Answer-set programming (ASP) is an emerging logic-programming paradigm that strictly separates the description of a problem from its solving methods. Despite its semantic elegance, ASP suffers from a lack of support for program developers. In particular, tools are needed that help engineers in detecting erroneous parts of their programs. Unlike in other areas of logic programming, applying tracing techniques for debugging logic programs under the answer-set semantics seems rather unnatural, since employing imperative solving algorithms would undermine the declarative flavour of ASP. In this paper, we present the system spock, a debugging support tool for answer-set programs making use of ASP itself. The implemented techniques maintain the declarative nature of ASP within the debugging process and are independent of the actual computation of answer sets. 1 General Information Answer-set programming (ASP) [1] has become an important logic-programming paradigm for declarative problem sol...