Programming language evolution via source code query languages

Programming languages evolve just like programs. Language features are added and removed, for example when programs using them are shown to be error-prone. When language features are modified, deprecated, removed or even deemed unsuitable for the project at hand, it is necessary to analyse programs to identify occurrences to refactor. Source code query languages in principle provide a good way to perform this analysis by exploring codebases. Such languages are often used to identify code to refactor, bugs to fix or simply to understand a system better. This paper evaluates seven Java source code query languages: Java Tools Language, Browse-By-Query, SOUL, JQuery, .QL, Jackpot and PMD as to their power at expressing queries required by several use cases (such as code idioms to be refactored).