45 research outputs found
Path-Based Program Repair
We propose a path-based approach to program repair for imperative programs.
Our repair framework takes as input a faulty program, a logic specification
that is refuted, and a hint where the fault may be located. An iterative
abstraction refinement loop is then used to repair the program: in each
iteration, the faulty program part is re-synthesized considering a symbolic
counterexample, where the control-flow is kept concrete but the data-flow is
symbolic. The appeal of the idea is two-fold: 1) the approach lazily considers
candidate repairs and 2) the repairs are directly derived from the logic
specification. In contrast to prior work, our approach is complete for programs
with finitely many control-flow paths, i.e., the program is repaired if and
only if it can be repaired at the specified fault location. Initial results for
small programs indicate that the approach is useful for debugging programs in
practice.Comment: In Proceedings FESCA 2015, arXiv:1503.0437
Mucosal malignant melanomas in head and neck surgery: a retrospective study of six patients and review of the literature
Introduction: Of all malignant processes of the oral mucosa, 0.5% are malignant melanomas. Because of late diagnosis, pattern of growth, close proximity to the bone (particularly in palatinal localizations), and the correlated infiltration, malignant melanomas have a bad prognosis. Patients and methods: In this retrospective study, six cases of patients with oral mucosal malignant melanoma are evaluated, and a critical review of the literature is presented. The female to male proportion was 1:1 with an average age of 60.2years; all patients were treated between January 1999 and July 2007. A neck dissection was performed on two patients because of clinically positive lymph nodes; one patient received interleukin 2 therapy, and three patients received postoperative radiotherapy. Two male patients died. Conclusions: We recommend biopsy on every growing lesion, pigmented or nonpigmented, for the required diagnosis and, in cases of malignant melanoma, wide excision as a second step. Neck dissections should be performed in patients with clinically positive lymph nodes. Concerning interleukin 2 therapy, further studies should be performed in order to evaluate a routine applicatio
Synthesizing Adaptive Test Strategies from Temporal Logic Specifications
Constructing good test cases is difficult and time-consuming, especially if
the system under test is still under development and its exact behavior is not
yet fixed. We propose a new approach to compute test strategies for reactive
systems from a given temporal logic specification using formal methods. The
computed strategies are guaranteed to reveal certain simple faults in every
realization of the specification and for every behavior of the uncontrollable
part of the system's environment. The proposed approach supports different
assumptions on occurrences of faults (ranging from a single transient fault to
a persistent fault) and by default aims at unveiling the weakest one. Based on
well-established hypotheses from fault-based testing, we argue that such tests
are also sensitive for more complex bugs. Since the specification may not
define the system behavior completely, we use reactive synthesis algorithms
with partial information. The computed strategies are adaptive test strategies
that react to behavior at runtime. We work out the underlying theory of
adaptive test strategy synthesis and present experiments for a safety-critical
component of a real-world satellite system. We demonstrate that our approach
can be applied to industrial specifications and that the synthesized test
strategies are capable of detecting bugs that are hard to detect with random
testing
Design Understanding: From Logic to Specification
We present an outline of the field of Design Understanding and summarize state-of-the-art research in deriving human-understandable knowledge in form of logic properties from an unknown design
Exact Synthesis of LTL Properties from Traces
We present an exact approach to synthesize temporal-logic formulas in linear temporal logic (LTL) from a set of given positive and negative example traces. Our approach uses topology structures, in particular partial DAGs, to partition the search space into small and manageable subproblems. The algorithm then solves each subproblem independently with the aid of an oracle for deciding satisfiability modulo propositional logic. This strategy is capable of achieving a super-linear speedup when parallelized. We have implemented a bounded synthesis approach to find an LTL formula of minimum size using the proposed topology-guided exact synthesis approach. In an experimental evaluation, we show that the proposed approach achieves a 20x runtime improvement over the state-of-the-art approach