101 research outputs found
An Agent Based Model to Assess Crew Temporal Variability During U.S. Navy Shipboard Operations
Understanding the factors that affect human performance variability as well as their temporal impacts is an essential element in fully integrating and designing complex, adaptive environments. This understanding is particularly necessary for high stakes, time-critical routines such as those performed during nuclear reactor, air traffic control, and military operations. Over the last three decades significant efforts have emerged to demonstrate and apply a host of techniques to include Discrete Event Simulation, Bayesian Belief Networks, Neural Networks, and a multitude of existing software applications to provide relevant assessments of human task performance and temporal variability. The objective of this research was to design and develop a novel Agent Based Modeling and Simulation (ABMS) methodology to generate a timeline of work and assess impacts of crew temporal variability during U.S. Navy Small Boat Defense operations in littoral waters. The developed ABMS methodology included human performance models for six crew members (agents) as well as a threat craft, and incorporated varying levels of crew capability and task support. AnyLogic ABMS software was used to simultaneously provide detailed measures of individual sailor performance and of system-level emergent behavior. This methodology and these models were adapted and built to assure extensibility across a broad range of U.S. Navy shipboard operations. Application of the developed ABMS methodology effectively demonstrated a way to visualize and quantify impacts/uncertainties of human temporal variability on both workload and crew effectiveness during U.S. Navy shipboard operations
Surveying navigation modelling approaches
Recently, a number of authors who work on web application modelling have paid attention to the ideas regarding
separation of concerns that underlie aspect-orientation, as well as some ideas that come from the model-driven development
community. They attempt to improve the representation and separation of some concerns such as customisation or navigational
concerns that are scattered throughout different software artifacts and tangled with other concerns in order to give a best support to
the evolution of web applications. This paper surveys recent proposals in this field and compares them within a homogeneous
framework that bridges the gap between the many different terminologies used, and highlights open problems that need further
research.Ministerio de Ciencia y TecnologĂa TIN2007-64119Ministerio de Ciencia y TecnologĂa TIN-2007-67843-C06-0
Extending Business Process Models with Appreciation
We use homeostasis, the maintenance of steady states in an organism, to explain some of the decisions made by participants in a business process. We use Vickers’ Appreciative System to model the homeostatic states with Harel’s statecharts. We take the example of a doctoral student recruitment process formally defined between a faculty member, a graduate student candidate and a doctoral school. We analyze some gaps in the process caused by a misfit between norms of the process participants. We present a rationale for the anticipation and resolution of these misfits. We extend the traditional operational model with an appreciative model. This model represents the appreciative systems of process participants. Understanding these appreciative systems is necessary to make explicit the misfit between the model and the observed reality. The operational model represents the “technical” perspective on the business process, the one that can be automated. The appreciative model represents the “social” perspective, the one that explains the participants’ behavior as a result of their individual and collective norms. By combining these two perspectives, we can appreciate the richness of the development of socio-technical systems
WS-Pro: a Petri net based performance-driven service composition framework
As an emerging area gaining prevalence in the industry, Web Services was established to satisfy the needs for better flexibility and higher reliability in web applications. However, due to the lack of reliable frameworks and difficulties in constructing versatile service composition platform, web developers encountered major obstacles in large-scale deployment of web services. Meanwhile, performance has been one of the major concerns and a largely unexplored area in Web Services research. There is high demand for researchers to conceive and develop feasible solutions to design, monitor, and deploy web service systems that can adapt to failures, especially performance failures. Though many techniques have been proposed to solve this problem, none of them offers a comprehensive solution to overcome the difficulties that challenge practitioners.
Central to the performance-engineering studies, performance analysis and performance adaptation are of paramount importance to the success of a software project. The industry learned through many hard lessons the significance of well-founded and well-executed performance engineering plans. An important fact is that it is too expensive to tackle performance evaluation, mostly through performance testing, after the software is developed. This is especially true in recent decades when software complexity has risen sharply. After the system is deployed, performance adaptation is essential to maintaining and improving software system reliability. Performance adaptation provides techniques to mitigate the consequence of performance failures and therefore is an important research issue. Performance adaptation is particularly meaningful for mission-critical software systems and software systems with inevitable frequent performance failures, such as Web Services.
This dissertation focuses on Web Services framework and proposes a performance-driven service composition scheme, called WS-Pro, to support both performance analysis and performance adaptation. A formalism of transformation from WS-BPEL to Petri net is first defined to enable the analysis of system properties and facilitate quality prediction. A state-transition based proof is presented to show that the transformed Petri net model correctly simulates the behavior of the WS-BPEL process. The generated Petri net model was augmented using performance data supplied by both historical data and runtime data. Results of executing the Petri nets suggest that optimal composition plans can be achieved based on the proposed method.
The performance of service composition procedure is an important research issue which has not been sufficiently treated by researchers. However, such an issue is critical for dynamic service composition, where re-planning must be done in a timely manner. In order to improve the performance of service composition procedure and enhance performance adaptation, this dissertation presents an algorithm to remove loops in the reachability graphs so that a large portion of the computation time of service composition can be moved to a pre-processing unit; hence the response time is shortened during runtime. We also extended the WS-Pro to the ubiquitous computing area to improve fault-tolerance
Practical Complexity in Adapting Object Oriented Approach of Systems Analysis and Design
Recently, there has been a surge of interest in adapting object-oriented (OO) concepts, UML, and Unified Process of system development in the Systems Analysis and Design texts. However, there is a question of how to best fit these concepts with the existing coherent discussion of structured approach. This paper addresses some of the intricacies of OO concepts such as complexity of diagrams and models, weak links between phases, and lack of support for designing system components. We would like to recommend that there should be a separate text for the OO methodology and it should not present various OO models according to the phases of the traditional structured approach, rather it should focus on the evolution of the models leading to the design of system components. Furthermore, there should be a standard set of models for the OO methodology as well as a clear definition of steps as an analyst moves from one set of models to the next
Language Design for Reactive Systems: On Modal Models, Time, and Object Orientation in Lingua Franca and SCCharts
Reactive systems play a crucial role in the embedded domain. They continuously interact with their environment, handle concurrent operations, and are commonly expected to provide deterministic behavior to enable application in safety-critical systems. In this context, language design is a key aspect, since carefully tailored language constructs can aid in addressing the challenges faced in this domain, as illustrated by the various concurrency models that prevent the known pitfalls of regular threads. Today, many languages exist in this domain and often provide unique characteristics that make them specifically fit for certain use cases. This thesis evolves around two distinctive languages: the actor-oriented polyglot coordination language Lingua Franca and the synchronous statecharts dialect SCCharts. While they take different approaches in providing reactive modeling capabilities, they share clear similarities in their semantics and complement each other in design principles. This thesis analyzes and compares key design aspects in the context of these two languages. For three particularly relevant concepts, it provides and evaluates lean and seamless language extensions that are carefully aligned with the fundamental principles of the underlying language. Specifically, Lingua Franca is extended toward coordinating modal behavior, while SCCharts receives a timed automaton notation with an efficient execution model using dynamic ticks and an extension toward the object-oriented modeling paradigm
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