Learning in Goal Oriented Autonomous Systems

This report, prepared for the Computer Science Laboratory at SRI International, covers the development of a Learning component for PAGODA, a modular architecture for goal directed agents that explore an environment without need for constant commands from an operator. Two learning algorithms are presented and our algorithm implementations analyzed. The report highlights the changes made to PAGODA and the development challenges encountered. Additionally, several potential improvements to the PAGODA system are given

Specification and Analysis of Priced Systems in Priced-Timed Maude

This thesis investigates the suitability of extending the rewriting-logic-based Maude framework, in particular Real-Time Maude, to support the formal modeling and analysis of untimed and timed priced systems. The first contribution of this thesis is to define priced and priced-timed rewrite theories, show the soundness of these definitions, and prove that priced-time rewrite theories contain as a proper subset the set of priced-timed automata (PTA). Since all priced systems that I have encountered have been real-time systems, I focus on priced real-time (priced-timed) systems. The second main contribution of the thesis is the development of a tool, Priced-Timed Maude, supporting the specification and analysis of useful subclasses of priced and priced-timed rewrite theories. In particular, Priced-Timed Maude supports the specification of the large and important class of ``flat'' object-oriented priced-timed systems, for which I have developed useful and intuitive specification techniques. This thesis then applies Priced-Timed Maude to three larger systems, two of which can be considered benchmarks for priced-timed systems and are often encountered in the literature, and one which has been inspired by a ``regular'' problem found in optimization literature. I have also modeled and analyzed one of these systems using the only well known formal tool for priced-timed systems that I have found, the PTA tool Uppaal CORA, and have compared the performance of these Priced-Timed Maude and Uppaal CORA specifications. Unsurprisingly, Uppaal CORA outperforms Priced-Timed Maude when analyzing this problem. This is natural, since the PTA model is quite restrictive. On the other hand, Priced-Timed Maude is more general and expressive, and lets us model more complex systems with advanced data types and communication features in an elegant and intuitive style. Furthermore, Priced-Timed Maude supports a wide range of formal analysis methods, including: rewriting for simulation, search for reachability analysis, linear temporal logic model checking, and finding cost- and time-optimal solutions

Automatic proof-search heuristics in the maude invariant analyzer tool

The Invariant Analyzer Tool is an interactive tool that mechanizes an inference system for proving safety properties of concurrent systems, which may be infinite-state or whose set of initial states may be infinite. This paper presents the automatic proof-search heuristics at the core of the Maude Invariant Analyzer Tool, which provide a substantial degree of automation and can automatically discharge many proof obligations without user intervention. These heuristics can take advantage of equationally defined equality predicates and include rewriting, narrowing, and SMT-based proof-search techniques

Towards automatic Maude specifications generation from C functions

In this paper, we aim to contribute to the knowledge about how imperative C functions can be transformed to Maude functional and system modules respectively. Maude is a formal specification language characterized by simplicity, expressivity and good performance. It is a multi-paradigm meta-language based on rewriting logic and equational theories used to specify, simulate and formally verify concurrent and distributed systems. Maude has been used to define the operational semantics of many programming and specification languages. In particular, the addition of this paper is to close the gap between a subset of the C standard language and Maude relying on a transformational approach

Verification and validation of UML and SysML based systems engineering design models

In this thesis, we address the issue of model-based verification and validation of systems engineering design models expressed using UML/SysML. The main objectives are to assess the design from its structural and behavioral perspectives and to enable a qualitative as well as a quantitative appraisal of its conformance with respect to its requirements and a set of desired properties. To this end, we elaborate a heretofore unattempted unified approach composed of three well-established techniques that are model-checking, static analysis, and software engineering metrics. These techniques are synergistically combined so that they yield a comprehensive and enhanced assessment. Furthermore, we propose to extend this approach with performance analysis and probabilistic assessment of SysML activity diagrams. Thus, we devise an algorithm that systematically maps these diagrams into their corresponding probabilistic models encoded using the specification language of the probabilistic symbolic model-checker PRISM. Moreover, we define a first of its kind probabilistic calculus, namely activity calculus, dedicated to capture the essence of SysML activity diagrams and its underlying operational semantics in terms of Markov decision processes. Furthermore, we propose a formal syntax and operational semantics for the input language of PRISM. Finally, we mathematically prove the soundness of our translation algorithm with respect to the devised operational semantics using a simulation preorder defined upon Markov decision processes

Programming and symbolic computation in Maude

[EN] Rewriting logic is both a flexible semantic framework within which widely different concurrent systems can be naturally specified and a logical framework in which widely different logics can be specified. Maude programs are exactly rewrite theories. Maude has also a formal environment of verification tools. Symbolic computation is a powerful technique for reasoning about the correctness of concurrent systems and for increasing the power of formal tools. We present several new symbolic features of Maude that enhance formal reasoning about Maude programs and the effectiveness of formal tools. They include: (i) very general unification modulo user-definable equational theories, and (ii) symbolic reachability analysis of concurrent systems using narrowing. The paper does not focus just on symbolic features: it also describes several other new Maude features, including: (iii) Maude's strategy language for controlling rewriting, and (iv) external objects that allow flexible interaction of Maude object-based concurrent systems with the external world. In particular, meta-interpreters are external objects encapsulating Maude interpreters that can interact with many other objects. To make the paper self-contained and give a reasonably complete language overview, we also review the basic Maude features for equational rewriting and rewriting with rules, Maude programming of concurrent object systems, and reflection. Furthermore, we include many examples illustrating all the Maude notions and features described in the paper.Duran has been partially supported by MINECO/FEDER project TIN2014-52034-R. Escobar has been partially supported by the EU (FEDER) and the MCIU under grant RTI2018-094403-B-C32, by the Spanish Generalitat Valenciana under grant PROMETE0/2019/098, and by the US Air Force Office of Scientific Research under award number FA9550-17-1-0286. MartiOliet and Rubio have been partially supported by MCIU Spanish project TRACES (TIN2015-67522-C3-3-R). Rubio has also been partially supported by a MCIU grant FPU17/02319. Meseguer and Talcott have been partially supported by NRL Grant N00173 -17-1-G002. Talcott has also been partially supported by ONR Grant N00014-15-1-2202.Durán, F.; Eker, S.; Escobar Román, S.; NARCISO MARTÍ OLIET; José Meseguer; Rubén Rubio; Talcott, C. (2020). Programming and symbolic computation in Maude. Journal of Logical and Algebraic Methods in Programming. 110:1-58. https://doi.org/10.1016/j.jlamp.2019.100497S158110Alpuente, M., Escobar, S., Espert, J., & Meseguer, J. (2014). A modular order-sorted equational generalization algorithm. 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Symbolic reachability analysis using narrowing and its application to verification of cryptographic protocols. Higher-Order and Symbolic Computation, 20(1-2), 123-160. doi:10.1007/s10990-007-9000-6C. Olarte, E. Pimentel, C. Rocha, Proving structural properties of sequent systems in rewriting logic, in: [121], 2018, pp. 115–135.Ölveczky, P. C., & Meseguer, J. (2007). Semantics and pragmatics of Real-Time Maude. Higher-Order and Symbolic Computation, 20(1-2), 161-196. doi:10.1007/s10990-007-9001-5Ölveczky, P. C., & Thorvaldsen, S. (2009). Formal modeling, performance estimation, and model checking of wireless sensor network algorithms in Real-Time Maude. Theoretical Computer Science, 410(2-3), 254-280. doi:10.1016/j.tcs.2008.09.022Rocha, C., Meseguer, J., & Muñoz, C. (2017). Rewriting modulo SMT and open system analysis. Journal of Logical and Algebraic Methods in Programming, 86(1), 269-297. doi:10.1016/j.jlamp.2016.10.001Şerbănuţă, T. F., Roşu, G., & Meseguer, J. (2009). 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