Local model checking and protocol analysis

We consider the model checking problem for Hybrid Logic. Known algorithms so far are global in the sense that they compute, inductively, in every step the set of all worlds of a Kripke structure that satisfy a subformula of the input. Hence, they always exploit the entire structure. Local model checking tries to avoid this by only traversing necessary parts of the input in order to establish or refute the satisfaction relation between a given world and a formula. We present a framework for local model checking of Hybrid Logic based on games. We show that these games are simple reachability games for ordinary Hybrid Logic and weak Buchi games for Hybrid Logic with operators interpreted over the transitive closure of the accessibility relation of the underlying Kripke frame, and show how to solve these games thus solving the local model checking problem. Since the first-order part of Hybrid Logic is inherently hard to localise in model checking, we give examples, in the end, of how global model checkers can be optimised in certain special cases using well-established techniques like fixpoint approximations and divide-and-conquer algorithms.

We provide a model-checking technique for a logic for true concurrency, whose formulae predicate about events in computations and their causal dependencies. The logic, that represents the logical counterpart of history-preserving bisimilarity, is naturally interpreted over event structures. It includes minimal and maximal fixpoint operators and thus it can express properties of infinite computations. Global algorithms are not convenient in this setting, since the event structure associated with a system is typically infinite (even if the system is finite state), a fact that makes also the decidability of model-checking non-trivial. Focusing on the alternation free fragment of the logic, along the lines of some classical work for the modal mu-calculus, we propose a local model-checking algorithm. The algorithm is given in the form of a tableau system, for which, over a class of event structures satisfying a suitable regularity condition, we prove termination, soundness and completeness.

Model-checking is a popular technique for verifying finitestate concurrent systems, whose behaviour can be modeled using Labeled Transition Systems (Ltss). In this paper, we study the model-checking problem for the modal µ-calculus on acyclic Ltss. This has various applications of practical interest such as trace analysis, log information auditing, run-time monitoring, etc. We show that on acyclic Ltss, the full µ-calculus has the same expressive power as its alternation-free fragment. We also present two new local model-checking algorithms based upon a translation to boolean equation systems. The first algorithm handles μ-calculus formulas. with alternation depth ad(ϕ)≥ 2 and has time complexity O(∣ϕ∣)2⋅(∣S∣+∣T∣)) and space complexity O(∣ϕ∣2⋅∣S∣), where ∣S∣ and ∣T∣ are the number of states and transitions of the acyclic Lts and ∣ϕ∣ is the number of operators in ϕ The second algorithm handles formulas ϕ with alternation depth ad(ϕ)= 1 and has time complexity O(∣ϕ∣⋅(∣S∣+∣T∣)) and space complexity O(∣ϕ∣⋅∣S∣).KeywordsModel CheckTemporal LogicSpace ComplexityConjunctive Normal FormPropositional VariableThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

In this paper we show that observation equivalence on CCS processes preserves temporal properties (drawn from a very general temporal logic encompassing standard linear and branching time logics). Moreover, relative to a progress requirement, we show that CCS processes are live. But it is also very important to be able to verify that a process has or lacks a temporal property. In Section 3 we briefly discuss the idea of local model checking, checking that a particular finitary process has a property. Finally in Section 4 we exhibit a correct model checker for a sublogic, the linear time mu-calculus, of the general temporal logic.

We present a proof system for determining satisfaction between processes in a fairly general process algebra and assertions of the modal mu-calculus. The proof system is compositional in the structure of processes. It extends earlier work on compositional reasoning within the modal mu-calculus and combines it with techniques from work on local model checking. The proof system is sound for all processes and complete for a class of finite-state processes.

Global Navigation Satellite System fast precise positioning can be achieved with accurate ionospheric corrections computed from an adequate number of GNSS stations in a local region. In low-latitude regions, the presence of electron density gradients over short distances can lead to outliers in the map of ionospheric corrections and decrease its accuracy. In this study, we explored outlier detection in ionospheric correction mapping through statistical residuals during a four-month test in 2021. Our findings indicate that the residuals of the local ionospheric model conform to the Laplace distribution. To determine outliers, we use an empirical rule for the Laplace distribution, setting thresholds at μ ± 3b, μ ± 3.5b, and μ ± 5.8b for data retention rates of 95%, 97%, and 99.7%, respectively. Here, μ represents the location parameter, which corresponds to the median of data, and b is the scale parameter, calculated as the medium absolute deviation. We found that while removing outliers can improve model accuracy, it may result in unavailable prediction due to a lack of data in a spare network. For example, applying a μ ± 3.5b threshold for outlier removal led to approximately 2.5% of recording time having no ionospheric corrections map in low-latitude regions, however, the local model has the potential to improve its mean accuracy by up to 50% for both low and mid-latitudes. Therefore, choosing the appropriate percentile threshold depends on the network configuration and the desired accuracy. Removing erroneous satellite data to improve ionospheric accuracy brings positive impacts on precise positioning.

Systems biology requires accurate models of protein complexes, including physical interactions that assemble and regulate these molecular machines. Yeast two-hybrid (Y2H) and affinity-purification/mass-spectrometry (AP-MS) technologies measure different protein-protein relationships, and issues of completeness, sensitivity and specificity fuel debate over which is best for high-throughput 'interactome' data collection. Static graphs currently used to model Y2H and AP-MS data neglect dynamic and spatial aspects of macromolecular complexes and pleiotropic protein function. We apply the local modeling methodology proposed by Scholtens and Gentleman (2004) to two publicly available datasets and demonstrate its uses, interpretation and limitations. Specifically, we use this technology to address four major issues pertaining to protein-protein networks. (1) We motivate the need to move from static global interactome graphs to local protein complex models. (2) We formally show that accurate local interactome models require both Y2H and AP-MS data, even in idealized situations. (3) We briefly discuss experimental design issues and how bait selection affects interpretability of results. (4) We point to the implications of local modeling for systems biology including functional annotation, new complex prediction, pathway interactivity and coordination with gene-expression data. The local modeling algorithm and all protein complex estimates reported here can be found in the R package apComplex, available at http://www.bioconductor.org dscholtens@northwestern.edu http://daisy.prevmed.northwestern.edu/~denise/pubs/LocalModeling

Mechanical theorem proving and model checking are the two main methods of formal verification, each with its own strengths and weaknesses. While mechanical theorem proving is more general, it requires intensive human guidance. Model checking is automatic, but is applicable to a more restricted class of problems. It is appealing to combine these two methods in order to take advantage of their different strengths. Prior research in this direction has focused on how to decompose a verification problem into parts each of which is manageable by one of the two methods. In this paper we explore another possibility: we use mechanical theorem proving to formally verify a meta-theory of model checking. As a case study, we use the mechanical theorem prover HOL to verify the correctness of a partial-order reduction technique for cutting down the amount of state search performed by model checkers. We choose this example for two reasons. First, this reduction technique has been implemented in the protocol analysis tool SPIN to significantly speed up the analysis of many practical protocols; hence its correctness has important practical consequences. Second, the correctness arguments involve nontrivial mathematics, the formalization of which we hope will become the basis of a formal meta-theory of other model-checking algorithms and techniques. Interestingly, our formalization led to a nontrivial generalization of the original informal theory. We discuss the lessons, both encouraging and discouraging, learned from this exercise. In the appendix we highlight the important definitions and theorems from each of our HOL theories. The complete listing of our HOL proof is given in a separate document because of space limitations.

The journey towards realizing real-time AI-driven IoT applications is facing a significant hurdle caused by the limited resources of IoT devices. Particularly for battery-powered edge devices, the decision between performing task inference locally or by offloading to edge servers, all while ensuring timely results and conserving energy, is a critical issue. This problem is further complicated when an edge device houses multiple local inference models. The challenge of effectively allocating inference models to tasks between local models and edge server models under strict time and energy constraints while maximizing overall accuracy is recognized as a strongly NP-hard problem and has not been addressed in the literature. Therefore, in this work we propose MASITO, a novel multi-agent deep reinforcement learning framework designed to address this intricate problem. By dividing the problem into two sub-problems namely task scheduling and edge server selection we propose a cooperative multi-agent system for addressing each sub-problem. MASITO’s design allows for faster training and more robust schedules using cooperative behavior where agents compensate for each other’s sub-optimal actions. Moreover, MASITO dynamically adapts to different network configurations which allows for high-mobility edge computing applications. Experiments on the ImageNet-mini dataset demonstrate the framework’s efficacy, outperforming genetic algorithms (GAs), simulated annealing (SA), and particle swarm optimization (PSO) in scheduling times by providing lower times ranging from 60% up to 90% while maintaining comparable average accuracy in worst-case scenarios and superior accuracy in best-case scenarios.

When some agents want to communicate through a media stream (for example voice or video), the Real Time Protocol (RTP) is used. This protocol does not provide encryption, so it is necessary to use Secure RTP (SRTP) to secure the communication. In order for this to work, the agents need to agree on key material and ZRTP provides them with a procedure to perform this task: it is a key agreement protocol, which relies on a Diffie-Hellman exchange to generate SRTP session parameters, providing confidentiality and protecting against Man-in-the-Middle attacks even without a public key infrastructure or endpoint certificates. This is an analysis of the ZRTP protocol performed with ProVerif, which tests security properties; in order to perform the analysis, the protocol has been modeled in the applied -calculus.

Internet Protocol (IP) and network devices play a major role as internet users in the world are exponentially increasing. There is a requirement for a much larger number of unique IP addresses and network devices for connecting sequentially. IPV 6 has been showing progressive improvement over IPV 4 and implementation of the former is challenging which requires impulsive pre-installation testing techniques. Many of the service qualities are evaluated by the real-time implementation of the different topological networks for transmitting multimedia traffic. This paper works over the real-time experimental analysis of various protocols via a client-server network, configured using wired & wireless networks, and also involves the analysis of optical network performance in the multicast transmission of multimedia data. The simulation results show that using Hyper Text Transfer Protocol (HTTP) has increased the throughput against Real Time Protocol (RTP) and use of optical fiber cable has enhanced the throughput by a considerable rate while compared to ethernet cable.

We propose a model checking scheme for a semantically complete fragment of CTL by combining techniques from constraint logic programming, a restricted form of constructive negation and tabled resolution. Our approach is symbolic in that it encodes and manipulates sets of states using constraints; it supports local model checking using goal-directed computation enhanced by tabulation. The framework is parameterized by the constraint domain and supports any finite constraint domain closed under disjunction, projection and complementation. We show how to encode our fragment of CTL in constraint logic programming; we outline an abstract execution model for the resulting type of programs and provide a preliminary evaluation of the approach.

Traditional real-time control systems are tightly integrated into the industrial processes they govern. Now, however, there is increasing interest in networked control systems. These provide greater flexibility and cost savings by allowing real-time controllers to interact with industrial processes over existing communications networks. New data packet queuing protocols are currently being developed to enable precise real-time control over a network with variable propagation delays. We show how one such protocol was formally modelled using timed automata, and how model checking was used to reveal subtle aspects of the control system's dynamic behaviour.

The formal analysis of security protocols is a prime example of a domain where model checking has been successfully applied. Although security protocols are typically small, analysis by hand is difficult as a protocol should work even when arbitrarily many runs are interleaved and in the presence of an adversary. Specialized model-checking techniques have been developed that address both the problems of unbounded, interleaved runs and a prolific, highly nondeterministic adversary. These techniques have been implemented in model-checking tools that now scale to protocols of realistic size and can be used to aid protocol design and standardization.

This paper presents general techniques for formally modeling, simulating, and model checking real-time resource-sharing protocols in Real-Time Maude. The "scheduling subset" of our techniques has been used to find a previously unknown subtle bug in a state-of-the-art scheduling algorithm. This paper also shows how our general techniques can be instantiated to model and analyze the well known priority inheritance protocol.