1,126 research outputs found
Representing Conversations for Scalable Overhearing
Open distributed multi-agent systems are gaining interest in the academic
community and in industry. In such open settings, agents are often coordinated
using standardized agent conversation protocols. The representation of such
protocols (for analysis, validation, monitoring, etc) is an important aspect of
multi-agent applications. Recently, Petri nets have been shown to be an
interesting approach to such representation, and radically different approaches
using Petri nets have been proposed. However, their relative strengths and
weaknesses have not been examined. Moreover, their scalability and suitability
for different tasks have not been addressed. This paper addresses both these
challenges. First, we analyze existing Petri net representations in terms of
their scalability and appropriateness for overhearing, an important task in
monitoring open multi-agent systems. Then, building on the insights gained, we
introduce a novel representation using Colored Petri nets that explicitly
represent legal joint conversation states and messages. This representation
approach offers significant improvements in scalability and is particularly
suitable for overhearing. Furthermore, we show that this new representation
offers a comprehensive coverage of all conversation features of FIPA
conversation standards. We also present a procedure for transforming AUML
conversation protocol diagrams (a standard human-readable representation), to
our Colored Petri net representation
Action-Evolution Petri Nets: a Framework for Modeling and Solving Dynamic Task Assignment Problems
Dynamic task assignment involves assigning arriving tasks to a limited number
of resources in order to minimize the overall cost of the assignments. To
achieve optimal task assignment, it is necessary to model the assignment
problem first. While there exist separate formalisms, specifically Markov
Decision Processes and (Colored) Petri Nets, to model, execute, and solve
different aspects of the problem, there is no integrated modeling technique. To
address this gap, this paper proposes Action-Evolution Petri Nets (A-E PN) as a
framework for modeling and solving dynamic task assignment problems. A-E PN
provides a unified modeling technique that can represent all elements of
dynamic task assignment problems. Moreover, A-E PN models are executable, which
means they can be used to learn close-to-optimal assignment policies through
Reinforcement Learning (RL) without additional modeling effort. To evaluate the
framework, we define a taxonomy of archetypical assignment problems. We show
for three cases that A-E PN can be used to learn close-to-optimal assignment
policies. Our results suggest that A-E PN can be used to model and solve a
broad range of dynamic task assignment problems
Modelling and Simulation of Queuing Models through the concept of Petri Nets
In recent years Petri Nets has been in demand due to its visual depiction. Petri Nets are used as an effective method for portraying synchronization, a concurrency between different system activities. In queuing models Petri networks are used to represent distributed modeling of the system and thus evaluate their performance. By specifying suitable stochastic Petri Nets models, the authors concentrate on representing multi-class queuing systems of various queuing disciplines. The key idea is to define SPN models that simulate a given queue discipline 's behavior with some acceptable random choice. Authors have find system queuing with both a single server and multiple servers with load-dependent service rate. Petri networks in the queuing model have enhanced scalability by combining queuing and modeling power expressiveness of 'petri networks.' Examples of application of SPN models to performance evaluation of multiprocessor systems demonstrate the utility and effectiveness of this modeling method. In this paper, authors have made use of Stochastic Petri nets in queuing models to evaluate the performance of the system
Analysis of Petri Net Models through Stochastic Differential Equations
It is well known, mainly because of the work of Kurtz, that density dependent
Markov chains can be approximated by sets of ordinary differential equations
(ODEs) when their indexing parameter grows very large. This approximation
cannot capture the stochastic nature of the process and, consequently, it can
provide an erroneous view of the behavior of the Markov chain if the indexing
parameter is not sufficiently high. Important phenomena that cannot be revealed
include non-negligible variance and bi-modal population distributions. A
less-known approximation proposed by Kurtz applies stochastic differential
equations (SDEs) and provides information about the stochastic nature of the
process. In this paper we apply and extend this diffusion approximation to
study stochastic Petri nets. We identify a class of nets whose underlying
stochastic process is a density dependent Markov chain whose indexing parameter
is a multiplicative constant which identifies the population level expressed by
the initial marking and we provide means to automatically construct the
associated set of SDEs. Since the diffusion approximation of Kurtz considers
the process only up to the time when it first exits an open interval, we extend
the approximation by a machinery that mimics the behavior of the Markov chain
at the boundary and allows thus to apply the approach to a wider set of
problems. The resulting process is of the jump-diffusion type. We illustrate by
examples that the jump-diffusion approximation which extends to bounded domains
can be much more informative than that based on ODEs as it can provide accurate
quantity distributions even when they are multi-modal and even for relatively
small population levels. Moreover, we show that the method is faster than
simulating the original Markov chain
Development of a conceptual model of adaptive access rights management with using the apparatus of Petri nets
The paper describes the conceptual model of adaptive control of cyber protection
of the informatization object (IO). Petri's Networks were used as a mathematical
device to solve the problem of adaptive control of user access rights. The simulation
model is proposed and the simulation in PIPE v4.3.0 package is performed. The
possibility of automating the procedures for adjusting the user profile to minimize or
neutralize cyber threats in the objects of informatization is shown. The model of
distribution of user tasks in computer networks of IO is proposed. The model, unlike
the existing, is based on the mathematical apparatus of Petri's Networks and contains
variables that allow reducing the power of the state space. Access control method
(ACM) is added. The addenda touched upon aspects of reconciliation of access rights
that are requested by the task and requirements of the security policy and the degree
of consistency of tasks and access to the IO nodes. Adjustment of rules and security
metrics for new tasks or redistributable tasks is described in the notation of Petri nets
Energy Modeling of Wireless Sensor Nodes Based on Petri Nets
Energy minimization is of great importance in wireless sensor networks in extending the battery lifetime. Accurately understanding the energy consumption characteristics of each sensor node is a critical step for the design of energy saving strategies. This paper develops a detailed probabilistic model based on Petri nets to evaluate the energy consumption of a wireless sensor node. The model factors critical components of a sensor node, including processors with emerging energy-saving features, wireless communication components, and an open or closed workload generator. Experimental results show that this model is more flexible and accurate than Markov models. The model provides a useful simulation platform to study energy saving strategies in wireless sensor networks
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