There are at least two major security challenges in mobile code distributedsystems. First hosts have to be protected from potentially malicious actions of mobile code they are executing. Many techniques are known whi...
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There are at least two major security challenges in mobile code distributedsystems. First hosts have to be protected from potentially malicious actions of mobile code they are executing. Many techniques are known which address this problem. Second mobile agents themselves have to be protected against malicious hosts. Satisfactory ways to deal with the second problem are necessary features for many of the (security-sensitive) tasks mobile agent (MA) systems.are envisioned for, e.g., in e-commerce applications where a shopping agent is sent out on the Internet, vendors have a high incentive in tampering with these agents. The key point is is that the originator of the agent needs to have sound guarantees that the results an agent brings back are correct. Why else should he send out the agent in the first place?.
Online analytical processing techniques are used for data analysis and decision support systems. The multidimensionality of the underlying data is well represented by multidimensional databases. For data mining in kno...
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Online analytical processing techniques are used for data analysis and decision support systems. The multidimensionality of the underlying data is well represented by multidimensional databases. For data mining in knowledge discovery, OLAP calculations can be effectively used. For these, high performance parallel systems.are required to provide interactive analysis. Precomputed aggregate calculations in a data cube can provide efficient query processing for OLAP applications. We present parallel data cube construction on distributed-memory parallel computers from a relational database. The data cube is used for data mining of associations using attribute focusing. Results are presented for these on the IBM-SP2, which show that our algorithms and techniques are scalable to a large number of processors, providing a high performance platform for such applications.
The confluence of computers, communications, and databases is quickly creating a global virtual database where many applications require real time access to both temporally accurate and multimedia data. This is partic...
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The confluence of computers, communications, and databases is quickly creating a global virtual database where many applications require real time access to both temporally accurate and multimedia data. This is particularly true in military and intelligence applications, but these required features are needed in many commercial applications as well. We are developing a distributeddatabase, called BeeHive, which could offer features along different types of requirements: real time, fault tolerance, security, and quality of service for audio and video. Support of these features and potential trade offs between them could provide a significant improvement in performance and functionality over current distributeddatabase and object management systems. We present a high level design for BeeHive architecture and sketch the design of the BeeHive Object Model (BOM) which extends object oriented data models by incorporating time and other features into objects.
The present state of communication networks with respect to speed and reliability and the recent growth of distributed applications have created a need for a global enterprise solution to the legality checking and att...
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The present state of communication networks with respect to speed and reliability and the recent growth of distributed applications have created a need for a global enterprise solution to the legality checking and attribute evaluation requirement. Traditionally, the mainframe systems.provided the cohesion of all the processes with respect to the company regulations. When decentralized systems.and applications became widely used the legality checking mechanism lost its central role and became a necessary component for every decentralized system. In this paper a methodology to reconnect these systems.with respect to their legality checking and attribute evaluation needs is presented. A generic Legality Checking system has been developed and integrated with scheduling systems.of the airline domain. It is shown that the client-server model adopted can bring back in a flexible manner the lost homogeneity of the central legacy systems.
Computer supported cooperative work (CSCW) has the potential of providing the environment needed for groups of diverse users to cooperate in real-time to achieve their common goals. This potential has been under-utili...
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Computer supported cooperative work (CSCW) has the potential of providing the environment needed for groups of diverse users to cooperate in real-time to achieve their common goals. This potential has been under-utilized due to the lack of cooperation between CSCW systems.and the underlying network services to accommodate the dynamic behavior and varying quality-of-service (QoS) requirements of CSCW groups and the applications they use. To satisfy such requirements, QoS multicast routing should be employed. Unfortunately, current multicast services are inadequate for the traffic generated in CSCW environments. The authors present a CSCW-specific routing architecture that supports QoS requirements and is both scalable and robust. Scalability is needed to accommodate a large number of multicast groups and highly dynamic group membership and behavior, while robustness provides reliability and stable performance for each group during adaptation and in presence of the other existing groups. In the architecture, a router QoS manager, on behalf of a multicast routing manager, negotiates with host and CSCW-specific QoS managers for efficient resource utilization and guaranteed QoS delivery. The multicast routing manager switches between routing trees and algorithms as warranted by the changes in the characteristics and requirements of the CSCW systems.running at the hosts. They present a class-based and a partial view-based method to scalability. They also present a centralized and a distributed method to establishing a group's QoS multicast path while providing robustness.
We present a technique that uses coverage measures in reliability estimation for fault tolerant programs, particularly N-version software. This technique exploits both coverage and time measures collected during testi...
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ISBN:
(纸本)0818681780
We present a technique that uses coverage measures in reliability estimation for fault tolerant programs, particularly N-version software. This technique exploits both coverage and time measures collected during testing phases for the individual program versions and the N-version software system for reliability prediction. The application of this technique on the single-version software was presented in our previous research. In this paper we Extend this technique and apply it on the N-version programs. The results obtained from the experiment conducted on an industrial project demonstrate that our technique significantly reduces the hazard of reliability overestimation for both single-version and multi-version fault tolerant softwaresystems.
NTT software Labs is producing a distributed, self-configuring information navigation infrastructure designed to scale to global proportions. For reasons of large scale, unreliability (of the Internet, its connected c...
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NTT software Labs is producing a distributed, self-configuring information navigation infrastructure designed to scale to global proportions. For reasons of large scale, unreliability (of the Internet, its connected computers, and the implementations), and the complete autonomy of the participants, a number of difficult database and cache consistency problems arise that are not solved by techniques commonly used either for the Internet (i.e. DNS), or for existing distributeddatabasesystems. This paper describes a set of strategies designed to solve these problems. In particular, it focuses on the use of third-party detection and notification of database and cache inconsistency.
Three algorithms designed to enforce different quality of service criteria are presented, as well as empirical assessments of the algorithms for three large industrial telecommunications systems. These assessments are...
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Three algorithms designed to enforce different quality of service criteria are presented, as well as empirical assessments of the algorithms for three large industrial telecommunications systems. These assessments are made in terms of the simulated performance of each system on average loads selected from operational distributions collected during beta release and field use. In addition, synthetic heavy loads designed to cause the overall CPU utilization rates to exceed 90% of capacity were run. The algorithms build on previously defined load testing algorithms, and use parameters and operational distributions computed for that purpose. This makes the quality of service enforcement algorithms particularly efficient. The primary bases for the assessment of the algorithms were the overall deviation of the response time from the average, and the fraction of service requests that were throttled from clients under varying conditions.
Fault tolerance is a survival attribute of complex computer systems.and software in their ability to deliver continuous service to their users in the presence of faults. Formulating an analytic model for dependability...
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ISBN:
(纸本)0818682132
Fault tolerance is a survival attribute of complex computer systems.and software in their ability to deliver continuous service to their users in the presence of faults. Formulating an analytic model for dependability and performance evaluation of hardware/software fault tolerant architectures can be quite cumbersome. Also, in practice, isolating the effect of various parameters on a system, while holding the others constant requires exploring a variety of scenarios. It is economically infeasible to build several such systems. Simulation offers an attractive mechanism for dependability evaluation and the study of the influence of various parameters on the failure behavior of the system. In this paper, we develop algorithms to simulate the failure behavior of three commonly used fault tolerant architectures, viz., distributed Recovery Block (DRB), N-Version Programming (NVP) and N-Self Checking Programming (NSCP). We demonstrate the ability of the approach to simulate complex failure scenarios with various dependencies using some illustrative numerical examples.
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