System mechanisms for partial rollback of mobile agent execution

Mobile agent technology has been proposed for various fault-sensitive application areas, including electronic commerce, systems management and active messaging. Recently proposed protocols providing the exactly-once execution of mobile agents allow the usage of mobile agents in these application areas. Based on these protocols, a mechanism for the application-initiated partial rollback of the agent execution is presented in this paper. The rollback mechanism uses compensating operations to roll back the effects of the agent execution on the resources and uses a mixture of physical logging and compensating operations to rollback the state of the agent. The introduction of different types of compensating operations and the integration of an itinerary concept with the rollback mechanism allows performance improvements during the agent rollback as well as during the normal agent execution

A protocol for preserving the exactly-once property of mobile agents

Mobile agents are autonomous objects that can migrate from node to node of a computer network. Mobile agent technology has been proposed for various application areas, including electronic commerce, systems management and active messaging. Many of these applications - especially those for electronic commerce - require agents to be performed 'exactly once', independent of communication and node failures. In other words, once a mobile agent has been launched, it must never be lost before its execution is finished. Moreover, each 'portion' of the agent performed at the visited nodes is performed exactly once. Due to the autonomy of mobile agents, there is no 'natural' instance that monitors the progress of an agent's execution. As a result of that agents may be blocked due to node crashes or network partitioning even if there are other nodes available that could continue processing. In this paper, we will describe a protocol that ensures the exactly once property of agents and additionally reduces the blocking probability of agents by introducing so-called observer nodes for monitoring the progress of agents. This protocol is based on conventional transactional technology, such as defined by X/Open DTP or CORBA OTS. It is implemented in the Mole, a mobile agent system developed at Stuttgart University

AIDA I - Abschlußbericht

In diesem Bericht geht es um die Zusammenfassung der Erkenntnisse, die im Verlauf der ersten Phase des AIDA-Projektes bis September 1997 gewonnen wurden. AIDA ist ein Projekt, das von der Deutschen Forschungsgemeinschaft (DFG) finanziert wird. Das Thema dieses Projektes sind mobile Agenten, also Einheiten, die aus Code, Daten und Zustand bestehen und sich selbständig in einem Netzwerk bewegen können. Das Ziel von AIDA I war es, auf der Grundlage eines allgemeinen Verarbeitungsmodells flexible Systemmechanismen für verteilte, agentenbasierte Systeme zu entwickeln

ATOMAS : a transaction-oriented open multi agent system; final report

The electronic marketplace of the future will consist of a large number of services located on an open, distributed and heterogeneous platform, which will be used by an even larger number of clients. Mobile Agent Systems are considered to be a precondition for the evolution of such an electronic market. They can provide a flexible infrastructure for this market, i.e. for the installation of new services by service agents as well as for the utilization of these services by client agents. Mobile Agent Systems basically consist of a number of locations and agents. Locations are (logical) abstractions for (physical) hosts in a computer network. The network of locations serves as a unique and homogeneous platform, while the underlying network of hosts may be heterogeneous and widely distributed. Locations therefore have to guarantee independence from the underlying hard- and software. To make the Mobile Agent System an open platform, the system furthermore has to guarantee security of hosts against malicious attacks

Analysis of distribution schemes for the management of location information

New applications in the area of mobile computing make heavy use of knowledge about the application's run-time environment. Applications running on mobile devices in particular exploit knowledge about their current geographical position or query for the location of other interesting objects. To manage such queries some applications provide a location service specifically tailored for their needs. The efficient and application-independent handling of such queries calls for a global and universal location service. Considering a large number of users and queries to be handled, a distributed implementation of a location service is necessary. This paper analyses three schemes for the partitioning of location information and derives a performance model for these partitioning schemes. Finally, an example for the application of the analysis' results is presented for a universal location service within the Nexus system, an infrastructure for location aware mobile computing

Chemosensory properties of murine nasal and cutaneous trigeminal neurons identified by viral tracing

BACKGROUND: Somatosensation of the mammalian head is mainly mediated by the trigeminal nerve that provides innervation of diverse tissues like the face skin, the conjunctiva of the eyes, blood vessels and the mucouse membranes of the oral and nasal cavities. Trigeminal perception encompasses thermosensation, touch, and pain. Trigeminal chemosensation from the nasal epithelia mainly evokes stinging, burning, or pungent sensations. In vitro characterization of trigeminal primary sensory neurons derives largely from analysis of complete neuronal populations prepared from sensory ganglia. Thus, functional properties of primary trigeminal afferents depending on the area of innervation remain largely unclear. RESULTS: We established a PrV based tracing technique to identify nasal and cutaneous trigeminal neurons in vitro. This approach allowed analysis and comparison of identified primary afferents by means of electrophysiological and imaging measurement techniques. Neurons were challenged with several agonists that were reported to exhibit specificity for known receptors, including TRP channels and purinergic receptors. In addition, TTX sensitivity of sodium currents and IB4 binding was investigated. Compared with cutaneous neurons, a larger fraction of nasal trigeminal neurons showed sensitivity for menthol and capsaicin. These findings pointed to TRPM8 and TRPV1 receptor protein expression largely in nasal neurons whereas for cutaneous neurons these receptors are present only in a smaller fraction. The majority of nasal neurons lacked P2X(3 )receptor-mediated currents but showed P2X(2)-mediated responses when stimulated with ATP. Interestingly, cutaneous neurons revealed largely TTX resistant sodium currents. A significantly higher fraction of nasal and cutaneous afferents showed IB4 binding when compared to randomly chosen trigeminal neurons. CONCLUSION: In conclusion, the usability of PrV mediated tracing of primary afferents was demonstrated. Using this technique it could be shown that compared with neurons innervating the skin nasal trigeminal neurons reveal pronounced chemosensitivity for TRPM8 and TRPV1 channel agonists and only partially meet properties typical for nociceptors. In contrast to P2X(3 )receptors, TRPM8 and TRPV1 receptors seem to be of pronounced physiological relevance for intranasal trigeminal sensation

AIDA II - Abschlußbericht

In diesem Bericht geht es um die Zusammenfassung der Erkenntnisse, die im Verlauf der zweiten Phase des AIDA-Projektes von März 1998 bis Februar 2000 gewonnen wurden. AIDA ist ein Projekt, das von der Deutschen Forschungsgemeinschaft (DFG) finanziert wird. Das Thema dieses Projektes sind Systemmechanismen zur Unterstützung mobiler Agenten, also Einheiten, die aus Code, Daten und Zustand bestehen und sich selbstständig in einem Netzwerk bewegen können. Die Ziele von AIDA II waren die Erarbeitung des Themenbereichs Sicherheit in Mobile-Agenten-Systemen mit Schwerpunkt auf der Sicherheit mobiler Agenten gegenüber böswilligen Hosts, die Implementierung von Terminierungsprotokollen und Waisenerkennungsmechanismen, Abrechnungsmechanismen und schließlich Mechanismen zur Strukturunterstützung für Agentenanwendungen

Autonomic dysfunction in epilepsy mouse models with implications for SUDEP research

Epilepsy has a high prevalence and can severely impair quality of life and increase the risk of premature death. Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in drug-resistant epilepsy and most often results from respiratory and cardiac impairments due to brainstem dysfunction. Epileptic activity can spread widely, influencing neuronal activity in regions outside the epileptic network. The brainstem controls cardiorespiratory activity and arousal and reciprocally connects to cortical, diencephalic, and spinal cord areas. Epileptic activity can propagate trans-synaptically or via spreading depression (SD) to alter brainstem functions and cause cardiorespiratory dysfunction. The mechanisms by which seizures propagate to or otherwise impair brainstem function and trigger the cascading effects that cause SUDEP are poorly understood. We review insights from mouse models combined with new techniques to understand the pathophysiology of epilepsy and SUDEP. These techniques include in vivo, ex vivo, invasive and non-invasive methods in anesthetized and awake mice. Optogenetics combined with electrophysiological and optical manipulation and recording methods offer unique opportunities to study neuronal mechanisms under normal conditions, during and after non-fatal seizures, and in SUDEP. These combined approaches can advance our understanding of brainstem pathophysiology associated with seizures and SUDEP and may suggest strategies to prevent SUDEP

Nexus - an open global infrastructure for spatial-aware applications

Due to the lack of a generic platform for location- and spatial-aware systems, many basic services have to be reimplemented in each application that uses spatial-awareness. A cooperation among different applications is also difficult to achieve without a common platform. In this paper we present a platform that solves these problems. It provides an infrastructure that is based on computer models of regions of the physical world, which are augmented by virtual objects. We show how virtual objects make the integration of existing information systems and services in spatial-aware systems easier. Furthermore, our platform supports interactions between the computer models and the real world and integrates single models in a global 'Augmented World'