Daniele Gianni

Sharing and reusing cardiovascular anatomical models over the Web: a step towards the implementation of the virtual physiological human project.

Sharing and reusing anatomical models over the Web offers a significant opportunity to progress the investigation of cardiovascular diseases. However, the current sharing methodology suffers from the limitations of static model delivery (i.e. embedding static links to the models within Web pages) and of a disaggregated view of the model metadata produced by publications and cardiac simulations in isolation. In the context of euHeart—a research project targeting the description and representation of cardiovascular models for disease diagnosis and treatment purposes—we aim to overcome the above limitations with the introduction of euHeartDB, a Web-enabled database for anatomical models of the heart. The database implements a dynamic sharing methodology by managing data access and by tracing all applications. In addition to this, euHeartDB establishes a knowledge link with the physiome model repository by linking geometries to CellML models embedded in the simulation of cardiac behaviour. Furthermore, euHeartDB uses the exFormat—a preliminary version of the interoperable FieldML data format—to effectively promote reuse of anatomical models, and currently incorporates Continuum Mechanics, Image Analysis, Signal Processing and System Identification Graphical User Interface (CMGUI), a rendering engine, to provide three-dimensional graphical views of the models populating the database. Currently, euHeartDB stores 11 cardiac geometries developed within the euHeart project consortium.

A software architecture to ease the development of distributed simulation systems

The simulation of modern systems may require an amount of computational resources that might not be available on a single host. Distributed simulation (DS) provides an effective way to scale up for the increased computational requirements. However, using existing DS environments remains the main obstacle to the wide adoption of DS systems, because of their inherent complexity. This complexity can be quantitatively shown by the extra effort that the development of DS systems requires compared to the development of conventional local simulation (LS) systems. In this paper we introduce SimArch, a layered architecture that eases the development of DS systems by enabling simulation developers to effortlessly obtain a DS system or derive a DS system from the equivalent LS one. A reference model is used throughout the paper to illustrate the use of SimArch in the development of DS systems and to prove how the DS development effort is lowered down with respect to the use of a conventional DS environment.

jEQN a java-based language for the distributed simulation of queueing networks

The increasing pervasiveness of large scale networks is bringing distributed simulation (DS) to the reach of academic and business communities besides the traditional military ones. This gives academics and industry the advantage of using larger execution platforms and of reusing locally implemented simulation models as building blocks of much larger models. Developing a distributed simulator however requires learning how to use a given DS standard (such as HLA), that implies a non-negligible amount of effort. This paper addresses the problem of defining a language that can equivalently support the development of local or distributed simulators, making the use of the DS standard transparent. The HLA standard is dealt with, but the method can be extended to any other DS standard. The language (called jEQN) addresses the extended queueing network (EQN) domain, and thus it also includes primitives to facilitate the development of queueing network distributed simulators.

A SAAS-based automated framework to build and execute distributed simulations from SysML models

The development of complex systems requires the use of quantitative analysis techniques to allow a designtime evaluation of the system behavior. In this context, distributed simulation (DS) techniques can be effectively introduced to assess whether or not the system satisfies the user requirements. Unfortunately, the development of a DS requires the availability of an IT infrastructure that could not comply with time-to-market requirements and budget constraints. In this respect, this work introduces HLAcloud, a model-driven and cloud-based framework to support both the implementation of a DS system from a SysML specification of the system under study and its execution over a public cloud infrastructure. The proposed approach, which exploits the HLA (High Level Architecture) DS standard, is founded on the use of model transformation techniques to generate both the Java/HLA source code of the DS system and the scripts required to deploy and execute the HLA federation onto the PlanetLab cloud-based infrastructure.

A layered architecture for the model-driven development of distributed simulators

The development of a distributed simulator requires knowledge and skills that might be unavailable or difficult to acquire. Bringing model-driven approaches to the development of distributed simulators contributes to reduce both the need for specific skills and the development effort. To support this innovative development methodology, we introduce a layered simulation architecture named SimArch that allows to define simulation models that can be transparently transformed into simulation programs ready to be executed in a distributed (or local) mode. SimArch defines layers of services at increasing levels of abstraction on top of the execution environment, thus allowing developers to build distributed simulators without explicit knowledge about the execution environment (local/distributed) and the specific distributed simulation infrastructure (e.g., HLA). In order to show the effectiveness of the proposed approach, SimArch has been provided with an Extended Queueing Network (EQN) simulation language, which has been applied to the development of an example distributed simulator in the computer network domain.

Using CORBA to enhance HLA interoperability in distributed and web-­‐based simulation

In distributed simulation, various simulation programs, or else components of a given simulation program, interact as elements of a simulation-oriented distributed computation. The High Level Architecture (HLA) is a standardization effort that provides a general framework for promoting interoperability and reusability in the simulation field. When applied to distributed simulation HLA shows some drawbacks that limit the desired degree of interoperability and reusability. This paper proposes a CORBA-based approach to overcome such drawbacks and improve HLA capabilities. The paper also illustrates how to combine the use of HLA and CORBA for Web-based simulation, which is the extension of distributed simulation to Web-based network infrastructures.

A model-driven method for building distributed simulation systems from business process models

The analysis of modern business processes implemented as orchestration of software services demands for new approaches that explicitly take into account the inherent complexity and distribution characteristics of such processes. In this respect, Distributed Simulation (DS) offers a viable tool to cope with such a demand, due to the aggregation, scalability, representativeness and load balancing properties that it allows to achieve. However, the use of DS is mostly limited by the specialized technical know-how and the extra-development that DS requires with respect to approaches based on conventional local simulation. This paper proposes a model-driven method that enables the DS-based analysis of business processes by introducing the automated transformation of business process models into analysis models that are specified as Extended Queueing Network (EQN) models and executed as distributed simulations. The paper also presents an example application to a business process for an e-commerce scenario.

Bringing Discrete Event Simulation Concepts into Multi-agent Systems

Agent-based Modelling (ABM) is a very efficacious conceptualisation paradigm that easily allows the representation of very complex physical systemscomposed of autonomous, possibly intelligent, interacting entities. For this reason, Agent-based systems (ABS) have been incorporated into simulation as a mean of effectively increasing the realism through adaptation and learning abilities. The integration between ABM and simulation, namely Agent-based Modelling and Simulation (ABMS), however, can be further exploited bymodelling the simulation system as a Multi Agent System (MAS). To achieve this, the first step is to provide ABSs with discrete event simulation (DES)concepts (simulation time and services) and an interaction protocol.In this paper, we present a formulation of DES in terms of MAS through the design of software framework, named SimJADE, for the ABMS.

A Transformation Approach to Enact the Design-Time Simulation of BPMN Models

Simulation is a key technique for enabling business process analysts to predict the process behavior at design time. However, some issues limit the effectiveness of business process simulation (e.g., lack of simulation know how, costs and difficulties for gathering process data, semantic gap between the business process model and the simulation model). This paper proposes a model-driven method that automates the generation of executable business process simulation code. In order to address the increasing complexity and to take into account the inherent collaborative aspects of modern business processes, the simulation code produced by the proposed method replicates the business process distributed structure (in terms, e.g., of a service-oriented architecture) by including a set of simulation services that are orchestrated into a distributed simulation execution. The characterization of business processes in terms of the required performance properties is introduced through standard BPMN annotations according to a well-defined syntax, thus avoiding the need of additional languages. The implementation of the executable simulation code is based on the eBPMN language, a domain-specific language that preserves the semantic behavior of the original BPMN standard.

A MDA-based approach for the development of DEVS/SOA simulations

The intrinsic complexity of the DEVS formalism and the manual production of DEVS-based simulations might constitute obstacles to the adoption of DEVS for both system modelers and simulation users. To overcome these obstacles, this paper introduces a model-driven approach for the development of DEVS simulations. The approach provides modelers and users with standard graphical modeling languages and with model transformation specifications for automated code production. Specifically, the approach enables the UML specification of DEVS models and automates the generation of DEVS simulations that make use of the DEVS/SOA implementation. An example application to the production of a DEVS/SOA simulation for a basic queuing system is also presented, to show the details of the proposed approach.