1,721,181 research outputs found
A Fault Tolerance Access to Legacy Database Systems using CORBA Technology
No full textThis work presents a software-implemented fault tolerance approach for building a reliable database application in a CORBA environment. Database applications have functional requirements and non-functional requirements, such as dependability and performance. We provide an architectural framework that makes it possible to separately address these issues. More precisely, it is possible to: i) guarantee functional properties by incorporating existing software modules, and ii) add dependability to the resulting system via proper programming of the business logic of the Middle Tier. The legacy software is integrated in the new system with no changes. This strategy can effectively reduce the development effort for building a reliable system, while protecting the investment in legacy application
Improving the QoS of MPEG2 Streaming over Wireless LANs
No full textWe propose a simulation-based approach to quality-of-service (QoS) improvement of multimedia streaming over wireless LANs. Since multimedia applications have stringent real time constraints, transmission schemes which rely on massive use of redundancy are not viable options. We present a portable simulation framework consisting of re-configurable software components. We build a simulation model which reflects the peculiarities of the MPEG-2 coding technique and streaming process by specializing the objects of the framework. We propose a set of strategies, which improve the QoS of the transmission, while limiting the amount of redundancy used. Finally, we conduct a quality and cost analysis of the proposed alternatives via detailed simulation of a case study system
Building a dependable system from a legacy application with CORBA
No full textThis paper presents a dependability oriented, fault tolerance based system design, development, and deployment approach. The approach relies on an architectural framework, which allows legacy software modules to be reused as the basic building blocks of a distributed dependable application. Different levels of replication and alternative adjudication strategies are implemented behind a unified interface. These can be configured for achieving the optimal compromise between dependability and performance, according to application, deployment environment, and fault characteristics. The suggested solution can be implemented on top of any CORBA infrastructure. The architecture has been developed and tested. Experimental results are presented and discussed
An Architecture for Security Oriented Perfective Maintenance of Legacy Software
No full textThis work presents an implementation strategy which exploits the separation of concerns and reuse in a multi-tier architecture to improve the security (availability, integrity, and confidentiality) level of an existing application. Functional properties are guaranteed via wrapping of the existing software modules. Security mechanisms are handled by the business logic of the middle-tier: availability and integrity are achieved via replication of the functional modules and the confidentiality is obtained via cryptography. The technique is presented with regard to a case study application. We believe that our experience can be used as a guideline for software practitioners to solve similar problems. We thus describe the conceptual model behind the architecture, discuss implementation issues, and present technical solutions
La ‘carcerazione di massa’ a Roma tra fine monarchia e gli inizi della repubblica
No full textThe paper focuses on the use of lautumiae in Ancient Rome. These sites were stone quarries from which the building materials for the construction of the city were extracted, and the oldest among them date back to the end of the Etruscan monarchy. In Varro's definition these places are described as prisons. The research connects the extractive use of the lautumiae with the needs of containment of the Romans. In fact, some caves when the mining material was exhausted, were reused as mass imprisonment camps
Proceedings of the 27th IEEE International Symposium on Reliable Distributed Systems, SRDS 2008: Message from the general chair
No full text“Architecture and FPGA Implementation of a Digit-Serial RSA Processor”
No full textthis paper we present an innovative hardware architecture and an FPGA-based implementation of the Montgomery's algorithm based on a digit-serial approach, which allows the basic arithmetic operations to be broken into words and processed in a serialized fashion. As a consequence, the architecture implementation takes advantage of a short critical path and low area requirements. In fact, as compared to other solutions in the literature, the proposed implementation of the RSA processor has smaller area requirements and comparable performance. The serialization factor S of our serial architecture is taken as a parameter and the final performance level is given as a function of this factor. We thoroughly explore the design tradeo#s, in terms of area requirements vs time performance, for di#erent values of the key length and the serialization facto
The Logarithmic Utility Functions of the Partially Informed Agents
No full textIn [7] we extend the asset pricing framework introduced by Guasoni [3] to the case of n +
1 Brownian motions and two agents: ”informed agent” and ”partially informed agent”. In this paper we
examine a model of a financial market with n Brownian motions and four agents: informed agent with access
to all information, uninformed agent with access to minimum information, and two partially informed
agents with access to partial information that are not necessarily comparable to each other. We examine the
information of each agents using Hitsuda representation [4]. In theorem 21 we compare the logarithmic
utility functions of the agents. The present framework can be extended to the case with further partially
informed agents. For both cases the results for the logarithmic utility functions are similar
Asimmetria informativa in un mercato con n+1 moti browniani
No full textQuesto lavoro esamina l’asimmetria informativa nei mercati finanziari
applicabile anche ad una micro prospettiva. In particolare, ci proponiamo
di estendere il lavoro sull’asset pricing introdotto da Guasoni (2006),
il quale analizza le dinamiche dei prezzi che presentano sia una componente martingala, descritta da shocks permanenti, e una componente stazionaria, descritta da shocks temporanei. Inizialmente, deriviamo una generalizzazione di questo modello sull’asset pricing, utilizzando n moti Browniani, prevedendo come (n + 1)th elemento un processo OrnsteinUhlenbeck.
Otteniamo una dinamica non Markoviana per gli agenti non
informati, mettendo in tal modo in discussione la validità delle ipotesi di
mercato efficiente. Inoltre, confrontiamo le posizioni degli agenti informati con quelle degli agenti non informati. In questo quadro, la filtrazione per gli agenti informati è più grande e inizialmente assegnata, mentre la filtrazione per gli agenti non informati è più piccola e ottenuta attraverso la rappresentazione di Hitsuda (1968). Per entrambi gli agenti, nell’ambito del problema della massimizzazione dell’utilità logaritmica, i nostri studi forniscono risultati simili a quelli ottenuti da Guasoni
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