Computing by observing: Simple systems and simple observers

We survey and extend the work on the paradigm called “computing by observing”. Its central feature is that one considers the behavior of an evolving system as the result of a computation. To this purpose an external observer records this behavior. In this way, several computational trade-offs between the observer and the observed system can be determined. It has turned out that the observed behavior of computationally simple systems can be very complex, when an appropriate observer is used. For example, a restricted version of context-free grammars with regular observers suffices to obtain computational completeness. As a second instantiation presented here, we apply an observer to sticker systems, an abstract model of DNA computing. Finally, we introduce and investigate the case where the observers can read only one measure of the observed system (e.g., mass or temperature), modeling in this way the limitations in the observation of real physical systems. Finally, a research perspective on the topic is presented.     

Construction method of shop-floor digital twin based on MBSE

Digital twin (DT) technology is essential for achieving the fusion of virtual-real cyber-physical systems. Academics and companies have made great strides in the theoretical research and case studies of constructing the shop-floor digital twin (SDT), which is the premise of applying DT technology on the shop floor. A shop floor is a large complex system that involves many elements including people, machines, materials, methods, and the environment and processes, such as the technical flow, business process, logistics, and control flow. However, most of the developed cases lack a hierarchical, structured and modularized implementation framework for the development of an SDT system, which leads to problems such as a low reuse rate of the system blocks, lack of scalability, and high upgrade and maintenance costs. In response to these issues, we propose a construction method of the DT for the shop floor based on model-based systems engineering from the perspective of the system. In this method, a comprehensive DT model for the shop floor is gradually constructed by using system modeling language, the modeling method “MagicGrid,” and the “V model” of systems engineering. The model includes four dimensions of the shop-floor requirements, structure, behavior, and parameters, as well as three stages (the problem domain, solution domain, and implementation domain), and connects nine steps of the “V model,” including the system requirements, system architecture, subsystem implementation, subsystem integration, and system verification. Then, based on an example of a real NC machining shop floor, subsystems including a visualization system, synchronization system, and simulation system, are discussed. Finally, the functions of the integrated systems are verified based on the requirements, including the real-time synchronization of “man, machine, material, and method” and the transient simulation in real time. The numerical indicators of the integrated system are verified, including the model completeness and synchronization timeliness.     

Holdings about holdings: modeling contradictions in judicial precedent

This paper attempts to formalize the differences between two methods of analysis used by judicial opinions in common law jurisdictions to contradict holdings posited by earlier opinions: “disagreeing” with the holdings of the earlier opinions and “attributing” holdings to the prior opinions. The paper will demonstrate that it is necessary to model both methods of analysis differently to generate an accurate picture of the state of legal authority in hypothetical examples, as well as in an example based on Barry Friedman’s analysis of the “stealth overruling” of Miranda v. Arizona through subsequent judicial interpretations. Because the question of whether “disagreement” and “attribution” need to be modeled separately relates to contradictions rather than to subtler interactions between holdings such as “distinguishing,” it can be answered using the simple technique of modeling holdings as propositional variables and evaluating the holdings using truth tables.     

WHOLENESS,GESTALT, SYSTEM: ON THE MEANING OF THESE CONCEPTS EN GERMAN LANGUAGE

Trying to compare the concepts of wholeness and system as they have been used and interpreted by theorists, we will find that the majority of them are inclined to consider a system as a kind of wholeness, but not in its traditional meaning: not in the sense of a substantial wholeness with a loss of the element's individual being or with assuming an entelechial “wholemaking” factor; however, they think of a wholeness is “more than the sum of its parts”, with an order, an organization, or a structure, and in which we can find characteristic laws, as for example in atoms and molecules, in cells and human societies. And this, at bottom, is also the position of gestall-psychologisls with respect to their concept or gestalt.

Thus, it seems that modem interpretations of wholeness, gestalt, and system do not diverge too Tar, But, nevertheless. I find that there exists a profound difference: system-concepts are largely based on a mechanistic-organicistic view, where no coherences exist “behind the scientific world”, no objective spirit, at most an objectivated or a “third world” (Popper), and for which all evolved is pure epiphenomenon resulting from the etemeats immanent forces. On the other hand the concept of wholeness can never be comprehended without a metaphysical anchorage of the phenomenon of wholeness in the order of being, and it is emphasized that reality is more complex than what we can rationalize and measure of it.     

ON A LOGISTIC-HIDDEN MARKOV MODEL FOR COMMUNICATION SYSTEMS

This article proposes an extension of hidden Markov models for communication systems by allowing the Markovian transitions between the channel's states to be influenced by an external “catalyzer” (i.e., environmental or experimental conditions). The stochastic influence of the catalyzer is expressed by logistic link functions. The model can be useful for modeling communication channels, for example, in predicting single-ion channel behavior for cell signaling. A simulation study is provided in order to explore how trainable the model is. We prove that the Logistic-Hidden Markov model can be very well trained by means of the maximum likelihood method, assisted by a modified Baum–Welch algorithm.     

Cellular Homeostasis,Epigenesis and Replication in Randomly Aggregated Macromolecular Systems

Abstract

Proto-organisms probably were randomly aggregated nets of chemical reactions. The hypothesis that contemporary organisms are also randomly constructed molecular automata is examined by modeling the gene as a binary (on-off) device and studying the behavior of large, randomly constructed nets of these binary “genes.” The results suggest that, if each “gene” is directly affected by two or three other “genes,” then such random nets: behave with great order and stability; undergo behavior cycles whose length predicts cell replication time as a function of the number of genes per cell; possess different modes of behavior whose number per net predicts roughly the number of cell types in an organism as a function of its number of genes; and under the stimulus of noise are capable of differentiating directly from any mode of behavior to at most a few other modes of behavior. Cellular differentiation is modeled as a Markov chain among the modes of behavior of a genetic net. The possibility of a general theory of metabolic behavior is suggested. Analytic approaches to the behavior of switching nets are discussed in Appendix 1, and some implications of the results for the origin of self replicating macromolecular systems is discussed in Appendix 6.     

Prediction of traveling front behavior in a lattice-gas cellular automaton model for tumor invasion

Cancer invasion is the process of cells detaching from a primary tumor and infiltrating the healthy tissue. Cancer invasion has been recognized as a complex system, since a tumor’s invasive behavior emerges from the combined effect of tumor cell proliferation, tumor cell migration and cell–microenvironment interactions. Cellular automata (CA) provide simple models of self-organizing complex systems in which collective behavior can emerge out of an ensemble of many interacting “simple” components. Here, we introduce a lattice-gas cellular automaton (LGCA) model of tumor cell proliferation, necrosis and tumor cell migration. The impact of the tumor environment on tumor cells has been investigated in a previous study. Our analysis aims at predicting the velocity of the traveling invasion front, which depends upon fluctuations that arise from the motion of the discrete cells at the front. We find an excellent agreement between the velocities measured in simulations of the LGCA and an analytical estimate derived in the cut-off mean-field approximation via the discrete Lattice Boltzmann equation and its linearization. In particular, we predict the front velocity to scale with the square root of the product of probabilities for mitosis and the migration coefficient. Finally, we calculate the width of the traveling front which is found to be proportional to the front velocity.     

“Virtual laboratory environment” (VLE): a software environment oriented agent and object for modeling and simulation of complex systems

Our research relates to multi-agent and oriented object modeling and simulation of the complex systems. Our research interest itself more particularly with system where the spatial and temporal component make a great part of system to model (for example, ecosystems or systems of production). Within the framework of this article, we will be interested in the flexible production systems.The simulation of complex systems requires generally the integration and the coupling of heterogeneous models (multi-agent, mathematical, and so on). This heterogeneity is a consequence of the diversity of the disciplines and abilities of designers. The approach that we develop consists in the development of “virtual laboratories ”. Our platform “virtual laboratory environment” (VLE) enables us to specify, simulate and analyze spatial complex systems. VLE is based on the concepts of reactive agents, objects and spatial and temporal multi-scale systems.     

Fuzzy system based human behavior recognition by combining behavior prediction and recognition

With the development of intelligent surveillance systems, human behavior recognition has been extensively researched. Most of the previous methods recognized human behavior based on spatial and temporal features from (current) input image sequences, without the behavior prediction from previously recognized behaviors. Considering an example of behavior prediction, “punching” is more probable in the current frame when the previous behavior is “standing” as compared to the previous behavior being “lying down.” Nevertheless, there has been little study regarding the combination of currently recognized behavior information with behavior prediction. Therefore, we propose a fuzzy system based behavior recognition technique by combining both behavior prediction and recognition. To perform behavior recognition during daytime and nighttime, a dual camera system of visible light and thermal (far infrared light) cameras is used to capture 12 datasets including 11 different human behaviors in various surveillance environments. Experimental results along with the collected datasets and open database showed that the proposed method achieved higher accuracy of behavior recognition when compared to conventional methods.     

Does aspect-oriented modeling help improve the readability of UML state machines?

Aspect-oriented modeling (AOM) is a relatively recent and very active field of research, whose application has, however, been limited in practice. AOM is assumed to yield several potential benefits such as enhanced modularization, easier evolution, increased reusability, and improved readability of models, as well as reduced modeling effort. However, credible, solid empirical evidence of such benefits is lacking. We evaluate the “readability” of state machines when modeling crosscutting behavior using AOM and more specifically AspectSM, a recently published UML profile. This profile extends the UML state machine notation with mechanisms to define aspects using state machines. Readability is indirectly measured through defect identification and fixing rates in state machines, and the scores obtained when answering a comprehension questionnaire about the system behavior. With AspectSM, crosscutting behavior is modeled using so-called “aspect state machines”. Their readability is compared with that of system state machines directly modeling crosscutting and standard behavior together. An initial controlled experiment and a much larger replication were conducted with trained graduate students, in two different institutions and countries, to achieve the above objective. We use two baselines of comparisons—standard UML state machines without hierarchical features (flat state machines) and standard state machines with hierarchical/concurrent features (hierarchical state machines). The results showed that defect identification and fixing rates are significantly better with AspectSM than with both flat and hierarchical state machines. However, in terms of comprehension scores and inspection effort, no significant difference was observed between any of the approaches. Results of the experiments suggest that one should use, when possible, aspect state machines along with hierarchical and/or concurrent features of UML state machines to model crosscutting behaviors.     

Formal verification of SysML diagram using case studies of real-time system

System and software engineers use SysML models for the graphical modeling of the embedded systems. The SysML models are inadequate to express the discrete controllers with continuously evolving variables. The real-time constraints such as discrete and continuous dynamics are considered to be an important aspect in embedded systems. The lack of support of real-time aspect in SysML model can lead to inexplicit modeling of the embedded systems. The imprecise modeling could cause catastrophic results when an embedded system gets operational. In this paper, we propose hybrid automata-based semantics that supports the discrete and continuous behavior in upgraded SysML block diagram. The upgraded SysML block diagram is used for the modeling of the embedded system. Furthermore, we use model checker PRISM for the early design verification of upgraded SysML block diagram. Finally, we demonstrate the effectiveness of our proposed approach with the help of two case studies “temperature control system” and “water level control system”.

     

The idealized structural unit method and its application to deep girder structures

An efficient method of analysis of non-linear behavior until collapse of large size redundant structures is presented. The method is named as The “Idealized Structural Unit Method”. In this method the structure is divided into the biggest possible “Structural Units” whose geometric and material nonlinear behavior can be idealized and described in a concise analytical-numerical form. The structure is reassembled and load is applied incrementally until ultimate strength is attained.In this method, modeling is an obvious operation of dividing the structure into its actual structural units. This eliminates the effort required for the choice of type of element or size of mesh as in the finite element method. The number of structural units and overall degrees of freedom required for the analysis of a structure by this method are less in order than the number of elements and overall degrees of freedom required to analyze the same structure by the FEM. Costs of computer and data preparation may be drastically reduced.Application of the method to metal structures built up of deep I girders, such as bridge girders, ships deep girders and grillage structures is considered. The “Girder Structural Unit” is defined and its behavior under increasing loads is idealized based on existing as well as newly developed theoretical and experimental studies. Conditions for web bucking, ultimate strength and full plastic strength are established and expressions for stiffness during various stages are derived. A deep girder structure may then be treated as an assembly of such “Girder Structural Units”. Results of analysis of example structures are presented. The consumed computer time is found to be very short, as expected. Comparisons with results of experimental studies show good agreement.     

Usage of SoS methodologies in production system design

Production systems design is a multifaceted task, due to a variety of aspects such as the mutual interdependency between the sub-systems, the variety of configurations and alternative system control strategies, the multiple managerial and “soft” aspects that cast an influence on the behavior of the system. A reasonable number of modeling tools can be applied to production system design, but they tend to divide the problem into unconnected sub-problems whose individual solutions may result in a poor global one. This is despite the fact that production design encompasses all aspects of manufacturing operations, and needs a systemic approach, as clearly shown in practitioner-oriented literature. This paper proposes to apply the “System of Systems” approach to production system design in order to represent their main aspects and support the rational definition of the path leading from corporate strategy to system (re)design.     

Structural simplification of modular bond-graph models based on junction inactivity

The modular modeling paradigm facilitates the efficient building, verification and handling of complex system models by assembling them from general-purpose component models. A drawback of this paradigm, however, is that the assembled system models may have excessively complex structures for certain purposes due to the amount of detail in the component models that has been introduced to promote modularity. For example, a multibody system can be modeled using generic rigid-body models with 6 degrees-of-freedom (DoF) to represent the components of the system, but then constraints have to be added to the model to match the DoF of the system. This work presents a structural simplification technique that can detect such unnecessary complexities in a modular bond-graph system model and eliminate them without compromising accuracy. To this end, the activity concept in the literature is extended to define “inactivity” for junction elements, and simplification is obtained by detecting and eliminating inactive junction elements and by propagating the implications. It is shown by example that this simple idea can result in models that are conceptually and computationally more efficient than the original modular models. The realization-preserving and input-dependent characteristics of this approach are highlighted.     

Microbial ecology and bioprocess control: Opportunities and challenges

This paper aims at emphasizing the importance of a systemic approach together with new investigation tools provided by molecular biology to give new insights into microbial ecology. Through the presentation of four recently obtained results about the coexistence of species in competition on a single resource, it is argued that such an approach can have major impact on ecological problems. In the first example, we revisit the existing models of biotechnology and show how they can be updated in some sense to better describe the real world by taking into account the spatial heterogeneity in a very simple but effective way (in the sense that their qualitative predictions are in accordance with the observed data). In the second example, we show how an optimally designed biosystem may give insights to the understanding of the so-called barrier effect. The third example proposes a new explanation for coexistence, that we called “long run coexistence”, in studying the transient behavior of a high dimensional system describing N species in competition on a single substrate. Finally, a last example presents the original concept of “biological control” which refers to the use of a particular species to globally stabilize an unstable biological process.     

Complex agent networks: An emerging approach for modeling complex systems

Complexity and complex systems are all around us: from molecular and cellular systems in biology up to economics and human societies. There is an urgent need for methods that can capture the multi-scale spatio-temporal characteristics of complex systems. Recent emphasis has centered on two methods in particular, those being complex networks and agent-based models. In this paper we look at the combination of these two methods and identify “Complex Agent Networks”, as a new emerging computational paradigm for complex system modeling. We argue that complex agent networks are able to capture both individual-level dynamics as well as global-level properties of a complex system, and as such may help to obtain a better understanding of the fundamentals of such systems.     

QoS Assessment of Mobile Crowdsensing Services

The wide spreading of smart devices drives to develop distributed applications of increasing complexity, attracting efforts from both research and business communities. Recently, a new volunteer contribution paradigm based on participatory and opportunistic sensing is affirming in the Internet of Things scenario: Mobile Crowdsensing (MCS). A typical MCS application considers smart devices as contributing sensors able to produce geolocalized data about the physical environment, then collected by a remote application server for processing. The growing interest on MCS allows to think about its possible exploitation in commercial context. This calls for adequate methods able to support MCS service providers in design choices, implementing mechanisms for the quality of service (QoS) assessment while dealing with complex time-dependent phenomena and churning issues due to contributors that unpredictably join and leave the MCS system. In this paper, we propose an analytical modeling framework based on stochastic Petri nets to evaluate QoS metrics of a class of MCS services. This method requires to extend the Petri net formalism by specifying a marking dependency semantics for non-exponentially distributed transitions. The approach is then applied to an MCS application example deriving some QoS measures that can drive quantitative evaluation and characterization of the “crowd” behavior.     

Modeling robustness behavior using aspect-oriented modeling to support robustness testing of industrial systems

Model-based robustness testing requires precise and complete behavioral, robustness modeling. For example, state machines can be used to model software behavior when hardware (e.g., sensors) breaks down and be fed to a tool to automate test case generation. But robustness behavior is a crosscutting behavior and, if modeled directly, often results in large, complex state machines. These in practice tend to be error prone and difficult to read and understand. As a result, modeling robustness behavior in this way is not scalable for complex industrial systems. To overcome these problems, aspect-oriented modeling (AOM) can be employed to model robustness behavior as aspects in the form of state machines specifically designed to model robustness behavior. In this paper, we present a RobUstness Modeling Methodology (RUMM) that allows modeling robustness behavior as aspects. Our goal is to have a complete and practical methodology that covers all features of state machines and aspect concepts necessary for model-based robustness testing. At the core of RUMM is a UML profile (AspectSM) that allows modeling UML state machine aspects as UML state machines (aspect state machines). Such an approach, relying on a standard and using the target notation as the basis to model the aspects themselves, is expected to make the practical adoption of aspect modeling easier in industrial contexts. We have used AspectSM to model the crosscutting robustness behavior of a videoconferencing system and discuss the benefits of doing so in terms of reduced modeling effort and improved readability.