Types for the Ambient Calculus

The ambient calculus is a concurrent calculus where the unifying notion of ambient is used to model many different constructs for distributed and mobile computation. We study a type system that describes several properties of ambient behavior. The type system allows ambients to be partitioned in disjoint sets (groups), according to the intended design of a system, in order to specify both the communication and the mobility behavior of ambients.     

Designing an algorithm for swarm behavior using the concept of Umwelt

In this study, we propose a methodology for designing a swarm behavior. The difficulty in designing the swarm behavior is a gap between the object of evaluation and that of design. The former is the performance of a group, but the latter is the action of each individual. We utilize the concept “Umwelt” in ethology for bridging the gap. The advantage of this concept is that all actions necessary for the swarm behavior can he derived from the purpose of each individual. Using this concept, the swarm behavior can he built into the action algorithm of the individuals. In order to evaluate the proposed method, we construct the swarm algorithm for a search and collection task. Using a computer simulation, we confirmed that the swarm successfully achieved the task with flexibility and parallelism, and also robustness in part. These results support the effectiveness of the proposed methodology.     

Constructing formal rules to verify message communication in distributed systems

This study presents a method to construct formal rules used to run-time verify message passing between clients in distributed systems. Rules construction is achieved in four steps: (1) Visual specification of expected behavior of the sender, receiver, and network in sending and receiving a message, (2) Extraction of properties of sender, receiver, and network from the visual specification, (3) specification of constraints that should govern message passing in distributed systems, and (4) construction of verifier rules from the properties and the constraints. The rules are used to verify actual sender, receiver, and network behavior. Expected behavior of the client (process) is one that to be and the actual one is the behavior should be verified. The rules were applied to verify the behavior of client and servers that communicated with each other in order to compute Fibonacci numbers in parallel and some violations were discovered.     

Concurrent behavior: A construct to specify the external behavior of objects in object databases

We present a linguistic construct to define concurrency control for the objects of an object database. This construct, calledconcurrent behavior, allows to define a concurrency control specification for each object type in the database; in a sense, it can be seen as a type extension. The concurrent behavior is composed by two parts: the first one, calledcommutativity specification, is a set of conditional rules, by which the programmer specifies when two methods do not conflict each other. The second part, the constraint specification, is a set of guarded regular expressions, calledconstraints, by which the programmer defines the allowed sequences of method calls. At each time during an actual execution, a subset of constraints may be active so limiting the external behavior of the object. A constraint becomesactive when its guard is verified, where a guard is composed of the occurrence of some method callm along with the verification of a boolean expression on the object state and the actual parameters ofm. A constraint dies when a string of the language corresponding to the regular expression has been recognized. While the commutativity specification is devoted to specify the way in which the external behavior of an object is influenced by the existence of concurrent transactions in the system, the constraint specification defines the behavior of the object, independently from the transactions. Since the two parts of the concurrent behavior are syntactically distinct and, moreover, each of them consists of a set of independent rules, modularity in specifying the objects is enhanced, with respect to a unique specification. We outline an implementation of the construct, which is based on a look-ahead policy: at each method execution, we foresee the admissible successive behaviors of the object, instead of checking the admission of each request at the time it is actually made.     

SwingStates: adding state machines to Java and the Swing toolkit

This article describes SwingStates, a Java toolkit designed to facilitate the development of graphical user interfaces and bring advanced interaction techniques to the Java platform. SwingStates is based on the use of finite‐state machines specified directly in Java to describe the behavior of interactive systems. State machines can be used to redefine the behavior of existing Swing widgets or, in combination with a new canvas widget that features a rich graphical model, to create brand new widgets. SwingStates also supports arbitrary input devices to implement novel interaction techniques based, for example, on bi‐manual or pressure‐sensitive input. We have used SwingStates in several Master's‐level classes over the past two years and have developed a benchmark approach to evaluate the toolkit in this context. The results demonstrate that SwingStates can be used by non‐expert developers with little training to successfully implement advanced interaction techniques. Copyright © 2007 John Wiley & Sons, Ltd.     

Understanding human behavior from motion imagery

Computer vision is gradually making the transition from image understanding to video understanding. This is due to the enormous success in analyzing sequences of images that has been achieved in recent years. The main shift in the paradigm has been from recognition followed by reconstruction (shape from X) to motion-based recognition. Since most videos are about people, this work has focused on the analysis of human motion. In this paper, I present my perspective on understanding human behavior. Automatically understanding human behavior from motion imagery involves extraction of relevant visual information from a video sequence, representation of that information in a suitable form, and interpretation of visual information for the purpose of recognition and learning about human behavior. Significant progress has been made in human tracking over the last few years. As compared with tracking, not much progress has been made in understanding human behavior, and the issue of representation has largely been ignored. I present my opinion on possible reasons and hurdles for slower progress in understanding human behavior, briefly present our work in tracking, representation, and recognition, and comment on the next steps in all three areas.Published online: 28 August 2003     

On the rate of convergence of the asymptotic expansion for the ergodic distribution of a semi-Markov (s, S) inventory model

A stochastic process is considered that describes the so-called (s, S) inventory model. The asymptotic behavior of the ergodic distribution of the process is investigated. It is established that the ergodic distribution of the process on the interval [s, S] tends to the uniform distribution for sufficiently large values of the parameter β = S − s, and the convergence rate is estimated.     

Application of nonlinear dynamic analysis to the identification and control of nonlinear systems-III. n-Dimensional systems

In two previous publications, the authors have shown that normal form theory, a method used extensively in dynamic analysis, can be applied in the structure identification of nonlinear systems. In particular, normal form theory bridges the gap between structure of a nonlinear, low order polynomial dynamical system and the behavior it is able to predict or represent. This is important because knowing a system's dynamic behavior automatically leads to a simple nonlinear normal form model that can be used for (nonlinear) control. Previously, only two-dimensional normal form models were derived. For this paper, simple, n-dimensional, low order polynomial dynamical models will be derived that can represent a nonlinear system with multiple steady states or a limit cycle in the operating region of interest. Using as a plant the nonisothermal Continuous Stirred Tank Reactor with consecutive reactions (A→B→C), it is shown that identification and control of this three-dimensional system using the aforementioned normal form models is feasible.     

A platform for P2P agent-based collaborative applications

The operational environment can be a valuable source of information about the behavior of software applications and their usage context. Although a single instance of an application has limited evidence of the range of the possible behaviors and situations that might be experienced in the field, the collective knowledge composed by the evidence gathered by the many instances of a same application running in several diverse user environments (eg, a browser) might be an invaluable source of information. This information can be exploited by applications able to autonomously analyze how they behave in the field and adjust their behavior accordingly. Augmenting applications with the capability to collaborate and directly share information about their behavior is challenging because it requires the definition of a fully decentralized and dependable networked infrastructure whose nodes are the user machines. The nodes of the infrastructure must be collaborative, to share information, and autonomous, to exploit the available information to change their behavior, for instance, to better accommodate the needs of the users to prevent known problems. This paper describes the initial results that we obtained with the design and the development of an infrastructure that can enable the execution of collaborative scenarios in a fully decentralized way. Our idea is to combine the agent-based paradigm, which is well suited to design collaborative and autonomous nodes, and the peer-to-peer paradigm, which is well suited to design distributed and dynamic network infrastructures. To demonstrate our idea, we augmented the popular JADE agent-based platform with a software layer that supports both the creation of a fully decentralized peer-to-peer network of JADE platforms and the execution of services within that network, thus enabling JADE multiagent systems (MASs) to behave as peer-to-peer networks. The resulting platform can be used to study the design of collaborative applications running in the field.     

Analyzing the statistical features of CIXL2 crossover offspring

We cannot deny the effort that the scientific community is devoting to the explanation of the features of the crossover operator of real-coded genetic algorithms and its effect over the evolutive process. This paper is another step in that direction, we analyze the behavior of the Confidence Interval Based Crossover using L₂ Norm (CIXL2). This crossover is based on the learning of the statistical features of localization and dispersion of the best individuals of the population. The crossover obtains, by means of a L₂ norm, the estimators of the parameters of localization and dispersion of the distributions of the fittest individuals. From this estimation three virtual parents are created using the localization parameter and the lower and upper bounds of the bilateral confidence intervals of the gene values of the best individuals of the population. This paper studies the statistical features of the offspring generated by this crossover and corroborates this study showing the behavior of the crossover in a set of test functions.     

Pushdown module checking

Model checking is a useful method to verify automatically the correctness of a system with respect to a desired behavior, by checking whether a mathematical model of the system satisfies a formal specification of this behavior. Many systems of interest are open, in the sense that their behavior depends on the interaction with their environment. The model checking problem for finite-state open systems (called module checking) has been intensively studied in the literature. In this paper, we focus on open pushdown systems and we study the related model-checking problem (pushdown module checking, for short) with respect to properties expressed by CTL and CTL ^* formulas. We show that pushdown module checking against CTL (resp., CTL ^*) is 2Exptime-complete (resp., 3Exptime-complete). Moreover, we prove that for a fixed CTL or CTL ^* formula, the problem is Exptime-complete.     

A Clustered-Based Categorization of Millennials in their Technology Behavior

There is an increasing interest for millennials; however, to date, millennials’ segmentations regarding their technology behavior are scarce. This study addresses the following questions: “Are there segments within this generation group regarding their digital technology behavior?”. And if so: “Are there variances in the way that millennial segments use digital technology?”; and further: “What are the main differences among millennial segments regarding their technology behavior?”.

Data from a sample of 707 millennials were analyzed through principal components and cluster analysis. Then, millennials’ segments were profiled using a multivariate analysis of variance (MANOVA) analysis. Findings revealed that not every millennial has the same technology use and behavior. Moreover, there are five clustered-based segments of millennials regarding their technology behavior: technology devotees, technology spectators, circumspects, technology adverse users, and productivity enhancers. This study contributes with a detailed perspective of how different millennial segments use digital technology.     

Towards modeling user behavior in interactions mediated through an automated bidirectional speech translation system

This paper addresses modeling user behavior in interactions between two people who do not share a common spoken language and communicate with the aid of an automated bidirectional speech translation system. These interaction settings are complex. The translation machine attempts to bridge the language gap by mediating the verbal communication, noting however that the technology may not be always perfect. In a step toward understanding user behavior in this mediated communication scenario, usability data from doctor–patient dialogs involving a two way English–Persian speech translation system are analyzed. We specifically consider user behavior in light of potential uncertainty in the communication between the interlocutors. We analyze the Retry (Repeat and Rephrase) versus Accept behaviors in the mediated verbal channel and as a result identify three user types – Accommodating, Normal and Picky, and propose a dynamic Bayesian network model of user behavior. To validate the model, we performed offline and online experiments. The experimental results using offline data show that correct user type is clearly identified as a user keeps his/her consistent behavior in a given interaction condition. In the online experiment, agent feedback was presented to users according to the user types. We show high user satisfaction and interaction efficiency in the analysis of user interview, video data, questionnaire and log data.     

Construction of C-space roadmaps from local sensory data. What should the sensors look for?

This paper presents an incremental navigation strategy for general articulated robots:the robot may start with no a priori information about its environment, and is guaranteed either to find the goal if it is reachable or halt. The strategy, termed theincremental roadmap algorithm, constructs a roadmap based on on-line distance data which is encoded as a repulsive potential field. The incremental behavior is achieved with two novel abstract sensors: thecritical-point detector and thepassage-point detector. The detectors provide a complete characterization of what the robot should look for in its configuration space to achieve globally convergent navigation. The approach thus provides a new framework, which will hopefully yield the first navigation algorithm that is both completely general and practical.     

Type-based initialization analysis of a synchronous dataflow language

One of the appreciated features of the synchronous dataflow approach is that a program defines a perfectly deterministic behavior. But the use of the delay primitive leads to undefined values at the first cycle; thus a dataflow program is really deterministic only if it can be shown that such undefined values do not affect the behavior of the system.This paper presents an initialization analysis that guarantees the deterministic behavior of programs. This property being undecidable in general, the paper proposes a safe approximation of the property, precise enough for most dataflow programs. This analysis is a one-bit analysis – expressions are either initialized or uninitialized – and is defined as an inference-type system with subtyping constraints. This analysis has been implemented in the Lucid Synchrone compiler and in a new Scade-Lustre prototype compiler at Esterel Technologies. The analysis gives very good results in practice.     

On the fuzzy difference equation xn+1 = A+B/xn

 In this paper we study the existence the oscillatory behavior the boundedness and the asymptotic behavior of the positive solutions of the fuzzy equation x _n+1 =A+B/x _n ,n=0,1,… where x _n is a sequence of fuzzy numbers, A, B are fuzzy numbers.     

A behavioral approach to the control of discrete linear repetitive processes

This paper formulates the theory of linear discrete time repetitive processes in the setting of behavioral systems theory. A behavioral, latent variable model for repetitive processes is developed and for the physically defined inputs and outputs as manifest variables, a kernel representation of their behavior is determined. Conditions for external stability and controllability of the behavior are then obtained. A sufficient condition for stabilizability is also developed for the behavior and it is shown under a mild restriction that, whenever the repetitive system is stabilizable, a regular constant output feedback stabilizing controller exists. Next, a notion of eigenvalues is defined for the repetitive process under an action of a closed-loop controller. It is then shown how under controllability of the original repetitive process, an arbitrary assignment of eigenvalues for the closed-loop response can be achieved by a constant gain output feedback controller under the above restriction. These results on the existence of constant gain output feedback controllers are among the most striking properties enjoyed by repetitive systems, discovered in this paper. Results of this paper utilize the behavioral model of the repetitive process which is an analogue of the 1D equivalent model of the dynamics studied in earlier work on these processes.