28 research outputs found
Congruence from the Operator's Point of View: Compositionality Requirements on Process Semantics
One of the basic sanity properties of a behavioural semantics is that it
constitutes a congruence with respect to standard process operators. This issue
has been traditionally addressed by the development of rule formats for
transition system specifications that define process algebras. In this paper we
suggest a novel, orthogonal approach. Namely, we focus on a number of process
operators, and for each of them attempt to find the widest possible class of
congruences. To this end, we impose restrictions on sublanguages of
Hennessy-Milner logic, so that a semantics whose modal characterization
satisfies a given criterion is guaranteed to be a congruence with respect to
the operator in question. We investigate action prefix, alternative
composition, two restriction operators, and parallel composition.Comment: In Proceedings SOS 2010, arXiv:1008.190
On the process of rationalisation of public expenditure
Cele niniejszego artykułu to pełne wyjaśnienie pojęcia racjonalizacji wydatków publicznych, ustalenie różnic między racjonalizacją wyborów a racjonalizacją kosztów, a ponadto ustalenie, czy każde działanie oszczędnościowe można określić mianem racjonalizacji wydatków publicznych. Autor w szczególności przeanalizował zwrot racjonalizacji w kontekście języka prawnego, prawniczego, potocznego i ekonomicznego oraz zaprezentował proces racjonalizacji wydatków publicznych.The aim of this paper is presentation of the term rationalisation of public expenditure, determination of the differences between rationalisation of choices and rationalisation of costs, and furthermore establishment whether each saving act equals to the rationalisation of public expenditure. The author has focused in particular on the analysis of the expression – rationalisation in terms of legal, legalese, colloquial and economic language and present the process of public expenditures rationalisation
Zielonka's Recursive Algorithm: dull, weak and solitaire games and tighter bounds
Dull, weak and nested solitaire games are important classes of parity games,
capturing, among others, alternation-free mu-calculus and ECTL* model checking
problems. These classes can be solved in polynomial time using dedicated
algorithms. We investigate the complexity of Zielonka's Recursive algorithm for
solving these special games, showing that the algorithm runs in O(d (n + m)) on
weak games, and, somewhat surprisingly, that it requires exponential time to
solve dull games and (nested) solitaire games. For the latter classes, we
provide a family of games G, allowing us to establish a lower bound of 2^(n/3).
We show that an optimisation of Zielonka's algorithm permits solving games from
all three classes in polynomial time. Moreover, we show that there is a family
of (non-special) games M that permits us to establish a lower bound of 2^(n/3),
improving on the previous lower bound for the algorithm.Comment: In Proceedings GandALF 2013, arXiv:1307.416
Strategy Derivation for Small Progress Measures
Small Progress Measures is one of the most efficient parity game solving
algorithms. The original algorithm provides the full solution (winning regions
and strategies) in
time, and requires a re-run of the algorithm on one of the winning regions. We
provide a novel operational interpretation of progress measures, and modify the
algorithm so that it derives the winning strategies for both players in one
pass. This reduces the upper bound on strategy derivation for SPM to .Comment: polished the tex
Modal Logic and the Approximation Induction Principle
We prove a compactness theorem in the context of Hennessy-Milner logic. It is
used to derive a sufficient condition on modal characterizations for the
Approximation Induction Principle to be sound modulo the corresponding process
equivalence. We show that this condition is necessary when the equivalence in
question is compositional with respect to the projection operators
Expressiveness and Completeness in Abstraction
We study two notions of expressiveness, which have appeared in abstraction
theory for model checking, and find them incomparable in general. In
particular, we show that according to the most widely used notion, the class of
Kripke Modal Transition Systems is strictly less expressive than the class of
Generalised Kripke Modal Transition Systems (a generalised variant of Kripke
Modal Transition Systems equipped with hypertransitions). Furthermore, we
investigate the ability of an abstraction framework to prove a formula with a
finite abstract model, a property known as completeness. We address the issue
of completeness from a general perspective: the way it depends on certain
abstraction parameters, as well as its relationship with expressiveness.Comment: In Proceedings EXPRESS/SOS 2012, arXiv:1208.244
Conformance Relations and Hyperproperties for Doping Detection in Time and Space
We present a novel and generalised notion of doping cleanness for
cyber-physical systems that allows for perturbing the inputs and observing the
perturbed outputs both in the time- and value-domains. We instantiate our
definition using existing notions of conformance for cyber-physical systems. As
a formal basis for monitoring conformance-based cleanness, we develop the
temporal logic HyperSTL*, an extension of Signal Temporal Logics with trace
quantifiers and a freeze operator. We show that our generalised definitions are
essential in a data-driven method for doping detection and apply our
definitions to a case study concerning diesel emission tests
Oink: an Implementation and Evaluation of Modern Parity Game Solvers
Parity games have important practical applications in formal verification and
synthesis, especially to solve the model-checking problem of the modal
mu-calculus. They are also interesting from the theory perspective, as they are
widely believed to admit a polynomial solution, but so far no such algorithm is
known. In recent years, a number of new algorithms and improvements to existing
algorithms have been proposed. We implement a new and easy to extend tool Oink,
which is a high-performance implementation of modern parity game algorithms. We
further present a comprehensive empirical evaluation of modern parity game
algorithms and solvers, both on real world benchmarks and randomly generated
games. Our experiments show that our new tool Oink outperforms the current
state-of-the-art.Comment: Accepted at TACAS 201
Impacts of soil conditions and light availability on natural regeneration of Norway spruce Picea abies (L.) H. Karst. in low-elevation mountain forests
& Key message Natural regeneration of P. abies (L.) H. Karst. may reach high densities in lower mountain elevations. The
highest densities were found in sites with moderate light availability, with low pH, and not near the riverbank. However,
age-height classes differed in the predicted magnitude of response, but were consistent in response directions. Mosses and
understory species typical of coniferous forests were positively correlated with regeneration density.
& Context Norway spruce Picea abies (L.) H. Karst. in Central Europe is at risk under climate change scenarios, particularly in
mountain regions. Little is known about the impact of environmental factors on the natural regeneration of P. abies in lowelevation mountain forests.
& Aims We aimed to assess impacts of distance from the riverbank, soil pH, and light availability on natural P. abies regeneration.
We hypothesized that (1) natural P. abiesregeneration would depend on light availability and soil pH and (2) there are understory
plant species which may indicate the microsites suitable for natural regeneration of P. abies.
& Methods The study was conducted in the Stołowe Mountains National Park (SW Poland, 600–800 m a.s.l.). We established 160
study plots (25 m2
) for natural regeneration, light availability, soil pH, and understory vegetation assessment