ppxscal/embedding_network huggingface dataset:
Engineering authority and trust in cyberspace: the OM-AM and RBAC way
Authors: Ravi Sandhu
Venue: Proceedings of the fifth ACM workshop on Role-based access control (2000)

Information systems of the future will be large-scale, highly decentralized, pervasive, span organizational boundaries and evolve rapidly. Effective security in this cyberspace will require engineering authority and trust retationships across organizations and individuals. In this paper we propose the four-layer OM-AM framework for this purpose. OM-AM comprises objective, model, architecture and mechanism layers in this sequence. The objective and model (OM) layers articulate whatthe security objective and tradeoffs are, while the architecture and mechanism (AM) layers address howto meet these requirements. The hyphen in OM-AM emphasizes the shift from what to how. These layers are roughly analogous to a network protocol stack with a many-to-many relationship between successive layers, and most certainly do not imply a top-down waterfall-style software engineering process. OM-AM is an excellent match to the policy-neutral and flexible nature of role-based access control (RBAC). This paper describes and motivates the OM-AM framework and presents a case study in applying it in a distributed RBAC application.
Stable and fault-tolerant object allocation
Authors: Gregory Johnson, Ambuj K. Singh
Venue: Proceedings of the nineteenth annual ACM symposium on Principles of distributed computing (2000)

Support for efficient dynamic migration and replication of objects is essential for achieving adequate performance and scalability. Traditional solutions to the problem focused on competitiveness. This means that the algorithm's complexity matches the offline adversary's complexity within an acceptable ratio. We define and study the allocation problem under two new measures: stability and fault tolerance. Stability considers the performance of an object allocation algorithm when the object access patterns at the individual nodes of a distributed system stabilize. We present a new algorithm for uniform networks based on the idea of sliding windows. Besides being optimally competitive, the algorithm also exhibits good stability. For fault-tolerance, we consider the performance of allocation algorithms when at least t copies need to be maintained. We derive a lower bound on the competitiveness of such algorithms. Finally, we modify our earlier solution so that it is also optimally fault-tolerant.
Speculation techniques for improving load related instruction scheduling
Authors: Adi Yoaz, Mattan Erez, Ronny Ronen, Stephan Jourdan
Venue: Proceedings of the 26th annual international symposium on Computer architecture (1999)

State of the art microprocessors achieve high performance by executing multiple instructions per cycle. In an out-of-order engine, the instruction scheduler is responsible for dispatching instructions to execution units based on dependencies, latencies, and resource availability. Most existing instruction schedulers are doing a less than optimal job of scheduling memory accesses and instructions dependent on them, for the following reasons: bull; Memory dependencies cannot be resolved prior to execution, so loads are not advanced ahead of preceding stores. bull; The dynamic latencies of load instructions are unknown, so scheduling dependent instructions is based on either optimistic load-use delay (may cause re-scheduling and re-execution) or pessimistic delay (creating unnecessary delays). bull; Memory pipelines are more expensive than other execution units, and as such, are a scarce resource. Currently, an increase in the memory execution bandwidth is usually achieved through multi-banked caches where bank conflicts limit efficiency.In this paper we present three techniques to address these scheduler limitations. One is to improve the scheduling of load instructions by using a simple memory disambiguation mechanism. The second is to improve the scheduling of load dependent instructions by employing a Data Cache Hit-Miss Predictor to predict the dynamic load latencies. And the third is to improve the efficiency of load scheduling in a multi-banked cache through Cache-Bank Prediction.
Numerical Computation of Rank-One Convex Envelopes
Authors: Georg Dolzmann
Venue: SIAM Journal on Numerical Analysis (1999)

We describe an algorithm for the numerical computation of the rank-one convex envelope of a function $f:\MM^{m\times n}\rightarrow\RR$. We prove its convergence and an error estimate in $L^\infty$.
A comparison of tools for building GOMS models
Authors: Lynn K. Baumeister, Bonnie E. John, Michael D. Byrne
Venue: Proceedings of the SIGCHI conference on Human factors in computing systems (2000)

We compare three tools for creating GOMS models, QGOMS [2), CATHCI (17) and GLEAN3 [12], along several dimensions. We examine the representation and available constructs in each tool, the qualitative and quantitative design information provided, the support for building cognitively plausible models, and pragmatics about using each tool (e.g., how easy it is to modify a model). While each tool has its strengths, they all leave something to be desired as a practical UI design tool.
An optimisation scheme for coalesce/valid time selection operator sequences
Authors: Costas Vassilakis
Venue: ACM SIGMOD Record (2000)

Queries in temporal databases often employ the coalesce operator, either to coalesce results of projections, or data which are not coalesced upon storage. Therefore, the performance and the optimisation schemes utilised for this operator is of major importance for the performance of temporal DBMSs. Insofar, performance studies for various algorithms that implement this operator have been conducted, however, the joint optimisation of the coalesce operator with other algebraic operators that appear in the query execution plan has only received minimal attention. In this paper, we propose a scheme for combining the coalesce operator with selection operators which are applied to the valid time of the tuples produced from a coalescing operation. The proposed scheme aims at reducing the number of tuples that a coalescing operator must process, while at the same time allows the optimiser to exploit temporal indices on the valid time of the data.
Efficient variants of Huffman codes in high level languages
Authors: Y. Choueka, S. T. Klein, Y. Perl
Venue: Proceedings of the 8th annual international ACM SIGIR conference on Research and development in information retrieval (1985)

Although it is well-known that Huffman Codes are optimal for text compression in a character-per-character encoding scheme, they are seldom used in practical situations since they require a bit-per-bit decoding algorithm, which has to be written in some assembly language, and will perform rather slowly. A number of methods are presented that avoid these difficulties. The decoding algorithms efficiently process the encoded string on a byte-per-byte basis, are faster than the original algorithm, and can be programmed in any high level language. This is achieved at the cost of storing some tables in the internal memory, but with no loss in the compression savings of the optimal Huffman codes. The internal memory space needed can be reduced either at the cost of increased processing time, or by using non-binary Huffman codes, which give sub-optimal compression. Experimental results for English and Hebrew text are also presented.
Online index rebuild
Authors: Nagavamsi Ponnekanti, Hanuma Kodavalla
Venue: ACM SIGMOD Record (2000)

In this paper we present an efficient method to do online rebuild of a B+-tree index. This method has been implemented in Sybase Adaptive Server Enterprise (ASE) Version 12.0. It provides high concurrency, does minimal amount of logging, has good performance and does not deadlock with other index operations. It copies the index rows to newly allocated pages in the key order so that good space utilization and clustering are achieved. The old pages are deallocated during the process. Our algorithm differs from the previously published online index rebuild algorithms in two ways. It rebuilds multiple leaf pages and then propagates the changes to higher levels. Also, while propagating the leaf level changes to higher levels, level 11 pages are reorganized, eliminating the need for a separate pass. Our performance study shows that our approach results in significant reduction in logging and CPU time. Also, our approach uses the same concurrency control mechanism as split and shrink operations, which made it attractive for implementation.
Improving cache performance in dynamic applications through data and computation reorganization at run time
Authors: Chen Ding, Ken Kennedy
Venue: ACM SIGPLAN Notices (1999)

With the rapid improvement of processor speed, performance of the memory hierarchy has become the principal bottleneck for most applications. A number of compiler transformations have been developed to improve data reuse in cache and registers, thus reducing the total number of direct memory accesses in a program. Until now, however, most data reuse transformations have been static---applied only at compile time. As a result, these transformations cannot be used to optimize irregular and dynamic applications, in which the data layout and data access patterns remain unknown until run time and may even change during the computation.In this paper, we explore ways to achieve better data reuse in irregular and dynamic applications by building on the inspector-executor method used by Saltz for run-time parallelization. In particular, we present and evaluate a dynamic approach for improving both computation and data locality in irregular programs. Our results demonstrate that run-time program transformations can substantially improve computation and data locality and, despite the complexity and cost involved, a compiler can automate such transformations, eliminating much of the associated run-time overhead.
Nonsystematic perfect codes
Authors: Kevin T. Phelps, Mike LeVan
Venue: SIAM Journal on Discrete Mathematics (1999)

We investigate nonsystematic perfect binary codes of length n, establishing that nonsystematic perfect codes of length n exist for all admissible $n \geq 15$. This improves on the result of Avgustinovich and Solov'eva [ Proc. 5th Internat. Workshop Algebraic and Combinatorial Coding Theory, Cosopol, Bulgaria, 1996, pp. 15--19] who have established the existence of such codes for $n\geq 255$. We also provide the results of a computer investigation of nonsystematic perfect codes of length 15.
Robust Stability of Multivariate Polynomials, Part 2: PolytopicCoefficient Variations
Authors: V. L. Kharitonov J. A. Torres-Munoz M. I. Ramirez-Sosa
Venue: Multidimensional Systems and Signal Processing (1999)

This paper deals with robustness of stability propety of a class of multivariate polynomials, recently introduced in kharjt. The aim is to show the use of this class when analyzing stability of mutivariate polynomial families with polytopic coefficient variations. This study is developed on the basis of some known stability results for polytopic families of scattering Hurwitz stable (SHS) as well as strict sense stable (SSS) multivariate polynomials.
A semantics for imprecise exceptions
Authors: Simon Peyton Jones, Alastair Reid, Fergus Henderson, Tony Hoare, Simon Marlow
Venue: Proceedings of the ACM SIGPLAN 1999 conference on Programming language design and implementation (1999)

Some modern superscalar microprocessors provide only imprecise exceptions. That is, they do not guarantee to report the same exception that would be encountered by a straightforward sequential execution of the program. In exchange, they offer increased performance or decreased chip area (which amount to much the same thing).This performance/precision tradeoff has not so far been much explored at the programming language level. In this paper we propose a design for imprecise exceptions in the lazy functional programming language Haskell. We discuss several designs, and conclude that imprecision is essential if the language is still to enjoy its current rich algebra of transformations. We sketch a precise semantics for the language extended with exceptions.The paper shows how to extend Haskell with exceptions without crippling the language or its compilers. We do not yet have enough experience of using the new mechanism to know whether it strikes an appropriate balance between expressiveness and performance.
Multi-Scale Image Analysis by Pyramidal Algorithms
Authors: Jules-Raymond Tapamo
Venue: Journal of Mathematical Imaging and Vision (1999)

Quadtree representation presents many advantages in image analysis because of its better manipulation at different scales. In computer vision one frequently faces the problem of multi-scale analysis. We use a syntactic representation of quadtree to analyse images in the Haar base with pyramidal algorithms in linear time. We present applications in dynamic filtering, in compression and image segmentation.
Test Data Decompression for Multiple Scan Designs with Boundary Scan
Authors: Janusz Rajski, Jerzy Tyszer, Nadime Zacharia
Venue: IEEE Transactions on Computers (1998)

The paper presents an efficient scheme to compress and decompress in parallel deterministic test patterns for circuits with multiple scan chains. It employs a boundary-scan-based environment for high quality testing with flexible trade-offs between test data volume and test application time while achieving a complete fault coverage for any fault model for which test cubes are obtainable. It also reduces bandwidth requirements, as all test cube transfers involve compressed data. The test patterns are generated by the reseeding of a two-dimensional hardware structure which is comprised of a linear feedback shift register (LFSR), a network of exclusive-or (XOR) gates used to scramble the bits of test vectors, and extra feedbacks which allow including internal scan flip-flops into the decompressor structure to minimize the area overhead. The test data decompressor operates in two modes: pseudorandom and deterministic. In the first mode, the pseudorandom pattern generator (PRPG) is used purely as a generator of test vectors. In the latter case, variable-length seeds are serially scanned through the boundary-scan interface into the PRPG and parts of internal scan chains and, subsequently, a decompression is performed in parallel by means of the PRPG and selected scan flip-flops interconnected to form the decompression device. Extensive experiments with the largest ISCAS' 89 benchmarks show that the proposed technique greatly reduces the amount of test data in a cost effective manner.
Performance of coherent MQAM schemes in the presence of frequence-selective Rayleigh fading and CCI4
Authors: Zengjun Xiang, Tho Le-Ngoc, Guangguo Bi
Venue: Mobile Networks and Applications (2000)

Performance of a coherent MQAM system in the presence of frequency-selective Rayleigh fading, co-channel interference (CCI) and additive white Gaussian noise (AWGN) is presented. Square-root raised-cosine filters are used in both the transmitter and receiver for an optimum performance in a band-limited AWGN channel. Frequency-selective Rayleigh fading channel is modeled as a two-ray model. Based on the characteristic functions of the received signals and a discrete Fourier transform (DFT) method, an analytical procedure to compute the error probability is derived. Numerical results for an illustrative example of a 16QAM system are given. Effects of CCI and frequency-selective fading on the system performance are examined. Accuracy of the proposed method is discussed in comparison with other simulation and analytical techniques.
A Collocation Method for the Generalized Airfoil Equation for an Airfoil with a Flap
Authors: L. Scuderi
Venue: SIAM Journal on Numerical Analysis (1998)

We are concerned with the numerical solution of the generalized airfoil equation for an airfoil with a flap by means of global algebraic polynomial approximants. This problem has been considered in a recent paper by Monegato and Sloan [SIAM J. Numer. Anal., 34 (1997), pp. 2288--2305], where the authors proved the stability and convergence of a Galerkin method based on high order polynomials. They also presented very promising numerical results for the corresponding collocation method but left the theoretical results of stability and convergence as an open problem. We have succeeded in proving the stability and convergence properties of this collocation method by slightly modifying it in the neighborhood of the flap. The rate of convergence we have derived for our collocation method is very similar to that of the above Galerkin method.
A formal approach for designing CORBA based applications
Authors: Matteo Pradella, Matteo Rossi, Dino Mandrioli, Alberto Coen-Porisini
Venue: Proceedings of the 22nd international conference on Software engineering (2000)

The design of distributed applications in a CORBA based environment can be carried out by means of an incremental approach, which starts from the specification and leads to the high level architectural design. This is done by introducing in the specification all typical elements of CORBA and by providing a methodological support to the designers. The paper discusses a methodology to transform a formal specification written in TRIO into a high level design document written using an extension of TRIO named TC. The TC language is suited to formally describe the high level architecture of a CORBA based application. The methodology and the associated language are presented by means of an example involving a real Supervision and Control System.
Typechecking for XML transformers
Authors: Tova Milo, Dan Suciu, Victor Vianu
Venue: Proceedings of the nineteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems (2000)

We study the typechecking problem for XML transformers: given an XML transformation program and a DTD for the input XML documents, check whether every result of the program conforms to a specified output DTD. We model XML transformers using a novel device called a k-pebble transducer, that can express most queries without data-value joins in XML-QL, XSLT, and other XML query languages. Types are modeled by regular tree languages, a nobust extension of DTDs. The main result of the paper is that typechecking for k-pebble transducers is decidable. Consequently, typechecking can be performed for a broad range of XML transformation languages, including XML-QL and a fragment of XSLT.
ISDN: The New, All-digital Network
Authors: Allen Hauf
Venue: International Journal of Network Management (1996)

The burgeoning acceptance of ISDN in the United States is leading to increased availability of ISDN equipment worldwide. This worldwide availability of equipment, in turn, will lead to increased competition and more selection as network managers deploy multinational ISDN solutions.
Architectural support for the cache based vector computation
Authors: C. K. Yuen
Venue: ACM SIGARCH Computer Architecture News (1999)

The possibility of providing vector computation support to microprocessors is studied. It is suggested that frame registers pointing to vector elements stored in the cache can be used to stream data to and from vector arithmetic pipelines.
What is a recursive module?
Authors: Karl Crary, Robert Harper, Sidd Puri
Venue: ACM SIGPLAN Notices (1999)

A hierarchical module system is an effective tool for structuring large programs. Strictly hierarchical module systems impose an acyclic ordering on import dependencies among program units. This can impede modular programming by forcing mutually-dependent components to be consolidated into a single module. Recently there have been several proposals for module systems that admit cyclic dependencies, but it is not clear how these proposals relate to one another, nor how one might integrate them into an expressive module system such as that of ML.To address this question we provide a type-theoretic analysis of the notion of a recursive module in the context of a "phase-distinction" formalism for higher-order module systems. We extend this calculus with a recursive module mechanism and a new form of signature, called a recursively dependent signature, to support the definition of recursive modules. These extensions are justified by an interpretation in terms of more primitive language constructs. This interpretation may also serve as a guide for implementation.
Helper agent: designing an assistant for human-human interaction in a virtual meeting space
Authors: Katherine Isbister, Hideyuki Nakanishi, Toru Ishida, Cliff Nass
Venue: Proceedings of the SIGCHI conference on Human factors in computing systems (2000)

This paper introduces a new application area for agents in the computer interface: the support of human-human interaction. We discuss an interface agent prototype that is designed to support human-human communication in virtual environments. The prototype interacts with users strategically during conversation, spending most of its time listening. The prototype mimics a party host, trying to find a safe common topic for guests whose conversation has lagged. We performed an experimental evaluation of the prototype's ability to assist in cross-cultural conversations. We designed the prototype to introduce safe or unsafe topics to conversation pairs, through a series of questions and suggestions. The agent made positive contributions to participants' experience of the conversation, influenced their perception of each other and of each others' national group, and even seemed to effect their style of behavior. We discuss the implications of our research for the design of social agents to support human-human interaction.
On-Line 3-Chromatic Graphs I. Triangle-Free Graphs
Authors: András Gyárfás, Zoltán Király, Jeno Lehel
Venue: SIAM Journal on Discrete Mathematics (1999)

This is the first half of a two-part paper devoted to on-line 3-colorable graphs. Here on-line 3-colorable triangle-free graphs are characterized by a finite list of forbidden induced subgraphs. The key role in our approach is played by the family of graphs which are both triangle- and (2K2 + K1)-free. Characterization of this family is given by introducing a bipartite modular decomposition concept. This decomposition, combined with the greedy algorithm, culminates in an on-line 3-coloring algorithm for this family. On the other hand, based on the characterization of this family, all 22 forbidden subgraphs of on-line 3-colorable triangle-free graphs are determined. As a corollary, we obtain the 10 forbidden subgraphs of on-line 3-colorable bipartite graphs. The forbidden subgraphs in the finite basis characterization are on-line 4-critical, i.e., they are on-line 4-chromatic but their proper induced subgraphs are on-line 3-colorable. The results of this paper are applied in the companion paper [Discrete Math., 177 (1997), pp. 99--122] to obtain the finite basis characterization of connected on-line 3-colorable graphs (with 51 4-critical subgraphs). However, perhaps surprisingly, connectivity (or the triangle-free property) is essential in a finite basis characterization: there are infinitely many on-line 4-critical graphs.
Interlacing Eigenvalues in Time Reversible Markov Chains
Authors: Alfred Auslender, Marc Teboulle, Sami Ben-Tiba, Mark Brown
Venue: Mathematics of Operations Research (1999)

For irreducible, reversible, finite state chains we observe that two sets of eigenvalues related to the transition rate matrix Q; (&#955;0,...,&#955;m)and (&#947;1,..., &#947;m), are interlaced so that &#955;0 1 1 m m. Many quantities associated with L&#960;TA, the distribution of the first passage time to A starting in steady state, can be simply expressed in terms of these eigenvalues, and the interlacing property can be exploited to obtain approximations. There is a close connection between interlacing eigenvalues and completely monotone distributions, as well as a representation for finite mixtures of exponential distributions, which follow from this observation.