14 research outputs found

    Completeness of Tree Automata Completion

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    We consider rewriting of a regular language with a left-linear term rewriting system. We show a completeness theorem on equational tree automata completion stating that, if there exists a regular over-approximation of the set of reachable terms, then equational completion can compute it (or safely under-approximate it). A nice corollary of this theorem is that, if the set of reachable terms is regular, then equational completion can also compute it. This was known to be true for some term rewriting system classes preserving regularity, but was still an open question in the general case. The proof is not constructive because it depends on the regularity of the set of reachable terms, which is undecidable. To carry out those proofs we generalize and improve two results of completion: the Termination and the Upper-Bound theorems. Those theoretical results provide an algorithmic way to safely explore regular approximations with completion. This has been implemented in Timbuk and used to verify safety properties, automatically and efficiently, on first-order and higher-order functional programs

    Defining an approximation to formally verify cryptographic protocols

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    Electronic forms of communication are abundant in todays world, and much emphasis is placed on these methods of communication in every day life. In order to guarantee the secrecy and authenticity of information exchanged, it is vital to formally verify the cryptographic protocols used in these forms of communications. This verification does, however, present many challenges. The systems to verify are infinite, with an infinite number of sessions and of p articipants. As if this was not enough, there is also a reactive element to deal with: th e intruder. The intruder will attack the protocol to achieve his goal: usurping identity, stealing confidential information, etc. His behavior is unpredictable! This thesis describes a method of verification based 011 the verification of systems by approximation. Starting from an initial configuration of the network, an overapproximation of the set of messages exchanged is automatically computed. Secrecy and authentication properties can then be checked on the approximated system. Starting from an existing semi-automatic proof method developed by Genet and Klay, an automatic solution is developed. Starting from an existing semi-automatic proof method developed by Genet and Klay, an automatic solution is developed. This thesis defines a particular approximation function that can be generated automatically and that guarantees that the computation of the approximated system terminates. Th e verification by approximation only tells if properties are verified. When the verification fails no conclusion can be drawn on the property. Thus, this thesis also shows how the approximation technique can easily be combined with another verification technique to combine the strengths of both approaches. Finally, the tool developed to validate these developments and the results of cryptographic protocol verifications carried out in the course of this research are included

    Certifying Confluence of Almost Orthogonal CTRSs via Exact Tree Automata Completion

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    Suzuki et al. showed that properly oriented, right-stable, orthogonal, and oriented conditional term rewrite systems with extra variables in right-hand sides are confluent. We present our Isabelle/HOL formalization of this result, including two generalizations. On the one hand, we relax proper orientedness and orthogonality to extended proper orientedness and almost orthogonality modulo infeasibility, as suggested by Suzuki et al. On the other hand, we further loosen the requirements of the latter, enabling more powerful methods for proving infeasibility of conditional critical pairs. Furthermore, we formalized a construction by Jacquemard that employs exact tree automata completion for non-reachability analysis and apply it to certify infeasibility of conditional critical pairs. Combining these two results and extending the conditional confluence checker ConCon accordingly, we are able to automatically prove and certify confluence of an important class of conditional term rewrite systems

    Electronic collaborative mass customization as a competitive strategy – Exploring the key success factors

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    OBJECTIVES OF THE STUDY Electronic collaborative mass customization (ECMC) – online customer-centered product design – is an emerging discipline. The objective of the research is to examine ECMC as a competitive strategy through the identification of key success factors that have received inadequate attention previously. More specifically, the aim is to introduce a new framework for value co-creation. METHODOLOGY The data was collected through netnography and themed interviews. With regard to primary data, six (6) Finnish B2C companies’ marketing managers were interviewed in order to obtain a strategic perspective to the phenomenon in question. Moreover, in order to produce triangulation and emphasize customer-centrism, netnography was employed as a secondary method. The collected data was analyzed via theory-bound approach. FINDINGS Based on data analysis, several conclusions and implications were contrived. From the results, it becomes evident that practitioners need to carefully analyze and implement four central elements – systemic (interface, logistics), organizational (culture, resources), customer (experience, commitment), and competitive understanding (offering, promotion) – in order to provide superior customer value and obtain competitive advantage through ECMC. With regard to academics, it is suggested that future research continues the investigation of this new form of competition from different foundations and perspectives
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