OpenRaiser/Intern-Atlas huggingface dataset:
Movie Recommendation Systems Using An Artificial Immune System
Venue: arXiv cs.NE 2008
Year: 2008

We apply the Artificial Immune System (AIS) technology to the Collaborative Filtering (CF) technology when we build the movie recommendation system. Two different affinity measure algorithms of AIS, Kendall tau and Weighted Kappa, are used to calculate the correlation coefficients for this movie recommendation system. From the testing we think that Weighted Kappa is more suitable than Kendall tau for movie problems.
Investigating Artificial Immune Systems For Job Shop Rescheduling In Changing Environments
Venue: arXiv cs.NE 2008
Year: 2008

Artificial immune system can be used to generate schedules in changing environments and it has been proven to be more robust than schedules developed using a genetic algorithm. Good schedules can be produced especially when the number of the antigens is increased. However, an increase in the range of the antigens had somehow affected the fitness of the immune system. In this research, we are trying to improve the result of the system by rescheduling the same problem using the same method while at the same time maintaining the robustness of the schedules.
A Locked Orthogonal Tree
Venue: arXiv cs.CG 2008
Year: 2008

We give a counterexample to a conjecture of Poon [Poo06] that any orthogonal tree in two dimensions can always be flattened by a continuous motion that preserves edge lengths and avoids self-intersection. We show our example is locked by extending results on strongly locked self-touching linkages due to Connelly, Demaine and Rote [CDR02] to allow zero-length edges as defined in [ADG07], which may be of independent interest. Our results also yield a locked tree with only eleven edges, which is the smallest known example of a locked tree.
It's Not What You Have, But How You Use It: Compromises in Mobile Device Use
Venue: arXiv cs.HC 2008
Year: 2008

As users begin to use many more devices for personal information management (PIM) than just the traditional desktop computer, it is essential for HCI researchers to understand how these devices are being used in the wild and their roles in users' information environments. We conducted a study of 220 knowledge workers about their devices, the activities they performed on each, and the groups of devices used together. Our findings indicate that several devices are often used in groups; integrated multi-function portable devices have begun to replace single-function devices for communication (e.g. email and IM). Users use certain features opportunistically because they happen to be carrying a multi-function device with them. The use of multiple devices and multi-function devices is fraught with compromises as users must choose and make trade-offs among various factors.
Is SP BP?
Venue: arXiv cs.IT 2008
Year: 2008

The Survey Propagation (SP) algorithm for solving $k$-SAT problems has been shown recently as an instance of the Belief Propagation (BP) algorithm. In this paper, we show that for general constraint-satisfaction problems, SP may not be reducible from BP. We also establish the conditions under which such a reduction is possible. Along our development, we present a unification of the existing SP algorithms in terms of a probabilistically interpretable iterative procedure -- weighted Probabilistic Token Passing.
Methods to integrate a language model with semantic information for a word prediction component
Venue: arXiv cs.CL 2008
Year: 2008

Most current word prediction systems make use of n-gram language models (LM) to estimate the probability of the following word in a phrase. In the past years there have been many attempts to enrich such language models with further syntactic or semantic information. We want to explore the predictive powers of Latent Semantic Analysis (LSA), a method that has been shown to provide reliable information on long-distance semantic dependencies between words in a context. We present and evaluate here several methods that integrate LSA-based information with a standard language model: a semantic cache, partial reranking, and different forms of interpolation. We found that all methods show significant improvements, compared to the 4-gram baseline, and most of them to a simple cache model as well.
On the Complexity of Binary Samples
Venue: arXiv cs.DM 2008
Year: 2008

Consider a class $\mH$ of binary functions $h: X\to\{-1, +1\}$ on a finite interval $X=[0, B]\subset \Real$. Define the {\em sample width} of $h$ on a finite subset (a sample) $S\subset X$ as $\w_S(h) \equiv \min_{x\in S} |\w_h(x)|$, where $\w_h(x) = h(x) \max\{a\geq 0: h(z)=h(x), x-a\leq z\leq x+a\}$. Let $\mathbb{S}_\ell$ be the space of all samples in $X$ of cardinality $\ell$ and consider sets of wide samples, i.e., {\em hypersets} which are defined as $A_{β, h} = \{S\in \mathbb{S}_\ell: \w_{S}(h) \geq β\}$. Through an application of the Sauer-Shelah result on the density of sets an upper estimate is obtained on the growth function (or trace) of the class $\{A_{β, h}: h\in\mH\}$, $β>0$, i.e., on the number of possible dichotomies obtained by intersecting all hypersets with a fixed collection of samples $S\in\mathbb{S}_\ell$ of cardinality $m$. The estimate is $2\sum_{i=0}^{2\lfloor B/(2β)\rfloor}{m-\ell\choose i}$.
Partitioning the Threads of a Mobile System
Venue: arXiv cs.OH 2008
Year: 2008

In this paper, we show how thread partitioning helps in proving properties of mobile systems. Thread partitioning consists in gathering the threads of a mobile system into several classes. The partitioning criterion is left as a parameter of both the mobility model and the properties we are interested in. Then, we design a polynomial time abstract interpretation-based static analysis that counts the number of threads inside each partition class.
A proposal to a generalised splicing with a self assembly approach
Venue: arXiv cs.DM 2008
Year: 2008

Theory of splicing is an abstract model of the recombinant behaviour of DNAs. In a splicing system, two strings to be spliced are taken from the same set and the splicing rule is from another set. Here we propose a generalised splicing (GS) model with three components, two strings from two languages and a splicing rule from third component. We propose a generalised self assembly (GSA) of strings. Two strings $u_1xv_1$ and $u_2xv_2$ self assemble over $x$ and generate $u_1xv_2$ and $u_2xv_1$. We study the relationship between GS and GSA. We study some classes of generalised splicing languages with the help of generalised self assembly.
Capacity of Wireless Networks within o(log(SNR)) - the Impact of Relays, Feedback, Cooperation and Full-Duplex Operation
Venue: arXiv cs.IT 2008
Year: 2008

Recent work has characterized the sum capacity of time-varying/frequency-selective wireless interference networks and $X$ networks within $o(\log({SNR}))$, i.e., with an accuracy approaching 100% at high SNR (signal to noise power ratio). In this paper, we seek similar capacity characterizations for wireless networks with relays, feedback, full duplex operation, and transmitter/receiver cooperation through noisy channels. First, we consider a network with $S$ source nodes, $R$ relay nodes and $D$ destination nodes with random time-varying/frequency-selective channel coefficients and global channel knowledge at all nodes. We allow full-duplex operation at all nodes, as well as causal noise-free feedback of all received signals to all source and relay nodes. The sum capacity of this network is characterized as $\frac{SD}{S+D-1}\log({SNR})+o(\log({SNR}))$. The implication of the result is that the capacity benefits of relays, causal feedback, transmitter/receiver cooperation through physical channels and full duplex operation become a negligible fraction of the network capacity at high SNR. Some exceptions to this result are also pointed out in the paper. Second, we consider a network with $K$ full duplex nodes with an independent message from every node to every other node in the network. We find that the sum capacity of this network is bounded below by $\frac{K(K-1)}{2K-2}+o(\log({SNR}))$ and bounded above by $\frac{K(K-1)}{2K-3}+o(\log({SNR}))$.
Message-Passing Decoding of Lattices Using Gaussian Mixtures
Venue: arXiv cs.IT 2008
Year: 2008

A lattice decoder which represents messages explicitly as a mixture of Gaussians functions is given. In order to prevent the number of functions in a mixture from growing as the decoder iterations progress, a method for replacing N Gaussian functions with M Gaussian functions, with M < N, is given. A squared distance metric is used to select functions for combining. A pair of selected Gaussians is replaced by a single Gaussian with the same first and second moments. The metric can be computed efficiently, and at the same time, the proposed algorithm empirically gives good results, for example, a dimension 100 lattice has a loss of 0.2 dB in signal-to-noise ratio at a probability of symbol error of 10^{-5}.
Modelling and Analysis of the Distributed Coordination Function of IEEE 802.11 with Multirate Capability
Venue: arXiv cs.NI 2008
Year: 2008

The aim of this paper is twofold. On one hand, it presents a multi-dimensional Markovian state transition model characterizing the behavior at the Medium Access Control (MAC) layer by including transmission states that account for packet transmission failures due to errors caused by propagation through the channel, along with a state characterizing the system when there are no packets to be transmitted in the queue of a station (to model non-saturated traffic conditions). On the other hand, it provides a throughput analysis of the IEEE 802.11 protocol at the data link layer in both saturated and non-saturated traffic conditions taking into account the impact of both transmission channel and multirate transmission in Rayleigh fading environment. Simulation results closely match the theoretical derivations confirming the effectiveness of the proposed model.
On Approximating Frequency Moments of Data Streams with Skewed Projections
Venue: arXiv cs.DS 2008
Year: 2008

We propose skewed stable random projections for approximating the pth frequency moments of dynamic data streams (0<p<=2), which has been frequently studied in theoretical computer science and database communities. Our method significantly (or even infinitely when p->1) improves previous methods based on (symmetric) stable random projections. Our proposed method is applicable to data streams that are (a) insertion only (the cash-register model); or (b) always non-negative (the strict Turnstile model), or (c) eventually non-negative at check points. This is only a minor restriction for practical applications. Our method works particularly well when p = 1+/- Δand Δis small, which is a practically important scenario. For example, Δmay be the decay rate or interest rate, which are usually small. Of course, when Δ= 0, one can compute the 1th frequent moment (i.e., the sum) essentially error-free using a simple couter. Our method may be viewed as a ``genearlized counter'' in that it can count the total value in the future, taking in account of the effect of decaying or interest accruement. In a summary, our contributions are two-fold. (A) This is the first propsal of skewed stable random projections. (B) Based on first principle, we develop various statistical estimators for skewed stable distributions, including their variances and error (tail) probability bounds, and consequently the sample complexity bounds.
New Estimation Procedures for PLS Path Modelling
Venue: arXiv cs.LG 2008
Year: 2008

Given R groups of numerical variables X1, ... XR, we assume that each group is the result of one underlying latent variable, and that all latent variables are bound together through a linear equation system. Moreover, we assume that some explanatory latent variables may interact pairwise in one or more equations. We basically consider PLS Path Modelling's algorithm to estimate both latent variables and the model's coefficients. New "external" estimation schemes are proposed that draw latent variables towards strong group structures in a more flexible way. New "internal" estimation schemes are proposed to enable PLSPM to make good use of variable group complementarity and to deal with interactions. Application examples are given.
Small Is Not Always Beautiful
Venue: arXiv cs.NI 2008
Year: 2008

Peer-to-peer content distribution systems have been enjoying great popularity, and are now gaining momentum as a means of disseminating video streams over the Internet. In many of these protocols, including the popular BitTorrent, content is split into mostly fixed-size pieces, allowing a client to download data from many peers simultaneously. This makes piece size potentially critical for performance. However, previous research efforts have largely overlooked this parameter, opting to focus on others instead. This paper presents the results of real experiments with varying piece sizes on a controlled BitTorrent testbed. We demonstrate that this parameter is indeed critical, as it determines the degree of parallelism in the system, and we investigate optimal piece sizes for distributing small and large content. We also pinpoint a related design trade-off, and explain how BitTorrent's choice of dividing pieces into subpieces attempts to address it.
Complexity of Decoding Positive-Rate Reed-Solomon Codes
Venue: arXiv cs.IT 2008
Year: 2008

The complexity of maximal likelihood decoding of the Reed-Solomon codes $[q-1, k]_q$ is a well known open problem. The only known result in this direction states that it is at least as hard as the discrete logarithm in some cases where the information rate unfortunately goes to zero. In this paper, we remove the rate restriction and prove that the same complexity result holds for any positive information rate. In particular, this resolves an open problem left in [4], and rules out the possibility of a polynomial time algorithm for maximal likelihood decoding problem of Reed-Solomon codes of any rate under a well known cryptographical hardness assumption. As a side result, we give an explicit construction of Hamming balls of radius bounded away from the minimum distance, which contain exponentially many codewords for Reed-Solomon code of any positive rate less than one. The previous constructions only apply to Reed-Solomon codes of diminishing rates. We also give an explicit construction of Hamming balls of relative radius less than 1 which contain subexponentially many codewords for Reed-Solomon code of rate approaching one.
Bayesian Nonlinear Principal Component Analysis Using Random Fields
Venue: arXiv cs.CV 2008
Year: 2008

We propose a novel model for nonlinear dimension reduction motivated by the probabilistic formulation of principal component analysis. Nonlinearity is achieved by specifying different transformation matrices at different locations of the latent space and smoothing the transformation using a Markov random field type prior. The computation is made feasible by the recent advances in sampling from von Mises-Fisher distributions.
New Bounds for the Capacity Region of the Finite-State Multiple Access Channel
Venue: arXiv cs.IT 2008
Year: 2008

The capacity region of the Finite-State Multiple Access Channel (FS-MAC) with feedback that may be an arbitrary time-invariant function of the channel output samples is considered. We provided a sequence of inner and outer bounds for this region. These bounds are shown to coincide, and hence yield the capacity region, of FS-MACs where the state process is stationary and ergodic and not affected by the inputs, and for indecomposable FS-MAC when feedback is not allowed. Though the capacity region is `multi-letter' in general, our results yield explicit conclusions when applied to specific scenarios of interest.
Approximating General Metric Distances Between a Pattern and a Text
Venue: arXiv cs.DS 2008
Year: 2008

Let $T=t_0 ... t_{n-1}$ be a text and $P = p_0 ... p_{m-1}$ a pattern taken from some finite alphabet set $Σ$, and let $\dist$ be a metric on $Σ$. We consider the problem of calculating the sum of distances between the symbols of $P$ and the symbols of substrings of $T$ of length $m$ for all possible offsets. We present an $ε$-approximation algorithm for this problem which runs in time $O(\frac{1}{ε^2}n\cdot \mathrm{polylog}(n,\absΣ))$
Discrete Complex Structure on Surfel Surfaces
Venue: arXiv cs.CG 2008
Year: 2008

This paper defines a theory of conformal parametrization of digital surfaces made of surfels equipped with a normal vector. The main idea is to locally project each surfel to the tangent plane, therefore deforming its aspect-ratio. It is a generalization of the theory known for polyhedral surfaces. The main difference is that the conformal ratios that appear are no longer real in general. It yields a generalization of the standard Laplacian on weighted graphs.
Zero-knowledge authentication schemes from actions on graphs, groups, or rings
Venue: arXiv cs.CR 2008
Year: 2008

We propose a general way of constructing zero-knowledge authentication schemes from actions of a semigroup on a set, without exploiting any specific algebraic properties of the set acted upon. Then we give several concrete realizations of this general idea, and in particular, we describe several zero-knowledge authentication schemes where forgery (a.k.a. impersonation) is NP-hard. Computationally hard problems that can be employed in these realizations include (Sub)graph Isomorphism, Graph Colorability, Diophantine Problem, and many others.
Longest paths in Planar DAGs in Unambiguous Logspace
Venue: arXiv cs.CC 2008
Year: 2008

We show via two different algorithms that finding the length of the longest path in planar directed acyclic graph (DAG) is in unambiguous logspace UL, and also in the complement class co-UL. The result extends to toroidal DAGs as well.
A review of the Statistical Mechanics approach to Random Optimization Problems
Venue: arXiv cs.CC 2008
Year: 2008

We review the connection between statistical mechanics and the analysis of random optimization problems, with particular emphasis on the random k-SAT problem. We discuss and characterize the different phase transitions that are met in these problems, starting from basic concepts. We also discuss how statistical mechanics methods can be used to investigate the behavior of local search and decimation based algorithms.
A Radar-Shaped Statistic for Testing and Visualizing Uniformity Properties in Computer Experiments
Venue: arXiv cs.LG 2008
Year: 2008

In the study of computer codes, filling space as uniformly as possible is important to describe the complexity of the investigated phenomenon. However, this property is not conserved by reducing the dimension. Some numeric experiment designs are conceived in this sense as Latin hypercubes or orthogonal arrays, but they consider only the projections onto the axes or the coordinate planes. In this article we introduce a statistic which allows studying the good distribution of points according to all 1-dimensional projections. By angularly scanning the domain, we obtain a radar type representation, allowing the uniformity defects of a design to be identified with respect to its projections onto straight lines. The advantages of this new tool are demonstrated on usual examples of space-filling designs (SFD) and a global statistic independent of the angle of rotation is studied.
Using Alloy to model-check visual design notations
Venue: arXiv cs.SE 2008
Year: 2008

This paper explores the process of validation for the abstract syntax of a graphical notation. We define an unified specification for five of the UML diagrams used by the Discovery Method and, in this document, we illustrate how diagrams can be represented in Alloy and checked against our specification in order to know if these are valid under the Discovery notation.
Software graphs and programmer awareness
Venue: arXiv cs.SE 2008
Year: 2008

Dependencies between types in object-oriented software can be viewed as directed graphs, with types as nodes and dependencies as edges. The in-degree and out-degree distributions of such graphs have quite different forms, with the former resembling a power-law distribution and the latter an exponential distribution. This effect appears to be independent of application or type relationship. A simple generative model is proposed to explore the proposition that the difference arises because the programmer is aware of the out-degree of a type but not of its in-degree. The model reproduces the two distributions, and compares reasonably well to those observed in 14 different type relationships across 12 different Java applications.
Authentication over Noisy Channels
Venue: arXiv cs.IT 2008
Year: 2008

In this work, message authentication over noisy channels is studied. The model developed in this paper is the authentication theory counterpart of Wyner's wiretap channel model. Two types of opponent attacks, namely impersonation attacks and substitution attacks, are investigated for both single message and multiple message authentication scenarios. For each scenario, information theoretic lower and upper bounds on the opponent's success probability are derived. Remarkably, in both scenarios, lower and upper bounds are shown to match, and hence the fundamental limit of message authentication over noisy channels is fully characterized. The opponent's success probability is further shown to be smaller than that derived in the classic authentication model in which the channel is assumed to be noiseless. These results rely on a proposed novel authentication scheme in which key information is used to provide simultaneous protection again both types of attacks.
Stackelberg Network Pricing Games
Venue: arXiv cs.DS 2008
Year: 2008

We study a multi-player one-round game termed Stackelberg Network Pricing Game, in which a leader can set prices for a subset of $m$ priceable edges in a graph. The other edges have a fixed cost. Based on the leader's decision one or more followers optimize a polynomial-time solvable combinatorial minimization problem and choose a minimum cost solution satisfying their requirements based on the fixed costs and the leader's prices. The leader receives as revenue the total amount of prices paid by the followers for priceable edges in their solutions, and the problem is to find revenue maximizing prices. Our model extends several known pricing problems, including single-minded and unit-demand pricing, as well as Stackelberg pricing for certain follower problems like shortest path or minimum spanning tree. Our first main result is a tight analysis of a single-price algorithm for the single follower game, which provides a $(1+ε) \log m$-approximation for any $ε>0$. This can be extended to provide a $(1+ε)(\log k + \log m)$-approximation for the general problem and $k$ followers. The latter result is essentially best possible, as the problem is shown to be hard to approximate within $\mathcal{O(\log^εk + \log^εm)$. If followers have demands, the single-price algorithm provides a $(1+ε)m^2$-approximation, and the problem is hard to approximate within $\mathcal{O(m^ε)$ for some $ε>0$. Our second main result is a polynomial time algorithm for revenue maximization in the special case of Stackelberg bipartite vertex cover, which is based on non-trivial max-flow and LP-duality techniques. Our results can be extended to provide constant-factor approximations for any constant number of followers.