  Recent findings suggest that Information Retrieval (IR)-based bug
localization techniques do not perform well if the bug report lacks rich
structured information (eg relevant program entity names). Conversely,
excessive structured information (eg stack traces) in the bug report might not
always help the automated localization either. In this paper, we propose a
novel technique--BLIZZARD-- that automatically localizes buggy entities from
project source using appropriate query reformulation and effective information
retrieval. In particular, our technique determines whether there are excessive
program entities or not in a bug report (query), and then applies appropriate
reformulations to the query for bug localization. Experiments using 5,139 bug
reports show that our technique can localize the buggy source documents with
7%--56% higher Hit@10, 6%--62% higher MAP@10 and 6%--62% higher MRR@10 than the
baseline technique. Comparison with the state-of-the-art techniques and their
variants report that our technique can improve 19% in MAP@10 and 20% in MRR@10
over the state-of-the-art, and can improve 59% of the noisy queries and 39% of
the poor queries.
