Abstract: Complexity associated with the design of experiments for simulation models can be reduced through visualization. DEVS-Suite, a new generation of the DEVS Tracking Environment which itself was extended from DEVSJAVA, supports visual design of experiments and introduces simulation data visualization. Data generated by the selected models can be collected dynamically and displayed as time-based trajectories. These capabilities complement animation of DEVS model components and their interactions. A service-oriented software system is modeled to illustrate the novel modeling features for DEVS simulations. Another example is developed in Ptolemy II and SimEvents to show the reduced visual complexity afforded by DEVS-Suite.

Abstract: Between discrete event simulation and evaluation within real networks, network emulation is a useful tool to study and evaluate the behaviour of applications. Using a real network as a basis to simulate another network's characteristics, it enables researchers to perform experiments in a wide range of conditions. After an overview of the various available network emulators, this paper focuses on three freely available and widely used network link emulators: Dummynet, NIST-Net, and the Linux Traffic Control subsystem. We start by comparing their features, then focus on the accuracy of their latency and bandwidth emulation, and discuss the way they are affected by the time source of the system. We expose several problems that cannot be ignored when using such tools. We also outline differences in their user interfaces, such as the interception point, and discuss possible solutions. This work aims at providing a complete overview of the different solutions for network emulation.

Abstract: Students studying topics in cyber security benefit from working with realistic training labs that test their knowledge of network security. Cost, space, time, and reproducibility are major factors that prevent instructors from building realistic networks for their students. This paper explores the ways that existing virtualization technologies could be packaged to provide a more accessible, comprehensive, and realistic training and education environment. The paper focuses on ways to leverage technologies such as operating system virtualization and other virtualization techniques to recreate an entire network environment consisting of dozens of nodes on moderately equipped hardware.

Abstract: Analysis of dependencies between technical systems and business processes is an important part of the discipline of Enterprise Architecture (EA). However, EA models typically provide only visual and qualitative decision support. This paper shows how EA frameworks for dependency analysis can be extended into the realm of quantitative methods by use of the Fault Tree Analysis (FTA) and Bayesian networks (BN) techniques. Using DoDAF -- the Department of Defense Architecture Framework -- as an example, we provide a method for how these EA models can be adapted for use of FTA and BN. Furthermore, we use this method to perform dependency analysis and scenario evaluation on a sample DoDAF model.

Abstract: A hybrid model is a combination of models developed in various simulation development environments. A war game model is a kind of hybrid model and consists of multiple level models. Engineering level models are interested in the change of values via time and process mathematical equations, and most of them are developed in MALTAB/Simulink. Engagement level models are concerned about state transitions by events and modeled using the Discrete Event Systems Specification (DEVS) formalism. This paper proposes a framework for interoperation of simulation tools for engineering and engagement level models simulation. The framework employs the High Level Architecture (HLA) to reuse existing models and suggests specific interfaces for MATLAB/Simulink. The proposed framework is demonstrated through simulation of a simple war game model including heterogenous models.

Abstract: As the fielding of enterprise systems of systems becomes common it becomes increasingly important to understand the interactions between the systems as well as the important role that human behavior plays. This paper suggests that Agent-Directed Simulation is a valuable and crucial analysis tool for the Systems Engineer. The paper examines the concept of Agent-Directed Simulation for Systems Engineering and then introduces the notion of Human Complex Systems. An analysis infrastructure is described and a case study is provided to illustrate the concepts.

Abstract: Crowd simulation has been becoming an efficient tool to study the crowd behavior and its movement. Macroscopic and microscopic approaches take a trade-off between efficiency and accuracy, but neither of them achieves the two goals at the same time. Aiming to achieve both efficiency and accuracy, a multi-resolution model is proposed in this paper for crowd simulation. The paper illustrates how macroscopic and microscopic models co-exist in a single simulator and the interactions between them. The simulation result of a case study shows that the proposed multi-resolution simulation model can obtain a more accurate result than that using a simple macroscopic model alone. The simulation performance is also improved in the meantime.

Abstract: As the Internet has become a more central aspect for information technology, so have concerns with supplying enough bandwidth and serving web requests to end-users in an appropriate time frame. Web caching help decrease bandwidth, lessen user perceived lag, and reduce loads on origin servers by storing copies of web objects on servers closer to end users as opposed to forwarding all requests to the origin servers. Since web caches have limited space, web caches must effectively decide which objects are worth caching or replacing for other objects. This problem is known as cache replacement. We used neural networks to solve this problem and proposed the Neural Network Proxy Cache Replacement (NNPCR) method. In this paper we propose an improved strategy of NNPCR referred to as NNPCR-2. We implemented NNPCR-2 in Squid proxy server and compared it with four other cache replacement strategies. In this paper we use 84 times more data than NNPCR was tested against and present exhaustive test results for NNPCR-2 with different trace files and neural network structures. Our results demonstrate that NNPCR-2 made important, balanced decisions in relation to the hit rate and byte hit rate; the two performance metrics most commonly used to measure the performance of web proxy caches.

Abstract: DEVS Modeling and Simulation (M&S) has various implementations with various computer languages such as JAVA, C++, and C#. To enhance model reusability with different implementation, we need interoperable systems such as CORBA, HLA, and SOA, and an interoperable mechanism for simulation of heterogeneous DEVS models. As an infrastructure of an interoperable system, SOA is applicable because it provides platform and language independence. In this paper, we apply DEVS/SOA system to embody interoperability between heterogeneous DEVS models. Also, we define common DEVS simulator interface required to simulate DEVS models. To expose simulators' ports information described in XML schema type, the interface has additional description operations. The XML schema type is registered into DEVS namespace which is common place to look up the schema type for ports when heterogeneous DEVS models are integrated through DEVS simulation service integration/execution which we propose. We will illustrate the example of DEVS simulator interoperability with DEVSJAVA and ADEVS models which is implemented with JAVA and C++, respectively

Abstract: We present DFTSim, a simulation tool for dynamic fault trees (DFT). The simulation is carried out by directly sampling the failure distributions attached to the leaves (called basic events) of the tree and propagating the failure times upwards in the tree.Sampling the distributions of the DFT leaves is however not obvious. To sample from the correct distributions, the analytical expression of the failure distributions of all basic events (BE) must be known. These are indeed known for non-spare BEs; but for spare BEs, they become conditional on the failure of other BEs. Hence, the derivation of the analytical expression of the spares' failure distributions and their sampling is not a trivial task.We evaluate DFTSim by applying it on an extensive benchmark comprised of seven case studies. We compare its results to two other DFT-based reliability tools (namely Galileo and Coral) that, rather than giving simulation-based estimates, compute exact measures.Our simulation-based approach is, in particular for large DFTs, much faster than the existing approaches. In fact, the computation time of the exact solution methods is exponential in the number of DFT leaves, whereas simulation time is linear in the number of leaves. Moreover, DFTSim (and simulation in general) allows to simulate a wide range of distributions and evaluate Markovian as well as non-Markovian models.

Abstract: One approach to support the creation of executable UML models is to utilize an existing DEVS simulation environment. The Discrete Event System Specification (DEVS) formalism excels at modeling complex discrete event systems. An approach to specifying DEVS-compliant models is presented via Unified Modeling Language (UML) state machines. Resultant UML models are executable within DEVS simulation frameworks such as DEVSJAVA. Constructing DEVS-compliant UML models enables early simulation and verification of a design. This paper outlines how the specifics of simulation can be naturally expressed in UML models without significant burden to the UML practitioner. Simulatable models are an excellent precursor and companion to the current models normally developed during design and implementation and may result in significant cost and time savings.

Abstract: This paper specifies a systems engineering process for the development of federated simulation models in order to support systems-of-systems analysis. The specification borrows ideas from the systems engineering domain, the simulation interoperability domain, and the software engineering domain. It has activities on the operational level to define how the real system operates, the system level to define the overall architecture of the federation, and the technical level to fully specify requirement to model developers. Use of this process allow the developers of federated simulations to separate these concerns and dialog more effectively with all of these groups.

Abstract: In this paper, we introduce a new approach for wireless sensor networks management which is an improved version of previously proposed methods, using the concept of Multi-Agent Systems. From a software point of view, wireless sensor networks need to be managed in many different ways; e.g. power consumption in each sensor, efficient data routing, sensing and data sending interval, etc. Our approach gives the network a more structured model, and manages the former issues using multi-agent system concepts. In our model, we propose a new method for sensor power management which we call Neighbors Power Comparison (NPC). We defined 4 different power thresholds, and when the sensor's power meets each one of these thresholds a power reduction algorithm will try to reduce the amount of energy used by sensor. We also cover the whole life-time process of a sensor network using our model.

Abstract: A current notable effort in the DEVS community is to provide a worldwide platform for distributed modeling and simulation based on Web Services and related technologies. Such an infrastructure will allow the sharing and reuse of simulation models and experiments. This will permit attacking different aspects of interoperability at the right level of abstraction: the simulation-based interoperability at the level of the data transfer between components in a distributed simulation, the model-based interoperability to share models and experiments, and other dimensions, including syntactic, semantic, and pragmatic interoperability. An essential requirement is that a common, unique and complete representation must be adopted to store, retrieve, share and make interoperable simulation models. Such a representation must take into account all the aspects included in all possible use cases. This work deals with this issue and proposes an XML-based language that can serve as a basis for defining a standard for distributed simulation linking DEVS and non-DEVS simulations.

Abstract: The development of simulation models for complex systems can be difficult and time consuming. This makes the ability to re-use modelling components of high value. To be able to re-use modeling components it is important to know the context within which a given component was developed. Experimental Frames are useful for capturing this context. We present the CD++ Repository -- an internet based searchable database of re-usable CD++ DEVS models and their Experimental Frames. CD++ Repository facilitates the re-use of models and allows users in different geographical locations to collaborate in building complex models. The database is built as a hierarchy of the stored atomic and coupled models, thus eliminating repetition. One of the key features is that along with the storage of the atomic and coupled models, it stores Experimental Frames for each model, which allows users to easily determine the context for which a given model applies.

Abstract: A fundamental issue in data assimilation of wildfire simulation is to estimate the dynamically changing states, e.g., the fire front position of wildfire, based on observation data of fire sensors. This is a challenging task because of the dynamic and non-linear behavior of fire spread. In this paper, we apply particles filters, also called sequential Monte Carlo methods, to data assimilation in wildfire simulation for estimating the dynamically evolving fire front of a spreading fire. The framework of applying particle filters to the DEVS-FIRE simulation model is presented. Preliminary experiment results show that the particle filtering algorithm was able to track the dynamically changing fire front based on fire sensor data, and thus to provide more accurate predictions of wildfire spread.

Abstract: Web service technology is used to augment software reusability and composability providing XML-based message passing and operating system platform neutralization. Business Process Execution Language (BPEL) is commonly used to integrate web services called business processes, and implementations of BPEL vary according to venders. BPEL components have simple behavior. In this paper, we propose automatic generated DEVS interface to web services to apply a formal method to orchestrating web services to provide dynamic testing environment of business processes with DEVS modeling and simulation and to enhance the reusability of business processes and interoperability of instances of BPEL. We will show an environment of DEVS interface for Web Services to integrate and execute web services, and describe its components such as integration of web services, a XML document describing the integration, and creation and execution of DEVS models with a mechanism of dynamic invocation of web services.

Abstract: A variety of ad hoc routing protocols based on a simple flooding routing method have been developed under the constraints of the limited transmission range of wireless network interfaces and other limited mobility resources in MANETs. In this paper we discuss the performance of a gossip-based routing and flooding protocol based on ad hoc on-demand routing protocols in order to identify the strengths and weaknesses of each protocol and suggest appropriate MANET environments for each routing protocol. To accomplish our goals, we selected six performance metrics: packet delivery fraction, average end-to-end delay of data packets, routing overhead, normalized routing load, throughput, and average node energy used. We performed simulations of three ad hoc routing protocols: AODV+G, AODV, and DSR, using the ns-2 network simulation tool.

Abstract: Ensuring cyber related personnel are properly trained is vital to maintaining and defending our country's network and computer infrastructure. The Air Force provides formal technical training schools, on-line computer based training, and training exercises to achieve this goal. However, local on-the-job training conducted by field supervisors needs to be focused towards hands-on system training to keep the trainee's skills current. Unfortunately, continual training can be difficult to accomplish since system down-time is not an option to provide training, due to high demand supporting real-world missions. This paper looks at the software training tools available in the realm of virtual machines, their strengths and weaknesses, and demonstrates application in training the next generation of cyber warriors.

Abstract: In this paper we present the construction of a standardized adjoint of the global GEOS-Chem model. Adjoint models are powerful tools for estimating the sensitivity of (a function of) the model output with respect to a large number of inputs. The construction of adjoint models is a difficult, labor intensive, and error prone task. The adjoint of gas phase chemistry is generated using the Kinetic PreProcessor (KPP) and parsers to automatically interface KPP with GEOS-Chem are constructed. The adjoints of other individual science processes are generated manually and using automatic differentiation tools, and are validated extensively against finite-differences. The standardized adjoint framework discussed here will allow the world-wide community of GEOS-Chem users to perform sensitivity analyses and 4-D variational data assimilation for initial tracer concentrations, boundary conditions, and emission sources.

Abstract: In this paper we describe a new simulation platform for complex wireless sensor networks that operate a collection of distributed algorithms and network protocols. Simulating such systems is complicated because of the need to coordinate different network layers and debug protocol stacks, often with very different interfaces, options, and fidelities. Our platform (which we call WSNGE) is a flexible and extensible environment that provides a highly scalable simulator with unique characteristics. It focuses on user friendliness, providing every function in both scriptable and visual way, allowing the researcher to define simulations and view results in an easy to use graphical environment. Unlike other solutions, WSNGE does not distinguish between different scenario types, allowing multiple different protocols to run at the same time. It enables rich online interaction with running simulations, allowing parameters, topologies or the whole scenario to be altered at any point in time.

Abstract: We propose DDML (DEVS-Driven Modeling Language), a graphical notation for DEVS modeling and simulation. This notation aims at providing a way to drive easily the modeling activity (by drawing and linking graphical symbols and augmenting them with text), and to catch at the same time the results of the simulation activity. This means that both structure and behavior are concerned by this notation and that static, dynamical and functional aspects are all shown. DDML integrates strong modeling concepts from powerful formalisms and glue them in one unique consistent framework.

Abstract: As we know Internet have grown rapidly in the past few years, and one of the prevalent problems of World Wide Web is increasing network traffic. It has been shown that caching is valuable technique that reduces network traffic. However, still it has some problems such as performance problem. This paper proposes a novel way to solve those problems efficiently by introducing the evolutionary computing technique for cache replacement policy.

Abstract: Traditionally, defense uses human-based warfare simulation to assess risks, optimize missions, and make operational, tactical and strategic decisions. However, this approach is extremely expensive and does not enable analysts to explore all aspects of the problem or emergent behavior. The major goal of this paper is first to propose an AEEE principle (Abstraction, Endomorphism, Encapsulation, and Evolution) for designing an evolutionary intelligent agent system and then to introduce a FAMES (Fully Agent-based Modeling & Emergent Simulation) framework as a realization of AEEE principle that can extract the suitable tactics/strategies in the warfare environment. By combining the top-down paradigm for the constructive simulation with the bottom-up paradigm for the emergent simulation to model the agent-based warfare environment, FAMES is able to generate lots of possible simulation trajectories according to the evolution process for finding suitable tactical/strategic solution. To do this, we have employed the advanced modeling and simulation environment, SES/MB (System Entity Structure / Model Base) environment that can support suitable basis to model the event-based nature of the warfare behavior with evolutionary intelligent agent system. The intelligent battleship agent system has been successfully implemented and tested to demonstrate the emergent behavior of proposed framework.

Abstract: The absence of standarization could delay the progress of novel technological advances. Whereas, the guidance of uniform engineering specifications aims to amplify interoperability uppon systems. Extending functionality among different modeling and simulation frameworks opens a broad outreach to researchers. In this paper, we propose an approach supporting interoperability among DEVS compilant models and Matlab functionality in consort with a multi-platform web-based distributed simulation framework handling The Service oriented Architecture (SOA). To prevent the lack of homogeneous criteria, we employ recently developed interoperability concepts accompanied by Discrete EVent System (DEVS) Specification formalism to implement a standard for interoperability: a distributed simulation environment involving the DEVS/SOA JAVA and .NET simulation engines to simulate DEVS and non-DEVS models. Furthermore, we present a distributed sample model following the DEVS models specification interface while integrating Matlab utilities.

Abstract: All of the military services are actively seeking improved tools and methods for providing warfighters with improved situation awareness of battlefield conditions. RAM Laboratories is working to emphasize the advantages of moving simulation activities away from big, complex, vertically integrated simulation systems running on dedicated high-powered platforms. We are moving instead towards a new model of service-oriented simulation providing access to modular domain-specific simulation models that fully support dynamic composition and varying patterns of connectivity between multiple light-weight nodes. These distributed simulation capabilities can be readily combined with advanced analysis techniques, including knowledge inferencing and hypothesis testing, within a service-oriented architecture (SOA) framework to provide situation awareness solutions that are robust and resilient to the effects of incomplete and unreliable data sources.The paper discusses the design of a service-oriented simulation software framework as part of a broader approach towards generating improved levels of actionable views of situation awareness; an approach that aligns and scales with current trends towards the increased use of SOA and cloud computing technologies. The paper describes design features that enable powerful and flexible access to distributed simulation capabilities, increased opportunities for software component reuse, and rapid development and deployment of new applications utilizing multiple levels of simulation capabilities.

Abstract: Diffusion is the process in which the successful introduction of new products and practices into society along with invention Many studies of the diffusion of individual innovations exist, and exhibit some commonalities such as the famous S-shaped diffusion curve New ideas, products, and innovation often take time to diffuse, a fact that is often attributed to some form of heterogeneity among people Then a basic puzzle posed by innovation diffusion is why there is often a long lag between an innovation's first appearance and the time when a substantial number of people have adopted it There is an extensive theoretical and empirical literature on this phenomenon and the mechanisms that might give rise to it The diffusion process enhances an innovation via the feedback of information about its utility across different users that can be used to improve it This aspect is similar to the micro-macro loop which is essential part of emergent dynamics

Abstract: Discrete event simulators are getting more complex due to a variety of requirements that include desired functions and properties. Therefore, verifying and testing the discrete event simulator is a complicated problem. Moreover, if the simulator is already implemented, inserting and deleting tracing/logging code into the source code of a simulator may cause the code tangling and the code scattering problems. This paper proposes the Aspect embedded DEVS Verification Framework. The Aspect embedded DEVS Verification Framework utilize Aspect Oriented Programming features to handle the code tangling and the code scattering problems. By applying aspect oriented feature, user can find and fix the inconsistency between requirement and implementation of simulator without suffering the code tangling and the code scattering problems. The first step of the verification process is verifying DEVS diagrams to show that the DEVS diagrams are satisfied with the requirement specifications. The second step is checking the event traces from the simulator compared with the possible execution sequences from DEVS diagrams.

Abstract: We are witnessing these days a rapid growth of mobile users. Therefore, frequency spectrum must be efficiently utilized, as available frequency spectrum is limited. This paper proposes a channel allocation scheme with efficient bandwidth reservation which initially reserves some channels for handoff calls, and later reserves the channels dynamically, based on the user mobility. QoS can be improved further if the channel reservation is made based on the location of the user. We devise here a new algorithm that deals with multiple traffic systems by modifying existing DDCA algorithm [1]. This algorithm reserves more channels for hot cells, few channels for cold cells and reserves channels on an average for the medium cells. Furthermore, we maintain queues for all types of calls. We compute the QoS parameters in terms of the blocking probability of originating calls and the dropping probability of handoff calls. The results indicate that the proposed channel allocation scheme exhibits better performance by considering the above mentioned user mobility, type of cells, and maintaining of the queues for various traffic sources. In addition, it can be observed that the dropping probability can be reduced by using reservation factor dynamically using our approach.