the last query operator that is “responsible" for the missing result. We observe that one can often trace the parts of the original NL question that correspond to these operators. This paves the way for intuitive explanations of the non-answers, that are based on highlighting the relevant parts of the question. Our architecture is generic and is not coupled with a specific NLIDB, and our solution yields clear explanations in interactive speed.