Louis O. Hertzberger

VLAM-G: A Grid-based virtual laboratory

The Grid-based Virtual Laboratory AMsterdam (VLAM-G), provides a science portal for distributed analysis in applied scientific research. It offers scientists remote experiment control, data management facilities and access to distributed resources by providing cross-institutional integration of information and resources in a familiar environment. The main goal is to provide a unique integration of existing standards and software packages. This paper describes the design and prototype implementation of the VLAM-G platform. In this testbed we applied several recent technologies such as the Globus toolkit, enhanced federated database systems, and visualization and simulation techniques. Several domain specific case studies are described in some detail. Information management will be discussed separately in a forthcoming paper.

A dynamic load balancing system for parallel cluster computing

In this paper we discuss a new approach to dynamic load balancing of parallel jobs in clusters of workstations and describe the implementation into a Unix run-time environment. The efficiency of the proposed methodology is shown by means of a number of case studies.

Virtual Enterprises and Federated Information Sharing

In general, a Virtual Enterprise (VE) is an interoperable network of pre-existing enterprises with a common goal, where the enterprises can function together as a single organization. With the objective of developing a reference architecture and a support infrastructure for VEs, the Esprit project PRODNET II (Production Planning and Management in an Extended Enterprise) is conceived. In the PRODNET architecture, the Distributed Information Management System (DIMS) component supports the VE information management requirements and provides a framework to exchange and cooperatively manage data between VE-member enterprises, while preserving the autonomy of individual enterprises. The DIMS design is based on an object-oriented federated/distributed information management architecture, specifically tailored for the VE paradigm. The focus of this paper is on describing the design of the federated architecture of the DIMS component.

A Sensor Processing Model Incorporating Error Detection and Recovery

In this paper we address the problem of providing a sensor-system with the ability to detect measurement errors and to recover from these errors. We propose to equip every sensor module in the sensor system with active and latent tests which verify respectively possible environmental independent and environmental dependent sensor failures. The recovery strategy is based on rules that are local to the different sensor modules. We will show the applicability in an example.

WS-VLAM: towards a scalable workflow system on the grid

Large scale scientific applications require extensive support from middleware and frameworks that provide the capabilities for distributed execution in the Grid environment. In particular, one of the examples of such frameworks is a Grid-enabled workflow management system. In this paper we present WS-VLAM workflow management system, describe its current design and the developments targeting to support efficient and scalable execution of large workflow applications on the Grid.

The PRODNET cooperative information management for industrial virtual enterprises

When designing an IT platform aimed at supporting industrial virtual enterprises (VEs), certain issues related to information management requirements become especially challenging, such as the physical distribution of data, the enterprise autonomy and privacy enforcement, access rights to shared information, and data visibility levels, among others. In the ESPRIT project PRODNET II, a federated database architecture was designed and implemented as the base support framework to effectively manage these issues associated with the sharing and exchange of information in the VE environment. In this paper, first the general information management requirements identified for the VE network in the PRODNET II project are described, and then the challenging design issues behind the development of the components of the federated information management system are presented.

A low-cost pose-measuring system for robot calibration

To maintain robot accuracy, calibration equipment is needed. In this paper we present a self-calibrating measuring system based on a camera in the robot hand plus a known reference object in the robot workspace. A collection of images of the reference object is obtained. Using image-processing, image-recognition and photogrammetric techniques, the positions and orientations of the camera are computed. The essential geometrical and optical camera parameters can be derived from the redundancy in the measurements. From each image the positions of markers on the reference object are extracted and the individual markers are identified. The camera positions for all images plus the parameters of the camera are solved together in a non-linear least-squares fitting procedure. Experimental results for this low-cost measuring system are presented.

A hierarchical view on modeling the reliability of a DSRC link for ETC applications

For electronic payments, the communication link has to be reliable. Dedicated short-range communication (DSRC) is a proposed solution for the automatic debiting of vehicles in an electronic toll collection (ETC) system without disturbing the traffic flow. The requirements on the reliability of such a system are high, which implies that only large-scale simulations with a lot of detail are effective for analyzing occasional errors. In this paper, a hierarchical approach is worked out that allows such simulations of the communication link, with a 80% reduction of the computational effort compared to simulation with full detail.

VLAM-G: Interactive data driven workflow engine for Grid-enabled resources

Grid brings the power of many computers to scientists. However, the development of Grid-enabled applications requires knowledge about Grid infrastructure and low-level API to Grid services. In turn, workflow management systems provide a high-level environment for rapid prototyping of experimental computing systems. Coupling Grid and workflow paradigms is important for the scientific community: it makes the power of the Grid easily available to the end user. The paradigm of data driven workflow execution is one of the ways to enable distributed workflow on the Grid. The work presented in this paper is carried out in the context of the Virtual Laboratory for e-Science project. We present the VLAM-G workflow management system and its core component: the Run-Time System (RTS). The RTS is a dataflow driven workflow engine which utilizes Grid resources, hiding the complexity of the Grid from a scientist. Special attention is paid to the concept of dataflow and direct data streaming between distributed workflow components. We present the architecture and components of the RTS, describe the features of VLAM-G workflow execution, and evaluate the system by performance measurements and a real life use case.

A reference architecture for scientific virtual laboratories

Abstract Recent advances in the IT can be applied to properly support certain complex requirements in the scientific and engineering domains. In experimental sciences, for instance, researchers should be assisted with conducting their complex scientific experimentation and supporting their collaboration with other scientists. The main requirements identified in such domains include the management of large data sets, distributed collaboration support, and high-performance issues, among others. The virtual laboratory project initiated at the University of Amsterdam aims at the development of a hardware and software reference architecture, and an open, flexible, and configurable laboratory framework to enable scientists and engineers with working on their experimentation problems, while making optimum use of modern information technology approaches. This paper describes the current stage of design of a reference architecture for this scientific virtual laboratory, and focuses further on the cooperative information management component of this architecture, and exemplifying its application to experimentation domain of biology.