Structured knowledge is the most important component of semantic based information systems required to automate intelligent tasks which are normally performed by expert humans. The knowledge about a domain is typicall...
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Structured knowledge is the most important component of semantic based information systems required to automate intelligent tasks which are normally performed by expert humans. The knowledge about a domain is typically structured in the form of ontologies. An ontology organizes basic terms and the rules for combining these terms in the form that is machine-interpretable and machine-understandable. Therefore, defining an ontology should be considered an important and serious task with well-defined tools and techniques to verify and validate it. A considerable work is being done to define the processes to develop Ontologies for every phase of its life-cycle [1]. Automated tools to evaluate the contents of an ontology are a great help for large scale ontology developers. We formulated some ontologies to represent real life situations and left certain errors in those ontologies intentionally to see whether these tools would raise the alarm or not. To our surprise, there were some important situations where the alarm should have been raised, but we did not get any warning. In this paper, we report those situations and present algorithms to raise the alarm. We have surveyed the available literature with reference to these situations, and unfortunately could not found satisfactory answer. This paper also summarizes the survey. One of the most difficult situation to detect with automated tools is the incompleteness. This requires the intervention of the domain experts / ontology developers. We discovered that disjoint knowledge and exhaustive knowledge omissions are not being handled by existing tools to raise an alarm for the developers. Algorithms have been proposed to tackle these situations. These algorithms have been executed on a number of case studies. We found them working properly.
Recently, there is a growing trend towards the use of multimedia in software systems for different purposes and safety critical systems are no exception to this. But reliability of safety critical systems is a serious...
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Recently, there is a growing trend towards the use of multimedia in software systems for different purposes and safety critical systems are no exception to this. But reliability of safety critical systems is a serious concern. Formal methods have proven their worth in enhancing the reliability of the software in this regard. Z specification language is one such widely used formal specification language. But unfortunately Z language has not been used yet to specify multimedia contents. The integration of multimedia content in safety critical systems has necessitated the multimedia extensions in Z language. In this paper, we explored the opportunity of using formal methods for multimedia systems. We had also specified some of the multimedia contents in Z specification language.
Mobility management in a fast moving environment is convoluted by issues like speed of movement, detection of movement, handoff processing and scarcity of media resources. Most of the proposed architectures and soluti...
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Mobility management in a fast moving environment is convoluted by issues like speed of movement, detection of movement, handoff processing and scarcity of media resources. Most of the proposed architectures and solutions for mobility management use complex processing to reduce handoff latencies. In this paper a light-weight fast mobility management scheme is proposed which is based on strategic deployment of wireless LAN (WLAN) hotspots in a hierarchy of overlapped components like handoff anchor points (HAP), access routers (ARs) and access points (APs). The major handoff decision is taken in the HAP, a novel component in proposed architecture, which last for a significantly longer time due to reduced chances in probable moving path and by sending early binding updates through active ARs. Handoff latency has been reduced to almost link layer handoff time with a high level of predictability and reliability. Simulation results highlight improvements achieved in throughput, scalability, and handoff latencies.
Data-intensive scientific and engineering applications require both transfers of large amounts of data between storage systems and access to large amounts of data (gigabytes or tera bytes) by many geographically distr...
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Data-intensive scientific and engineering applications require both transfers of large amounts of data between storage systems and access to large amounts of data (gigabytes or tera bytes) by many geographically distributed applications. There are already a number of storage systems in use by the grid community, each of which was designed to satisfy specific requirements for storing, transferring and accessing large datasets. Unfortunately, most of these storage systems utilize incompatible and often unpublished protocols for accessing data and therefore use their own client libraries to access data. To overcome these incompatibilities in protocols, different point-to-point, and point-to-multipoint replication architectures based on UDP and/or TCP have been proposed like GridFTP (Allcock, 2003), FPFR (Izmailov et al.), BUDP (He et al., 2002), FTCP (Jin et al., 2004) etc. We have proposed a similar replication scheme called RHUT trying to combine the strengths of these protocols in an optimum way and eliminating their anomalies. This paper presents the architecture of RHUT in detail from an implementation point of view
Transmission control protocol (TCP) provides reliable end-to-end data communication under unpredictable and dynamic network conditions. Different variants of TCP have been proposed which show varying degree of resilie...
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Transmission control protocol (TCP) provides reliable end-to-end data communication under unpredictable and dynamic network conditions. Different variants of TCP have been proposed which show varying degree of resilience in best effort IP networks characteristics. Multi-protocol label switching (MPLS) has proven strength in providing quality of service based data services due to its traffic engineering procedures. This paper presents a comprehensive experimental analysis of TCP variants under MPLS with emphasis on Tahoe, Reno and Vegas. Under different traffic load, it has been found that Reno and Tahoe fail to take advantage of MPLS features where as Vegas has shown promising results with almost stable constant end-to-end delay after a transient phase of delay fluctuations in the early stages of data transmission session. The stable end-to-end delay under MPLS makes Vegas an attractive choice for medium to large size real-time traffic.
The great deployment of IEEE 802.11 wireless networks has spawned momentous challenges for future data communication. Consumers often criticize the connectivity and performance related issues. Many of the routing prot...
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The great deployment of IEEE 802.11 wireless networks has spawned momentous challenges for future data communication. Consumers often criticize the connectivity and performance related issues. Many of the routing protocols are suggested for wireless LAN. Prominent steps for selection of routing protocols according to the nature of network environment produce better performance. We use DSDV routing protocols to evaluate the performance of TCP & UDP over wired cum wireless LAN. We use Network Simulator-2 with different parameters, generating different speeds of mobile nodes and different link capacity (bandwidth) with same packet size in every scenario. We compare TCP and UDP in terms of throughput, good put and other significant parameters to justify their performance in particular circumstances.
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