Agent Based Modeling and Simulation: An Informatics Perspective

The term computer simulation is related to the usage of a computational model in order to improve the understanding of a system's behavior and/or to evaluate strategies for its operation, in explanatory or predictive schemes. There are cases in which practical or ethical reasons make it impossible to realize direct observations: in these cases, the possibility of realizing 'in-machina' experiments may represent the only way to study, analyze and evaluate models of those realities. Different situations and systems are characterized by the presence of autonomous entities whose local behaviors (actions and interactions) determine the evolution of the overall system; agent-based models are particularly suited to support the definition of models of such systems, but also to support the design and implementation of simulators. Agent-Based models and Multi-Agent Systems (MAS) have been adopted to simulate very different kinds of complex systems, from the simulation of socio-economic systems to the elaboration of scenarios for logistics optimization, from biological systems to urban planning. This paper discusses the specific aspects of this approach to modeling and simulation from the perspective of Informatics, describing the typical elements of an agent-based simulation model and the relevant research.Multi-Agent Systems, Agent-Based Modeling and Simulation

Modeling Environmental Operative Elements in Agent-Based Pedestrian Simulation

Models for pedestrian simulation are employed on a day-to-day basis for supporting the design and planning of the built environment in normal and evacuation situations. One of the aspects that are least investigated in the community, probably because it is considered closer to technology transfer than to research, is the modelling of operational elements of the simulated environment. The present paper briefly describes an agent-based approach to the representation of operative elements of the environment with particular attention to the mechanisms of interaction between these active objects and pedestrians

TOWARD A PLATFORM FOR MULTI-LAYERED MULTI-AGENT SITUATED SYSTEM (MMASS)-BASED SIMULATIONS: FOCUSING ON FIELD DIFFUSION

The paper introduces some issues and related solutions adopted in order to realize the MMASS platform. This is a framework to specify and execute simulation applications based on the multilayered multi-agent situated system model (MMASS). MMASS is a model for multi-agent systems (MAS) situated in an environment whose structure is explicitly defined. The behavior and interaction models of MMASS agents are strongly related to the spatial structure of their environment. The MMASS model is the result of a long-term research that has its roots and motivations on application domains and problems that require spatial features to be considered. Our experiences with these problems have concerned the design of domain models and their implementations, according to the MAS approach for simulation purposes. This activity has revealed that currently available tools do not support the management of spatial features of agent environment and interaction mechanisms defined by the MMASS model and thus they are not suitable for our purposes. The paper focuses on the MMASS platform that aims to support the specification and development of applications (mainly, simulations) based on MMASS. Design issues and related solutions that have been adopted in order to manage those aspects that characterize the MMASS model will be shown. After a description of the conceptual model that underlies the MMASS platform and its general architecture, we will overview how the platform supports the specification of agent structured environment, behavior and interaction, and how it supports the execution of agent actions and interactions. Then we will describe issues and adopted solutions (both algorithmic and implementative ones) to manage at-a-distance interaction among MMASS agents

Lane Formation Beyond Intuition Towards an Automated Characterization of Lanes in Counter-flows

Pedestrian behavioural dynamics have been growingly investigated by means of (semi)automated computing techniques for almost two decades, exploiting advancements on computing power, sensor accuracy and availability, computer vision algorithms. This has led to a unique consensus on the existence of significant difference between unidirectional and bidirectional flows of pedestrians, where the phenomenon of lane formation seems to play a major role. The collective behaviour of lane formation emerges in condition of variable density and due to a self-organisation dynamic, for which pedestrians are induced to walk following preceding persons to avoid and minimize conflictual situations. Although the formation of lanes is a well-known phenomenon in this field of study, there is still a lack of methods offering the possibility to provide an (even semi-) automatic identification and a quantitative characterization. In this context, the paper proposes an unsupervised learning approach for an automatic detection of lanes in multi-directional pedestrian flows, based on the DBSCAN clustering algorithm. The reliability of the approach is evaluated through an inter-rater agreement test between the results achieved by a human coder and by the algorithm

Hematopoietic Stem Cell Transplantation for Adult Acute Lymphoblastic Leukaemia

The most recent clinical trials on adult acute lymphoid leukaemia (ALL) have shown complete remission and disease-free survival (DFS) rates of 80-85% and 30-40%, respectively (Annino, et al, Durrant, et al, Kantarjian, et al, Larson, et al, Ribera, et al, Rowe). Intensified consolidation, particularly with high-dose methotrexate and high-dose cytarabine, may be one of the reasons for the improved outcome in recent series (Bassan and Hoelzer, Hoelzer and Gokbuget, Kebriaei and Larson). In addition, risk-adapted and subtype-oriented therapy may have contributed to this better outcome. However, the long term outcome of adult patients is still dismal, with approximately one third of the cases only being cured. At present, therapeutic options include conventional chemotherapy (CHT), high dose therapy with autologous and, especially, allogeneic stem cells transplantation (SCT) and, for certain subsets, such as BCR-ABL1+ ALL, specific targeted therapy (Piccaluga, et al). Although SCT has been used in adult ALL for more than 20 years, its role remains controversial as demonstrated by conflicting results in various studies. Previous casecontrolled studies did not show that allogeneic SCT (alloSCT) provided any advantage over CHT (Horowitz, et al, Zhang, et al) while in some studies there was an advantage, but restricted to young adults (Oh, et al). The number of controlled published or ongoing trials is remarkably small and some of them did not include both standard-risk and high-risk patients. Thus, it is difficult to draw definitive conclusions from their results. In fact, while some authors did not report any differences between alloSCT and chemotherapy or autologous SCT (ASCT)(Gupta, et al, Labar, et al), others only found differences favouring allogeneic SCT in standard risk (Goldstone, et al) or high-risk ALL patients (Sebban, et al, Thiebaut, et al, Thomas, et al). In this chapter, the Authors reviewed data concerning alloSCT in adult ALL and discuss current controversial and possible perspectives