287,874 research outputs found
Model Checking Timed Recursive CTL
We introduce Timed Recursive CTL, a merger of two extensions of the well-known branching-time logic CTL: Timed CTL is interpreted over real-time systems like timed automata; Recursive CTL introduces a powerful recursion operator which takes the expressiveness of this logic CTL well beyond that of regular properties. The result is an expressive logic for real-time properties. We show that its model checking problem is decidable over timed automata, namely 2-EXPTIME-complete
Success Strategies of Small Business Owners
In the United States, 20% of newly established small businesses, including small
businesses in the life insurance industry, fail within 2 years, and over 50% of them fail during the first 5 years. The purpose of this multiple case study was to identify and explore the strategies that life insurance brokerage owners use to sustain business operations beyond 5 years. Porter\u27s 5 forces model served as the conceptual framework for exploring this subject matter. Owners of 3 separate small life insurance brokerage firms in Texas, who sustained their businesses beyond 5 years, participated in semistructured interviews. A secondary source of data was relevant company documents. Methodological triangulation and member checking assured the reliability and validity of the interpretations. Through thematic analysis and supporting software, 5 themes emerged: exceptional customer service, relationship-building, efficient promotional strategies, regular training of salespersons, and hiring the right employees. The application of the findings of the study could contribute to positive social change by reducing unemployment and thereby catalyzing an economic environment supporting employees, families, and communities
Beyond Language Equivalence on Visibly Pushdown Automata
We study (bi)simulation-like preorder/equivalence checking on the class of
visibly pushdown automata and its natural subclasses visibly BPA (Basic Process
Algebra) and visibly one-counter automata. We describe generic methods for
proving complexity upper and lower bounds for a number of studied preorders and
equivalences like simulation, completed simulation, ready simulation, 2-nested
simulation preorders/equivalences and bisimulation equivalence. Our main
results are that all the mentioned equivalences and preorders are
EXPTIME-complete on visibly pushdown automata, PSPACE-complete on visibly
one-counter automata and P-complete on visibly BPA. Our PSPACE lower bound for
visibly one-counter automata improves also the previously known DP-hardness
results for ordinary one-counter automata and one-counter nets. Finally, we
study regularity checking problems for visibly pushdown automata and show that
they can be decided in polynomial time.Comment: Final version of paper, accepted by LMC
Finite Model Finding for Parameterized Verification
In this paper we investigate to which extent a very simple and natural
"reachability as deducibility" approach, originated in the research in formal
methods in security, is applicable to the automated verification of large
classes of infinite state and parameterized systems. The approach is based on
modeling the reachability between (parameterized) states as deducibility
between suitable encodings of states by formulas of first-order predicate
logic. The verification of a safety property is reduced to a pure logical
problem of finding a countermodel for a first-order formula. The later task is
delegated then to the generic automated finite model building procedures. In
this paper we first establish the relative completeness of the finite
countermodel finding method (FCM) for a class of parameterized linear arrays of
finite automata. The method is shown to be at least as powerful as known
methods based on monotonic abstraction and symbolic backward reachability.
Further, we extend the relative completeness of the approach and show that it
can solve all safety verification problems which can be solved by the
traditional regular model checking.Comment: 17 pages, slightly different version of the paper is submitted to
TACAS 201
Forward Analysis and Model Checking for Trace Bounded WSTS
We investigate a subclass of well-structured transition systems (WSTS), the
bounded---in the sense of Ginsburg and Spanier (Trans. AMS 1964)---complete
deterministic ones, which we claim provide an adequate basis for the study of
forward analyses as developed by Finkel and Goubault-Larrecq (Logic. Meth.
Comput. Sci. 2012). Indeed, we prove that, unlike other conditions considered
previously for the termination of forward analysis, boundedness is decidable.
Boundedness turns out to be a valuable restriction for WSTS verification, as we
show that it further allows to decide all -regular properties on the
set of infinite traces of the system
On computing fixpoints in well-structured regular model checking, with applications to lossy channel systems
We prove a general finite convergence theorem for "upward-guarded" fixpoint
expressions over a well-quasi-ordered set. This has immediate applications in
regular model checking of well-structured systems, where a main issue is the
eventual convergence of fixpoint computations. In particular, we are able to
directly obtain several new decidability results on lossy channel systems.Comment: 16 page
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