Set Of Possible Behaviors Research Articles

An Evolutionary Framework for Modelling Unknown Behaviours of Other Agents

Multiagent decision making becomes complicated when a subject agent interacts with other agents who could be either collaborative or competitive in their common environment. Generally the subject agent does not know what exact behaviours other agents will execute in the coming interactions. This occurs even when the agents are collaborative and cannot fully disclose their behaviours due to their privacy concerns. With the purpose of improving prediction of the true behaviours of other agents, conventional approaches often employ either an exhaust list or a guided search to expand the set of possible behaviours of other agents. In this article, we investigate an evolutionary approach guided by prior knowledge about other agents and develop a genetic algorithm based framework to modelling unknown behaviours, which may contain the true behaviours of other agents. We develop a new framework with a multi-population genetic algorithm in a general multiagent decision model - interactive dynamic influence diagrams, which represents how multiple agents optimise their interactive decisions from the viewpoint of individual agents. The new framework also provides an alternative way to solving the decision model. We demonstrate the performance of the proposed methods in two problem domains and provide empirical results in support.

Simulation under Arbitrary Temporal Logic Constraints

Most model checkers provide a useful simulation mode, that allows users to explore the set of possible behaviours by interactively picking at each state which event to execute next. Traditionally this simulation mode cannot take into consideration additional temporal logic constraints, such as arbitrary fairness restrictions, substantially reducing its usability for debugging the modelled system behaviour. Similarly, when a specification is false, even if all its counter-examples combined also form a set of behaviours, most model checkers only present one of them to the user, providing little or no mechanism to explore alternatives. In this paper, we present a simple on-the-fly verification technique to allow the user to explore the behaviours that satisfy an arbitrary temporal logic specification, with an interactive process akin to simulation. This technique enables a unified interface for simulating the modelled system and exploring its counter-examples. The technique is formalised in the framework of state/event linear temporal logic and a proof of concept was implemented in an event-based variant of the Electrum framework.

Evolution of coordinated punishment to enforce cooperation from an unbiased strategy space.

The emergence and maintenance of punishment to protect the commons remains an open puzzle in social and biological sciences. Even in societies where pro-social punishing is common, some individuals seek to cheat the system if they see a chance to do so—and public goods are often maintained in spite of cheaters who do not contribute. We present a model accounting for all possible strategies in a public goods game with punishment. While most models of punishment restrict the set of possible behaviours, excluding seemingly paradoxical anti-social strategies from the start, we show that these strategies can play an important role in explaining large-scale cooperation as observed in human societies. We find that coordinated punishment can emerge from individual interactions, but the stability of the associated institutions is limited owing to anti-social and opportunistic behaviour. In particular, coordinated anti-social punishment can undermine cooperation if individuals cannot condition their behaviour on the existence of institutions that punish. Only when we allow for observability and conditional behaviours do anti-social strategies no longer threaten cooperation. This is due to a stable coexistence of a minority supporting pro-social institutions and those who only cooperate if such institutions are in place. This minority of supporters is enough to guarantee substantial cooperation under a wide range of conditions. Our findings resonate with the empirical observation that public goods are resilient to opportunistic cheaters in large groups of unrelated individuals. They also highlight the importance of letting evolution, and not modellers, decide which strategies matter.

PCSSL: A stochastic extension to MARTE/CCSL for modeling uncertainty in Cyber Physical Systems

• We propose pCCSL-an extension to MARTE/CCSL to model stochastic behavior of CPSs with probabilistic logical clocks. • We propose modeling occupant energy usage model of energy-aware building. • We present the refinement of SysML/MARTE/pCCSL models with pCCSL. • We show how to evaluate and compare energy consumption of various refinements with statistical model checking. Cyber-Physical Systems (CPSs) are networks of heterogeneous embedded systems immersed within a physical environment, thus combining discrete and continuous processes. As for any complex systems, the global system behavior is difficult to predict, in an analytical way, from the individual behaviors of its parts. A global analysis can only be done through a holistic process, via simulation for instance, requiring precise models of the parts and of their interactions. While the subsystems are usually expected to be fully deterministic, their interactions with the uncertain environment can be difficult to characterize precisely. We propose an approach to characterize the environment and its interactions through stochastic properties, while the discrete part remains fully determined. The novelty of our work is that we explore a more standard-based approach relying on SysML/MARTE. CCSL and logical clocks are used to identify synchronization points in the various heterogeneous UML diagrams. A CCSL specification expresses a set of possible behaviors. Refinement is performed by adding new constraints and thus reducing the set of possible behaviors. The classical MARTE/CCSL-based process explores the remaining solutions through simulation by applying a simulation policy. To help exploring the solution state-space, we propose a stochastic extension of CCSL, called pCCSL, to characterize the likelihood of different configurations to occur. Then, we use Statistical Model Checking to explore alternative solutions and drive the refinement process. We illustrate our proposition by modeling an energy-aware building, with different control strategies and occupant energy usage models. We explore the impact on the energy footprint of the different variants and control strategies.

Renaming Global Variables in C Mechanically Proved Correct

Most integrated development environments are shipped with refactoring tools. However, their refactoring operations are often known to be unreliable. As a consequence, developers have to test their code after applying an automatic refactoring. In this article, we consider a refactoring operation (renaming of global variables in C), and we prove that its core implementation preserves the set of possible behaviors of transformed programs. That proof of correctness relies on the operational semantics of C provided by CompCert C in Coq.

Emergence of coexistence and limit cycles in the chemostat model with flocculation for a general class of functional responses

We consider a model of two microbial species in a chemostat competing for a single-resource, involving the flocculation of the most competitive species which is present in two forms: isolated and attached. We first show that the model with one species and a non-monotonic growth rate of isolated bacteria may exhibit bi-stability and allows the appearance of unstable limit cycles through a sub-critical Hopf bifurcations due to the joined effect of inhibition and flocculation. We then show that the model with two species presents an even richer set of possible behaviors: coexistence, bi-stability and occurrence of stable limit cycles through a super-critical Hopf bifurcations. All these features cannot occur in the classical chemostat model, where generically at most one competitor can survive on a single resource.

Worst-case Throughput Analysis for Parametric Rate and Parametric Actor Execution Time Scenario-Aware Dataflow Graphs

Scenario-aware dataflow (SADF) is a prominent tool for modeling and analysis of dynamic embedded dataflow applications. In SADF the application is represented as a finite collection of synchronous dataflow (SDF) graphs, each of which represents one possible application behaviour or scenario. A finite state machine (FSM) specifies the possible orders of scenario occurrences. The SADF model renders the tightest possible performance guarantees, but is limited by its finiteness. This means that from a practical point of view, it can only handle dynamic dataflow applications that are characterized by a reasonably sized set of possible behaviours or scenarios. In this paper we remove this limitation for a class of SADF graphs by means of SADF model parametrization in terms of graph port rates and actor execution times. First, we formally define the semantics of the model relevant for throughput analysis based on (max,+) linear system theory and (max,+) automata. Second, by generalizing some of the existing results, we give the algorithms for worst-case throughput analysis of parametric rate and parametric actor execution time acyclic SADF graphs with a fully connected, possibly infinite state transition system. Third, we demonstrate our approach on a few realistic applications from digital signal processing (DSP) domain mapped onto an embedded multi-processor architecture.

Combining Wireless Neural Recording and Video Capture for the Analysis of Natural Gait.

Neural control of movement is typically studied in constrained environments where there is a reduced set of possible behaviors. This constraint may unintentionally limit the applicability of findings to the generalized case of unconstrained behavior. We hypothesize that examining the unconstrained state across multiple behavioral contexts will lead to new insights into the neural control of movement and help advance the design of neural prosthetic decode algorithms. However, to pursue electrophysiological studies in such a manner requires a more flexible framework for experimentation. We propose that head-mounted neural recording systems with wireless data transmission, combined with markerless computer-vision based motion tracking, will enable new, less constrained experiments. As a proof-of-concept, we recorded and wirelessly transmitted broadband neural data from 32 electrodes in premotor cortex while acquiring single-camera video of a rhesus macaque walking on a treadmill. We demonstrate the ability to extract behavioral kinematics using an automated computer vision algorithm without use of markers and to predict kinematics from the neural data. Together these advances suggest that a new class of "freely moving monkey" experiments should be possible and should help broaden our understanding of the neural control of movement.

An adaptative agent architecture for holonic multi-agent systems

Self-organized multi-agent systems (MAS) are still difficult to engineer, because, to deal with real world problems, a self-organized MAS should exhibit complex adaptive organizations. In this respect the holonic paradigm provides a solution for modelling complex organizational structures. Holons are defined as self-similar entities that are neither parts nor wholes. The organizational structure produced by holons is called a holarchy. A holonic MAS (HMAS) considers agents as holons that are grouped according to holarchies. The goal of this article is to introduce an architecture that allows holons to adapt to their environment. The metaphor is based upon the immune system and considers stimulations/requests as antigens and selected antibodies as reactions/answers. Each antibody is activated by specific antigens and stimulated and/or inhibited by other antibodies. The immune system rewards (respectively penalizes) selected antibodies, which constitutes a good (respectively wrong) answer to a request. This mechanism allows an agent to choose from a set of possible behaviors, the one that seems the best fit for a specific context. In this context, each holon, atomic or composed, encapsulates an immune system in order to select a behavior. For composed holons, each sub-holon is represented by the selected antibody of its immune system. The super-holon's immune system therefore contains one antibody per sub-holon. This recursive architecture corresponds with the recursive nature of the holarchy. This architecture is presented with an example of simulated robot soccer. From experiments under different conditions we show that this architecture has interesting properties.

PARITY RELATIONS FOR LINEAR DYNAMIC SYSTEMS WITH MULTIPLICATIVE UNCERTAINTIES

This paper proposes a methodology for the design of parity relations for dynamical systems with multiplicative uncertainties. Instead of canceling uncertainties following the example of the so-called robust approaches, uncertain parity relations take uncertainties into account as bounded variables. The method is based on the analysis of zonotopes representing set of possible behaviors. The proposed parity relations design method applies to any uncertain linear system assuming that it is regularly observable. It requires very little computation time: this approach comes down to compute and check linear inequalities at each sample time.

Theory of the Impedance of Electron Diffusion and Recombination in a Thin Layer

This paper analyzes the small signal ac impedance of electron diffusion and recombination in a spatially restricted situation with application in systems such as porous TiO2 nanostructured photoelectrodes and intrinsically conducting polymers. It is shown that the diffusion−recombination model with the main types of boundary conditions assumes a finite set of possible behaviors in the frequency domain, which are classified according to relevant physical parameters. There are four possible cases: (i) the impedance of finite diffusion with reflecting boundary, (ii) the impedance of finite diffusion with absorbing boundary, (iii) the impedance of diffusion-reaction in semiinfinite space or Gerischer impedance, and (iv) the impedance that combines Warburg response at high frequency and a reaction arc at low frequency. The generality of the approach is discussed in terms of the spatial distribution of the electrochemical potential or quasi-Fermi level and also in terms of the transmission line representation....

Probabilistic and prioritized models of timed CSP

In this paper we present two languages that are refinements of timed CSP (Davies and Schneider, this volume): a probabilistic language, and a fully deterministic language with a notion of priority. In the first part of the paper we describe the deterministic language and its semantic model. The syntax is based upon that of timed CSP except some of the operators are refined so as to remove all nondeterminism; this produces prioritized operators. The semantics for our language represents a process as the set of possible behaviours for the process, where a behaviour models the priorities for different actions. A number of algebraic laws for our language are given and the model is illustrated with two examples. In the second part of the paper, we extend the language by adding a probabilistic choice operator. We produce a semantic model for our language which gives the probabilities of different behaviours occurring, as well as modelling the relative priorities for events within a behaviour. The model is illustrated with an example of a communications protocol transmitting messages over an unreliable medium.

The composition and validation of heterogeneous control laws

We present a method for creating and validating a nonlinear controller by the composition of heterogeneous local control laws appropriate to different operating regions. Like fuzzy logic control, these methods apply even in the presence of incomplete knowledge of the structure of the system, the boundaries of the operating regions, or even the control action to take. Unlike fuzzy logic control, these methods can be analyzed by a combination of classical and qualitative methods. Each operating region of the system has a classical control law, which provides high-resolution control and can be analyzed by classical methods. Operating regions are defined by fuzzy set membership functions. The global control law is the weighted average of the local control laws, where the weights are provided by the operating region membership functions. A heterogeneous control law can be analyzed, even in the presence of incomplete knowledge, by representing it as a qualitative differential equation and using qualitative simulation to predict the set of possible behaviors of the system. By expressing the desired guarantee as a statement in a modal temporal logic, the validity of the guarantee can be automatically checked against the set of possible behaviors. We demonstrate heterogeneous controllers and our qualitative methods for proving their properties, first for a simple level controller for a water tank, and second for a highly nonlinear chemical reactor.

Verifying networks of processes that communicate via shared variables

An approach to modelling and verification for networks of processes that communicate solely via shared variables is presented. A process or a network is defined by its set of possible behaviours. Each behaviour is an abstraction of an infinite execution sequence of the process. A linear-time temporal logic formalism is introduced for the specification and verification of safety and liveness properties. The specification of a network can be obtained naturally from the specifications of its component processes.

A model and temporal proof system for networks of processes

An approach is presented for modeling networks of processes that communicate exclusively through message passing. A process (or a network) is defined by its set of possible behaviors, where each behavior is an abstraction of an infinite execution sequence of the process. The resulting model is simple and modular and facilitates information hiding. It can describe both synchronous and asynchronous networks. It supports recursively-defined networks and can characterize liveness properties such as progress of inputs and outputs, termination, and deadlock.A sound and complete temporal proof system based on the model is presented. It is compositional — a specification of a network is formed naturally from specifications of its components.