UML dynamic models are important for software analysis and design. Verifying UML dynamic models to find design errors earlier is a key issue for ensuring software quality. Because of the characteristics such as concur...
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UML dynamic models are important for software analysis and design. Verifying UML dynamic models to find design errors earlier is a key issue for ensuring software quality. Because of the characteristics such as concurrency and hierarchy, model checking of UML Statecharts and collaboration diagrams faces the problem of state explosion. In this paper, UML Statecharts is firstly structurally expressed by hierarchical automata and its semantics for open systems is introduced. Then, the synchronization composition of objects in UML collaboration diagrams is expatiated, based on which the global system behaviors can be constructed. Based on hierarchical automata and simulation relation between semantics structures, the compositional rules for verifying concurrent object systems are proposed. It makes possible that the construction of global state space will be unnecessary in model checking of UML collaboration diagrams. The hierarchical structures of UML Statecharts are also brought into the compositional verification, which makes the model checking of implementation models can be carried out through replacing detailed components by abstract specifications.
Given the multi-rate option in most 802.11 standards, rate adaptation based on dynamic channel condition is crucial to the system performance. This paper presents an efficient self-learning rate adaptation mechanism a...
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Given the multi-rate option in most 802.11 standards, rate adaptation based on dynamic channel condition is crucial to the system performance. This paper presents an efficient self-learning rate adaptation mechanism at MAC layer, called SLRA. SLRA takes both the temporal or spatial correlation and cha- nge into account. The rate selection has two steps: one is to evaluate the performance of current rate and decide whether to adjust the rate;the second is to calib- rate the decision according to the historical experiments of rate adjustment at similar channel status. We evaluate SLRA in 802.11 network and find that it can choose the right rate at most time and performs better than other sender-side adaptation schemes.
Emergent behavior is an essential feature in multi-agent systems and plays a significant role in the applications of agent technology. Because of the huge gap between individual agents' behaviors and those of the ...
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Emergent behavior is an essential feature in multi-agent systems and plays a significant role in the applications of agent technology. Because of the huge gap between individual agents' behaviors and those of the whole system, specifying and reasoning about emergent behaviors are notoriously difficult. Simulation has been the essential method to study emergent behaviors in multi-agent systems. In this paper, we report an experimental study of the emergent behaviors of self-organized agent communities, in which emergent behaviors play a crucial role. The experiments confirmed the results of a theoretical analysis of agent communities using a formal theory called scenario calculus. It further provided insight into the dynamic features of the system that were very difficult to obtain by using formal logic, such as the speed of convergence to the emergent states and the relationships between the convergence time and various parameters of self-organized agent communities systems.
Feature (gene) selection is a frequently used preprocessing technology for successful cancer classification task in microarray gene expression data analysis. Widely used gene selection approaches are mainly focused on...
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Feature (gene) selection is a frequently used preprocessing technology for successful cancer classification task in microarray gene expression data analysis. Widely used gene selection approaches are mainly focused on the filter methods. Filter methods are usually considered to be very effective and efficient for high-dimensional data. This paper reviews the existing filter methods, and shows the performance of the representative algorithms on microarray data by extensive experimental study. Surprisingly, the experimental results show that filter methods are not very effective on microarray data. We analyze the cause of the result and provide the basic ideas for potential solutions.
As an innovative distributed computing technique for sharing the memory resources in high-speed network, RAM Grid exploits the distributed free nodes, and provides remote memory for the nodes which are short of memory...
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As an innovative distributed computing technique for sharing the memory resources in high-speed network, RAM Grid exploits the distributed free nodes, and provides remote memory for the nodes which are short of memory. One of the RAM Grid systems named DRACO, tries to provide cooperative caching to improve the performance of the user node which has mass disk I/O but lacks local memory. However, the performance of DRACO is constrained with the network communication cost. In order to hide the latency of remote memory access and improve the caching performance, we proposed using push- based prefetching to enable the caching providers to push the potential useful memory pages to the user nodes. Specifically, for each caching provider, it employs sequential pattern mining techniques, which adapts to the characteristics of memory page access sequences, on locating useful memory pages for prefetching. We have verified the effectiveness of the proposed method through system analysis and trace-driven simulations.
Searching in large-scale unstructured peer-to-peer networks is challenging due to the lack of effective hint information to guide queries. In this paper, we propose POP, a parallel, collaborative and Probabilistic sea...
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Searching in large-scale unstructured peer-to-peer networks is challenging due to the lack of effective hint information to guide queries. In this paper, we propose POP, a parallel, collaborative and Probabilistic search mechanism, in which query messages are viewed as search units to collaborate with each other and aggregate the distributed hints during the search process. A scheme called distributed Bloom filter (DBF) is presented to propagate the hints with a bandwidth-aware manner, in which a node divides the received Bloom filter vector into subvectors and disseminates the fragments to its neighbors according to their bandwidth capacity. The effectiveness of POP is demonstrated through theoretical analysis and extensive simulations.
In wireless ad hoc networks, the flooding operation is an important utility function. To solve the broadcast storm problem, some efficient flooding schemes have been proposed. However, there also exist many problems i...
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In wireless ad hoc networks, the flooding operation is an important utility function. To solve the broadcast storm problem, some efficient flooding schemes have been proposed. However, there also exist many problems in these schemes, such as signal collision. In this paper, we propose an efficient flooding algorithm called EFDA based on the algorithm proposed in [1] (we reference the algorithm as EF1). Through theoretical analysis, our algorithm doesn't affect the local optimality gained by EF1. We have implemented our algorithm in ns-2 simulator, and the results show that exploiting directional antenna can reduce the number of signal collisions and our algorithm achieves better performance than pure flooding and EF1 due to smaller number of signal collisions.
There are many researches use peer-to-peer model to organize the Grid Information Service (GIS) and have been testified which be able to improve scalability and reliability of Grid environment. However, Data Grid Info...
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