44920541
Benefits of partial reconfigurability in circuit-switched WDM networks
We describe and study partially reconfigurable circuit-switched networks. These are dynamic networks in which partial, but not complete, flexibility of resource assignment is retained during the lifetime of a connection. In particular we analyse two examples of partially reconfigurable WDM networks with flexibility of wavelength assignment. In the first example, each connection in the network requires a main lightpath (whose wavelength must remain fixed) and a standby lightpath (whose wavelength may change). In the second example, the network contains two classes of connections with different service levels, one class reconfigurable and the other not. We propose two contrasting reconfiguration algorithms, and demonstrate that even a small amount of reconfigurability can yield significant performance gains, while a large amount of reconfigurability yields almost all the performance gain that would be attained by introducing complete wavelength conversion to the network.
26598527
Large Tandem Queueing Networks with Blocking
Systems consisting of many queues in series have been considered by Glynn and Whitt (1991) and Baccelli, Borovkov and Mairesse (2000). We extend their results to apply to situations where the queues have finite capacity and so various types of “blocking” can occur. The models correspond to max-plus type recursions, of simple form but in infinitely many dimensions; they are related to “percolation” problems of finding paths of maximum weight through a 2-dimensional lattice with random weights at the vertices. Topics treated include: laws of large numbers for the speed of customers progressing through the system; stationary behaviour for systems with external arrival processes; a functional central limit theorem describing the behaviour of the “front of the wave” progressing through a system which starts empty; stochastic orderings for waiting times of customers at successive queues. Several open problems are noted.
731954
Separating agreement from execution for byzantine fault tolerant services
We describe a new architecture for Byzantine fault tolerant state machine replication that separates agreement that orders requests from execution that processes requests. This separation yields two fundamental and practically significant advantages over previous architectures. First, it reduces replication costs because the new architecture can tolerate faults in up to half of the state machine replicas that execute requests. Previous systems can tolerate faults in at most a third of the combined agreement/state machine replicas. Second, separating agreement from execution allows a general privacy firewall architecture to protect confidentiality through replication. In contrast, replication in previous systems hurts confidentiality because exploiting the weakest replica can be sufficient to compromise the system. We have constructed a prototype and evaluated it running both microbenchmarks and an NFS server. Overall, we find that the architecture adds modest latencies to unreplicated systems and that its performance is competitive with existing Byzantine fault tolerant systems.
14705463
C to Java migration experiences
With the growing popularity of the Java programming language for both client and server side applications in network-centric computing, there is a rising need for programming libraries that can be easily integrated into Java programs. In a previous paper, we surveyed current strategies for integrating C source code into Java programs, pointed out their weaknesses and presented goals for an improved migration approach. In this paper, we present the Ephedra approach to software migration and report on the results of three case studies transliterating C source code to Java using the Ephedra environment.
12982947
Support Vector Learning for Semantic Argument Classification
The natural language processing community has recently experienced a growth of interest in domain independent shallow semantic parsing—the process of assigning a Who did What to Whom, When, Where, Why, How etc. structure to plain text. This process entails identifying groups of words in a sentence that represent these semantic arguments and assigning specific labels to them. It could play a key role in NLP tasks like Information Extraction, Question Answering and Summarization. We propose a machine learning algorithm for semantic role parsing, extending the work of Gildea and Jurafsky (2002), Surdeanu et al. (2003) and others. Our algorithm is based on Support Vector Machines which we show give large improvement in performance over earlier classifiers. We show performance improvements through a number of new features designed to improve generalization to unseen data, such as automatic clustering of verbs. We also report on various analytic studies examining which features are most important, comparing our classifier to other machine learning algorithms in the literature, and testing its generalization to new test set from different genre. On the task of assigning semantic labels to the PropBank (Kingsbury, Palmer, & Marcus, 2002) corpus, our final system has a precision of 84% and a recall of 75%, which are the best results currently reported for this task. Finally, we explore a completely different architecture which does not requires a deep syntactic parse. We reformulate the task as a combined chunking and classification problem, thus allowing our algorithm to be applied to new languages or genres of text for which statistical syntactic parsers may not be available.
8716869
Generating product-lines of product-families
GenVoca is a methodology and technology for generating product-lines, i.e. building variants of a program. The primitive components from which applications are constructed are refinements or layers, which are modules that implement a feature that many programs of a product-line can share. Unlike conventional components (e.g., COM, CORBA, EJB), a layer encapsulates fragments of multiple classes. Sets of fully formed classes can be produced by composing layers. Layers are modular, albeit unconventional, building blocks of programs. But what are the building blocks of layers? We argue that facets is an answer. A facet encapsulates fragments of multiple layers, and compositions of facets yields sets of fully formed layers. Facets arise when refinements scale from producing variants of individual programs to producing variants of multiple integrated programs, as typified byproduct families (e.g., MS Office). We present a mathematical model that explains relationships between layers and facets. We use the model to develop a generator for tools (i.e., product family) that are used in language-extensible Integrated Development Environments (IDEs).
4484500
Perception of Blended Emotions: From Video Corpus to Expressive Agent
Real life emotions are often blended and involve several simultaneous superposed or masked emotions. This paper reports on a study on the perception of multimodal emotional behaviors in Embodied Conversational Agents. This experimental study aims at evaluating if people detect properly the signs of emotions in different modalities (speech, facial expressions, gestures) when they appear to be superposed or masked. We compared the perception of emotional behaviors annotated in a corpus of TV interviews and replayed by an expressive agent at different levels of abstraction. The results provide insights on the use of such protocols for studying the effect of various models and modalities on the perception of complex emotions.