Trail-directed model checking

HSF-SPIN is a Promela model checker based on heuristic search strategies. It utilizes heuristic estimates in order to direct the search for finding software bugs in concurrent systems. As a consequence, HSF-SPIN is able to find shorter trails than blind depth-first search. This paper contributes an extension to the paradigm of directed model checking to shorten already established unacceptable long error trails. This approach has been implemented in HSF-SPIN. For selected benchmark and industrial communication protocols experimental evidence is given that trail-directed model-checking effectively shortcuts existing witness paths

Improving Spin's partial-order reduction for breadth-first search

We describe an improvement of the partial-order reduction algorithm for breadth-first search which was introduced in Spin version 4.0. Our improvement is based on the algorithm by Alur et al. for symbolic state model checking for local safety properties [1]. The crux of the improvement is an optimization in the context of explicit state model checking of the condition that prevents action ignoring, also known as the cycle proviso. There is an interesting duality between the cycle provisos for the breadth-first search (BFS) and depth first search (DFS) exploration of the state space, which is reflected in the role of the BFS queue and the DFS stack, respectively. The improved version of the algorithm is supported in the current version of Spin and can be shown to perform significantly better than the initial version

Improving Spin's partial-order reduction for breadth-first search

We describe an improvement of the partial-order reduction algorithm for breadth-first search which was introduced in Spin version 4.0. Our improvement is based on the algorithm by Alur et al. for symbolic state model checking for local safety properties [1]. The crux of the improvement is an optimization in the context of explicit state model checking of the condition that prevents action ignoring, also known as the cycle proviso. There is an interesting duality between the cycle provisos for the breadth-first search (BFS) and depth first search (DFS) exploration of the state space, which is reflected in the role of the BFS queue and the DFS stack, respectively. The improved version of the algorithm is supported in the current version of Spin and can be shown to perform significantly better than the initial version

Verification and Validation of Planning Domain Models

The verification and validation of planning domain models is one of the biggest challenges to deploying planning-based automated systems in the real world.The state-of-the-art verification methods of planning domain models are vulnerable to false positives, i.e. counterexamples that are unreachable by sound planners when using the domain under verification during planning tasks. False positives mislead designers into believing correct models are faulty. Consequently, designers needlessly debug correct models to remove these false positives. This process might unnecessarily constrain planning domain models, which can eradicate valid and sometimes required behaviours. Moreover, catching and debugging errors without knowing they are false positives can give verification engineers a false sense of achievement, which might cause them to overlook valid errors.To address this shortfall, the first part of this thesis introduces goal-constrained planning domain model verification, a novel approach that constrains the verification of planning domain models with planning goals to reduce the number of unreachable planning counterexamples. This thesis formally proves the correctness of this method and demonstrates the application of this approach using the model checker Spin and the planner MIPS-XXL. Furthermore, it reports the empirical experiments that validate the feasibility and investigates the performance of the goal-constrained verification approach. The experiments show that not only the goal-constrained verification method is robust against false positive errors, but it also outperforms under-constrained verification tasks in terms of time and memory in some cases.The second part of this thesis investigates the problem of validating the functional equivalence of planning domain models. The need for techniques to validate the functional equivalence of planning domain models has been highlighted in previous research and has applications in model learning, development and extension. Despite the need and importance of proving the functional equivalence of planning domain models, this problem attracted limited research interest.This thesis builds on and extends previous research by proposing a novel approach to validate the functional equivalence of planning domain models. First, this approach employs a planner to remove redundant operators from the given domain models; then, it uses a Satisfiability Modulo Theories (SMT) solver to check if a predicate mapping exists between the two domain models that makes them functionally equivalent. The soundness and completeness of this functional equivalence validation method are formally proven in this thesis.Furthermore, this thesis introduces D-VAL, the first planning domain model automatic validation tool. D-VAL uses the FF planner and the Z3 SMT solver to prove the functional equivalence of planning domain models. Moreover, this thesis demonstrates the feasibility and evaluates the performance of D-VAL against thirteen planning domain models from the International Planning Competition (IPC). Empirical evaluation shows that D-VAL validates the functional equivalence of the most challenging task in less than 43 seconds. These experiments and their results provide a benchmark to evaluate the feasibility and performance of future related work

Education and Training Report. Performance Report, FY 1997

During FY 97, 152 MUREP education and training projects were conducted at OMU institutions. The institutions conducted precollege and bridge programs, education partnerships with other universities and industry, NRTS, teacher training, and graduate and/or PI undergraduate programs. These programs reached a total of 23,748 participants, with the predominant number at the precollege level and achieved major goals of heightening students' interest and awareness of career opportunities in MSET fields, and exposing students to the NASA mission, research and advanced technology through role models, mentors, and participation in research and other educational activities. Also in FY 1997, NASA continued a very meaningful relationship with the Hispanic Association of Colleges students and Universities (HACU) through Proyecto Access, a consortium through which HACU links seven HSI's together to conduct 8-week summer programs. OMU Institutions reported 4,334 high school student in NASA programs and 3,404 of those students selected college preparatory MSET courses. Three hundred and forty-nine (349) graduated from high school, 343 enrolled in college, and 199 selected MSET majors. There were 130 high school graduates (bridge students) in NASA programs, 57 of whom successfully completed their freshman year. There were 307 teachers in teacher programs and 48 teachers received certificates. Of the 389 undergraduate students, 75 received under graduate degrees, and eight students are employed in a NASA-related field

The Laws of Jamaica, 1846-47

Passed in the tenth year of the reign of Queen Victoria. Published under the Direction of the Commissioners appointed by 59 Geo. III. Cap. XXIV.https://ecollections.law.fiu.edu/jamaica/1000/thumbnail.jp

Bowdoin Orient v.133, no.1-25 (2001-2002)

https://digitalcommons.bowdoin.edu/bowdoinorient-2000s/1002/thumbnail.jp