A graph-based aspect interference detection approach for UML-based aspect-oriented models

Aspect Oriented Modeling (AOM) techniques facilitate separate modeling of concerns and allow for a more flexible composition of these than traditional modeling technique. While this improves the understandability of each submodel, in order to reason about the behavior of the composed system and to detect conflicts among submodels, automated tool support is required. Current techniques for conflict detection among aspects generally have at least one of the following weaknesses. They require to manually model the abstract semantics for each system; or they derive the system semantics from code assuming one specific aspect-oriented language. Defining an extra semantics model for verification bears the risk of inconsistencies between the actual and the verified design; verifying only at implementation level hinders fixng errors in earlier phases. We propose a technique for fully automatic detection of conflicts between aspects at the model level; more specifically, our approach works on UML models with an extension for modeling pointcuts and advice. As back-end we use a graph-based model checker, for which we have defined an operational semantics of UML diagrams, pointcuts and advice. In order to simulate the system, we automatically derive a graph model from the diagrams. The result is another graph, which represents all possible program executions, and which can be verified against a declarative specification of invariants.\ud To demonstrate our approach, we discuss a UML-based AOM model of the "Crisis Management System" and a possible design and evolution scenario. The complexity of the system makes con°icts among composed aspects hard to detect: already in the case of two simulated aspects, the state space contains 623 di®erent states and 9 different execution paths. Nevertheless, in case the right pruning methods are used, the state-space only grows linearly with the number of aspects; therefore, the automatic analysis scales

From Social Simulation to Integrative System Design

As the recent financial crisis showed, today there is a strong need to gain "ecological perspective" of all relevant interactions in socio-economic-techno-environmental systems. For this, we suggested to set-up a network of Centers for integrative systems design, which shall be able to run all potentially relevant scenarios, identify causality chains, explore feedback and cascading effects for a number of model variants, and determine the reliability of their implications (given the validity of the underlying models). They will be able to detect possible negative side effect of policy decisions, before they occur. The Centers belonging to this network of Integrative Systems Design Centers would be focused on a particular field, but they would be part of an attempt to eventually cover all relevant areas of society and economy and integrate them within a "Living Earth Simulator". The results of all research activities of such Centers would be turned into informative input for political Decision Arenas. For example, Crisis Observatories (for financial instabilities, shortages of resources, environmental change, conflict, spreading of diseases, etc.) would be connected with such Decision Arenas for the purpose of visualization, in order to make complex interdependencies understandable to scientists, decision-makers, and the general public.Comment: 34 pages, Visioneer White Paper, see http://www.visioneer.ethz.c

Some Remarks about the Complexity of Epidemics Management

Recent outbreaks of Ebola, H1N1 and other infectious diseases have shown that the assumptions underlying the established theory of epidemics management are too idealistic. For an improvement of procedures and organizations involved in fighting epidemics, extended models of epidemics management are required. The necessary extensions consist in a representation of the management loop and the potential frictions influencing the loop. The effects of the non-deterministic frictions can be taken into account by including the measures of robustness and risk in the assessment of management options. Thus, besides of the increased structural complexity resulting from the model extensions, the computational complexity of the task of epidemics management - interpreted as an optimization problem - is increased as well. This is a serious obstacle for analyzing the model and may require an additional pre-processing enabling a simplification of the analysis process. The paper closes with an outlook discussing some forthcoming problems

Evaluating health information system projects using analytical and modeling methods

In recent years the value of the use of evaluation methods in all aspects of economic sectors, including the field of health care, has been increasingly recognized. The thrust of this paper is to explore the potential use of a) Cost-Benefit Analysis and b) Simulation and Modeling methods in estimating the value of Health Information System (HIS) projects. These methods were chosen for consideration as the most appropriate, primarily because CBA can measure delivered value of HIS interventions by weighting cost and benefits and identifying what is more socially desirable, while Simulation and Modeling tools can be used to estimate the future value of health care changes concerning HIS. The paper discusses these two families of methods, their evaluation potential is analyzed, and arguments for and against the use of each method are presented. Finally, methodological considerations and limitations are discussed and areas for future research are suggested

Urban Simulation Models: Contributions as Analysis-Methodology in a Project of Urban Renewal

The recent urban transformations produced in cities indicate the need to propose new theoretical and methodological approaches in physical planning. Based on the idea of complexity, it is required to integrate, in the analysis, multiplicity of interrelated factors involved in urban development,moreover, to develop planning tools that can incorporate variables not initially considered (for example when the norms were sanctioned) and instruments that would provide assessment alternatives to planning decisions in real time. The simulation models are suggested as tools to detect the elements, relationships and the dynamics in a simplified form that allow experiencing on the results. That is to say, a theoretical position on to a computer model is translated to investigate (in an experimental way) possible solutions derived from manipulating the variables, before the phenomenon is materialized. In the case of urban planning, this condition is of particular relevance, given the importance to anticipate unwanted effects in the intervention context that may arise when urban projects are built. The paper evaluates the application of a simulation methodology,based on the dynamics of systems and the application of software that can anticipate the effects of certain decisions in an urban renewal project in the city of Córdoba, Argentina. It applies the General Systems Theory that is a contribution to the notion of complex thought and is trans-disciplinary. Based on the idea of complex and multidimensional city, the effects of a real estate development are analyzed and conclusions on the limits and possibilities of using this tool during the processes of urban management are provided.Fil: Marengo, Maria Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño. Instituto de Investigación de la Vivienda; Argentin

Exploring agent-based methods for the analysis of payment systems: a crisis model for StarLogo TNG

agent-based modeling, payment systems, RTGS, liquidity, crisis simulation Abstract: This paper presents an exploratory agent-based model of a real time gross settlement (RTGS) payment system. Banks are represented as agents who exchange payment requests, which are settled according to a set of simple rules. The model features the main elements of a real-life system, including a central bank acting as liquidity provider, and a simplified money market. A simulation exercise using synthetic data of BI-REL (the Italian RTGS) predicts the macroscopic impact of a disruptive event on the flow of interbank payments. The main advantage of agent - based modeling is that we can dynamically see what happens to the major variables involved. In our reduced-scale system, three hypothetical distinct phases emerge after the disruptive event: 1) a liquidity sink effect is generated and the participants’ liquidity expectations turn out to be excessive; 2) an illusory thickening of the money market follows, along with increased payment delays; and, finally 3) defaulted obligations dramatically rise. The banks cannot staunch the losses accruing on defaults, even after they become fully aware of the critical event, and a scenario emerges in which it might be necessary for the central bank to step in as liquidity provider. The methodology presented differs from traditional payment systems simulations featuring deterministic streams of payments dealt with in a centralized manner with static behavior on the part of banks. The paper is within a recent stream of empirical research that attempts to model RTGS with agent – based techniques.