212 research outputs found
Model checking coalitional games in shortage resource scenarios
Verification of multi-agents systems (MAS) has been recently studied taking
into account the need of expressing resource bounds. Several logics for
specifying properties of MAS have been presented in quite a variety of
scenarios with bounded resources. In this paper, we study a different
formalism, called Priced Resource-Bounded Alternating-time Temporal Logic
(PRBATL), whose main novelty consists in moving the notion of resources from a
syntactic level (part of the formula) to a semantic one (part of the model).
This allows us to track the evolution of the resource availability along the
computations and provides us with a formalisms capable to model a number of
real-world scenarios. Two relevant aspects are the notion of global
availability of the resources on the market, that are shared by the agents, and
the notion of price of resources, depending on their availability. In a
previous work of ours, an initial step towards this new formalism was
introduced, along with an EXPTIME algorithm for the model checking problem. In
this paper we better analyze the features of the proposed formalism, also in
comparison with previous approaches. The main technical contribution is the
proof of the EXPTIME-hardness of the the model checking problem for PRBATL,
based on a reduction from the acceptance problem for Linearly-Bounded
Alternating Turing Machines. In particular, since the problem has multiple
parameters, we show two fixed-parameter reductions.Comment: In Proceedings GandALF 2013, arXiv:1307.416
On the Expressiveness of Markovian Process Calculi with Durational and Durationless Actions
Several Markovian process calculi have been proposed in the literature, which
differ from each other for various aspects. With regard to the action
representation, we distinguish between integrated-time Markovian process
calculi, in which every action has an exponentially distributed duration
associated with it, and orthogonal-time Markovian process calculi, in which
action execution is separated from time passing. Similar to deterministically
timed process calculi, we show that these two options are not irreconcilable by
exhibiting three mappings from an integrated-time Markovian process calculus to
an orthogonal-time Markovian process calculus that preserve the behavioral
equivalence of process terms under different interpretations of action
execution: eagerness, laziness, and maximal progress. The mappings are limited
to classes of process terms of the integrated-time Markovian process calculus
with restrictions on parallel composition and do not involve the full
capability of the orthogonal-time Markovian process calculus of expressing
nondeterministic choices, thus elucidating the only two important differences
between the two calculi: their synchronization disciplines and their ways of
solving choices
Unitary Noise and the Mermin-GHZ Game
Communication complexity is an area of classical computer science which
studies how much communication is necessary to solve various distributed
computational problems. Quantum information processing can be used to reduce
the amount of communication required to carry out some distributed problems. We
speak of pseudo-telepathy when it is able to completely eliminate the need for
communication. Since it is generally very hard to perfectly implement a quantum
winning strategy for a pseudo-telepathy game, quantum players are almost
certain to make errors even though they use a winning strategy. After
introducing a model for pseudo-telepathy games, we investigate the impact of
erroneously performed unitary transformations on the quantum winning strategy
for the Mermin-GHZ game. The question of how strong the unitary noise can be so
that quantum players would still be better than classical ones is also dealt
with
On Modal {\mu}-Calculus over Finite Graphs with Bounded Strongly Connected Components
For every positive integer k we consider the class SCCk of all finite graphs
whose strongly connected components have size at most k. We show that for every
k, the Modal mu-Calculus fixpoint hierarchy on SCCk collapses to the level
Delta2, but not to Comp(Sigma1,Pi1) (compositions of formulas of level Sigma1
and Pi1). This contrasts with the class of all graphs, where
Delta2=Comp(Sigma1,Pi1)
Model-Checking an Alternating-time Temporal Logic with Knowledge, Imperfect Information, Perfect Recall and Communicating Coalitions
We present a variant of ATL with distributed knowledge operators based on a
synchronous and perfect recall semantics. The coalition modalities in this
logic are based on partial observation of the full history, and incorporate a
form of cooperation between members of the coalition in which agents issue
their actions based on the distributed knowledge, for that coalition, of the
system history. We show that model-checking is decidable for this logic. The
technique utilizes two variants of games with imperfect information and
partially observable objectives, as well as a subset construction for
identifying states whose histories are indistinguishable to the considered
coalition
CTL Model-Checking with Graded Quantifiers
The use of the universal and existential quantifiers with the capability to express the concept of at least k or all but k, for a non-negative integer k, has been thoroughly studied in various kinds of logics. In classical logic there are counting quantifiers, in modal logics graded modalities, in description logics number restrictions.
Recently, the complexity issues related to the decidability of the μ-calculus, when the universal and existential quantifiers are augmented with graded modalities, have been investigated by Kupfermann, Sattler and Vardi. They have shown that this problem is ExpTime-complete.
In this paper we consider another extension of modal logic, the Computational Tree Logic CTL, augmented with graded modalities generalizing standard quantifiers and investigate the complexity issues, with respect to the model-checking problem. We consider a system model represented by a pointed Kripke structure and give an algorithm to solve the model-checking problem running in time O() which is hence tight for the problem (where |Ï•| is the number of temporal and boolean operators and does not include the values occurring in the graded modalities).
In this framework, the graded modalities express the ability to generate a user-defined number of counterexamples (or evidences) to a specification Ï• given in CTL. However these multiple counterexamples can partially overlap, that is they may share some behavior. We have hence investigated the case when all of them are completely disjoint. In this case we prove that the model-checking problem is both NP-hard and coNP-hard and give an algorithm for solving it running in polynomial space. We have thus studied a fragment of this graded-CTL logic, and have proved that the model-checking problem is solvable in polynomial time
How do we remember the past in randomised strategies?
Graph games of infinite length are a natural model for open reactive
processes: one player represents the controller, trying to ensure a given
specification, and the other represents a hostile environment. The evolution of
the system depends on the decisions of both players, supplemented by chance.
In this work, we focus on the notion of randomised strategy. More
specifically, we show that three natural definitions may lead to very different
results: in the most general cases, an almost-surely winning situation may
become almost-surely losing if the player is only allowed to use a weaker
notion of strategy. In more reasonable settings, translations exist, but they
require infinite memory, even in simple cases. Finally, some traditional
problems becomes undecidable for the strongest type of strategies
Frequency of sexually transmitted diseases and main methodological implications
Background. High risk Human Papillomavirus (HR-HPV) persistence is the most important cervical cancer risk factor, while Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), Mycoplasma hominis (MH), Mycoplasma genitalium(MG), Ureaplasma urealyticum (UU) and parvum (UP) are sexually transmitted diseases (STDs) causing infertility, pregnancy complication, lung problems in newborns. Methods. 135 urine, 135 urethral swabs, 553 cervical swabs, 110 seminal fluids and 1440 Thin Prep, were tested with culture methods, Real-Time PCR (RT-PCR) and multiplex SYBR Green PCR-endpoint to detect STDs. PCR- endpoint was performed to detect HPV. Results. Culture methods showed the lowest sensitivity: for MH it was only 24% (compared to RT-PCR). UP/UU were the most frequent pathogens (13% with culture, 29% with PCR-endpoint, 41,67% with RT-PCR). Turn Around Time was respectively: 48h, 6h and 2h. RT-PCR cervical frequencies for CT, MH, MG, UU, UP were: 5.42%, 11.03%, 1.81%, 11.21% and 35.08%. HPV positivity in primary and secondary screening was 17.33% and 51.14%. Highes t positivity age group was: 23-32 years for CT (17%), and 18-27 years for HPV (33%). Conclusions. RT-PCR is more sensitive, faster, less expensive than other molecular tests like PCR-endpoint and microarrays. It allows more efficient laboratory organization: pre-analytical phase is more automated and enable the implementation of further diagnostic tests for pathologies that need rapid identification, such as meningitidis and sepsis, with reduced human and instrumental resource. Regarding STDs screening, it should be performed in women: for CT at least up to 27 years; for HPV between 35-50 years, since persisting HR-HPV infection is responsible of high-grade lesions
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