Showing papers on "Modularity (networks) published in 1993"

Fbufs: a high-bandwidth cross-domain transfer facility

Abstract: We have designed and implemented a new operating system facility for I/O buffer management and data transferacross protection domain boundaries on shared memory machines. This facility, called fast buffers (fbufs), combines virtual page remapping with shared virtual memory, and exploits locality in I/O traffic to achieve high throughput without compromising protection, security, or modularity. goal is to help deliver the high bandwidth afforded by emerging high-speed networks to user-level processes, both in monolithic and microkernel-based operating systems.This paper outlines the requirements for a cross-domain transfer facility, describes the design of the fbuf mechanism that meets these requirements, and experimentally quantifies the impact of fbufs on network performance.

A superimposition control construct for distributed systems

Abstract: A control structure called a superimposition is proposed. The structure contains schematic abstractions of processes called roletypes in its declaration. Each roletype may be bound to processes from a basic distributed algorithm, and the operations of the roletype will then execute interleaved with those of the basic processes, over the same state space. This structure captures a kind of modularity natural for distributed programming, which previously has been treated using a macro-like implantation of code. The elements of a superimposition are identified, a syntax is suggested, correctness criteria are defined, and examples are presented

Image segmentation cues in motion processing: Implications for modularity in vision

Abstract: The problem of processing visual motion is underconstrained---many possible real world motions are compatible with any given dynamic retinal image. Recent psychophysical and neurophysiological experiments have shown that the primate visual system's normally veridical interpretation of moving patterns is attained through utilization of image segmentation cues unrelated to motion per se. These findings challenge notions of modularity in which it is assumed that the processing of specific scene properties, such as motion, can be studied in isolation from other visual processes. We discuss the implications of these findings with regard to both experimental and computational approaches to the study of visual motion.

An adaptive, object oriented strategy for base calling in DNA sequence analysis.

Abstract: An algorithm has been developed for the determination of nucleotide sequence from data produced in fluorescence-based automated DNA sequencing instruments employing the four-color strategy. This algorithm takes advantage of object oriented programming techniques for modularity and extensibility. The algorithm is adaptive in that data sets from a wide variety of instruments and sequencing conditions can be used with good results. Confidence values are provided on the base calls as an estimate of accuracy. The algorithm iteratively employs confidence determinations from several different modules, each of which examines a different feature of the data for accurate peak identification. Modules within this system can be added or removed for increased performance or for application to a different task. In comparisons with commercial software, the algorithm performed well.

An Improved Method for Constructing

Abstract: Research has shown that many communications pro- tocols exhibit multiple phases of behavior, performing a distinct function in each phase. A systematic method has been proposed by Chow, Gouda, and Lam for building multiphase protocols. By connecting several simpler protocols modeling the specific phases in a disciplined way, the newly constructed multiphase protocol enjoys the same correctness properties as the individual phases. The inherent modularity of the resultant protocol makes it easier to understand and analyze. However, the applicability of the existing method is subject to two rather stringent restrictions: the inability to handle message corruption or loss during phase transitions, and a rigid requirement on the selection of the points that connect different phases. This paper describes an improved method that either relaxes or eliminates the above restrictions. The construction of the Normal Response Mode of HDLC (High- level Data-Link Control) is presented to illustrate the use of this new method.

Some Modular Features of Temporal Cortex in Humans as Revealed by Pathological Changes in Alzheimer's Disease

Abstract: The concept of cortical modularity has surfaced as a generic term that alludes to any grouping or periodicity within the cerebral cortex relating to its neurons and their processes, and the enzymes, transmitters, and metabolic markers associated with them. Some of the best examples of anatomical modularity have been described in primary sensory areas such as the visual and somatosensory koniocortices. Functional examples of modularity abound in these same areas but may or may not have known morphological and chemical correlates. We depart from the traditional methods of cortical neuroanatomical analysis in this report and describe instead pathological alterations in the cortex in Alzheimer's disease. In particular, we focus on the cortex of the hippocampal formation and entorhinal, perirhinal, and anterior inferior temporal cortex and report findings that point toward a modular distribution of pathological changes unique to each of these cortical types. We argue that changes in modular organization as seen in Alzheimer's disease are in all likelihood germane to the abnormal function of each cortical area. These changes at the modular level may lie at the heart of the devastating behavioral breakdown in this illness, which can be severe even with limited pathology.

Incremental partial evaluation: the key to high performance, modularity and portability in operating systems

Abstract: The most prominent recent trend in operating system (OS) design has been the move towards micro-kernel based OS's [2, 8, 9, 12, 14]. Micro-kernel based OS's allow highlevel OS code to be structured as a collection of modules above a minimal kernel. Despite the many advantages of this modular approach, the performance overhead associated with existing modular implementations has proven to be a major liability in the commercial acceptance of these systems [3]. Finding a solution to the con ict between performance and modularity remains a critical research issue of practical importance. Contrary to popular belief, the micro-kernel approach to OS structuring does not lead to major improvements in portability. The modularity exhibited by most micro-kernel designs is coarse grained and orthogonal to the issue of localizing machine-dependent code. Some micro-kernel OS's do de ne various machine-independent interfaces within their micro-kernels, but these are unrelated to the system structuring mechanisms used in the higher layers of their OS code, and make a coarse-grained distinction between machinedependent and portable code [1, 11]. This coarse-grained approach limits portability by limiting the amount of code that can be reused. The state of the art in OS design can be summarized as follows. The vast majority of OS's in active use are monolithic, having traded portability and modularity for performance. There has been considerable research investment in micro-kernel OS's which o er some coarse-grained modularity at the expense of performance, and hence have not received high acceptance commercially. Neither monolithic kernels nor micro-kernels have made major progress towards true portability since they do not possess ne-grain modularity.

Experience with modularity in consul

Abstract: The use of modularity in the design and implementation of complex software simplifies the development process, as well as facilitating the construction of customized configurations. This paper describes our experience using modularity in Consul, a communication substrate used for constructing fault-tolerant distributed programs. First, Consul is presented as a case study of how modularity is feasible in both the design and the implementation of such systems. Secondly, general lessons about modularity in fault-tolerant systems based on our experience with Consul are given. Issues that are addressed include deciding how the system is divided into various modules, dealing with problems that result when protocols are combined, and ensuring that the underlying object infrastructure provides adequate support. The key observation is that the modularization process is most affected by dependencies between modules, both direct dependencies caused by one module explicitly using another's operation and indirect dependencies where one module is affected by another without direct interaction. Although our observations are based on designing and implementing Consul, the lessons are applicable to any fault-tolerant distributed system.

Completeness of Hierarchical Combinations of term Rewriting Systems

Abstract: In this paper, we propose a sufficient condition for modularity of completeness of hierarchical combinations. The sufficient condition is a syntactic one (about recursion) based on constructor discipline. Our result generalizes Middeldorp and Toyama's result on modularity of completeness for shared constructor systems.

Modularity of Termination and Confluence in Combinations of Rewrite Systems with lambda_omega

Abstract: We prove that termination and confluence are modular properties in combinations of the typed λ-calculus of order Ω with (first or higher order) term rewrite systems, provided that the first order rewrite system is conservative (non-duplicating) and the higher order rewrite system satisfies some suitable conditions (the general schema) and does not introduce critical pairs.

Incomplete Star Graph : An Economical Fault-tolerant Interconnection Network

Abstract: A number of existing multiprocessors are based on the hypercube interconnection network. The popularity of the hypercube is due to its small communication diameter, which grows logarithmically with the cube size, its fault-tolerant properties, and its modularity which makes it possible to build a larger cube from smaller subcubes. The star graph has been studied as a network topology for fault-tolerant parallel com puting. Unfortunately, the size of the network grows too sharply with n to be affordable for values of n larger than 7 or 8. We introduce a novel intercon nection network known as the incomplete star graph, which overcomes the above problem while retaining the most of the advantages of the star graph. We present the architecture of the incomplete star graph and compare its performance with the full star as well as competing architectures such as the incomplete hy? percube and arrangement graphs. We provide routing algorithms for both non-faulty and faulty incompletestar graphs, and study their performance.

A Three-phase Discrete Event Simulation with EPNSim Graphs

Abstract: In the simulation world view, there are three methods of constructing a simulation in common use: event scheduling, process orientation, and activity scanning (or three- phase approach). Because the three-phase approach has advantages of both modeling flexibility and modularity, we propose a simulation modeling tool, EPNSim, extended from the ordinary Petri Nets (PNs) to generate a language-independent pseudo code for the three-phase discrete simulation. Using the proposed method, the modeling processes of the three-phase discrete simulation can be concisely represented. In addition, it preserves the relative analytic properties of the original Petri net models (e.g. boundedness, liveliness, etc.), which are important for designing a system.

The principles of scalability and modularity in multiwavelength optical networks

Abstract: Two issues of primary importance in the design of optical networks are scalability and modularity. A scalable network is one to which more nodes may always be added; a modular network is one to which as few nodes may be added as is desired, one at a time, for example. Multiwavelength star and ring networks are not scalable because they require as many wavelengths as there are active node pairs on the network. In the simple fixed- wavelength-per-node address assignment the number of wavelengths required scales linearly with the number of nodes on the network. This is not acceptable for networks larger than a few tens of nodes. An implied requirement on scalable networks is, therefore, that the number of wavelengths required be independent of the number of nodes on the network.

Modularity in the design and implementation of Consul

Abstract: Consul is a system designed to support the use of fault-tolerance techniques in the construction of fault-tolerant distributed systems structured according to the state machine approach. The way in which modularity has been used in the design and implementation of Consul is described. The approach makes it easy to configure a system customized to the needs of a specific application and facilitates the development of the individual components that make up Consul. >

Category Theory for the Configuration of Complex Systems

Abstract: The abstract framework of category theory is shown to provide a precise semantics for the configuration of complex systems from their component parts Diagrams express configuration by representing the results of applying combinators to recursively defined system components Although modularity has been described as an essential property of complex systems, no clear and simple definition of a module has emerged at this general level In this paper a new module concept is defined to represent reusable system components, at any level of development

The Folded Petersen Network: A New Versatile Multiprocessor Interconnection Topology

Abstract: We introduce and analyze a new interconnection topology, called the n-folded Petersen network(F P n ), which is constructed by iteratively applying the cartesian product operation on the well-known Petersen graph itself. The FP n topology provides regularity, node- and edge-symmetry, optimal connectivity (and therefore maximal fault-tolerance), logarithmic diameter, modularity, and simple routing and broadcasting algorithms even in the presence of faults. With the same node-degree and connectivity, F P n has smaller diameter and accommodates more nodes than the 3n-dimensional binary hypercube.

Vertical migration of software functions and algorithms using enhanced microsequencing

Abstract: A scheme for vertical migration of algorithms and functions with complex sequencing structure from software through firmware into microcoded VLSI structures is discussed. The expected benefits of migration are gains in speed, reliability, and stability. The scheme employs a migration model that is based on microcode modularity and is supported by a hardware microcontroller with enhanced sequencing capability. The basic idea is to capture, using effective compilation techniques, the explicit or implicit sequencing structure of a function. Migration is then effected by sequencing calls into a library of microcode modules of a target machine architecture. The modularity of the migration system is well suited for generating VLSI microcode. The experimental results from an environment consisting of several firmware development tools show substantial time performance improvements in comparison to software implementations. Comparisons to traditional migration approaches indicate that the proposed scheme is faster and requires less memory space for the migration of software algorithms into firmware. >

Cooperation and modularity for classification through neural network techniques

Abstract: We study modularity in the frame of neural network systems on two real-size applications. The cooperation of performant modules is used to improve recognition and rejection rates of handwritten digits coming from postal zip-codes. From a multi-class problem in multi-font character recognition, we have designed 49 neural submodules (one per class), and different cooperation schemes are studied and compared. The relation between the quality of the expert system and the efficiency of the cooperation scheme is shown. >

Currents in connectionism

Abstract: This paper reviews four significant advances on the feedforward architecture that has dominated discussions of connectionism. The first involves introducing modularity into networks by employing procedures whereby different networks learn to perform different components of a task, and a Gating Network determines which network is best equiped to respond to a given input. The second consists in the use of recurrent inputs whereby information from a previous cycle of processing is made available on later cycles. The third development involves developing compressed representations of strings in which there is no longer an explicit encoding of the components but where information about the structure of the original string can be recovered and so is present functionally. The final advance entails using connectionist learning procedures not just to change weights in networks but to change the patterns used as inputs to the network. These advances significantly increase the usefulness of connectionist networks for modeling human cognitive performance by, among other things, providing tools for explaining the productivity and systematicity of some mental activities, and developing representations that are sensitive to the content they are to represent.

Quantum logic requires weak modularity

Abstract: The spirit of quantum logic cannot be extended to systems, such as separated quantum entities, which do not satisfy the axiom of weak modularity. This is because the implication relation has no definite equational characterisation in such systems

URANO: An Object-Oriented Artificial Neural Network Simulation Tool

Abstract: A highly flexible environment has been developed based on the object-oriented paradigm for modelling artificial neural networks (ANNs). This paper propose a hierarchy of classes that models ANN. The design of the hierarchy is characterized by a high degree of modularity, based on parametrizable data structures and autonomous modules. Composition rules of structures and methods enable to build, step by step, more complex structures from simple ones previously defined. One of the most relevant benefits obtained from using an object-oriented approach is related with the definition of multi-networks. URANO (Universe of ANN Object oriented) is a powerful software tool developed using the C++ programming language for building and using prototypes of ANNs in which inherited mechanism can be used for building new ANNs from already existing ones. It is easy to work with and its effectiveness and efficiency have been proven by applications.

New modular architectures for regular multihop lightwave networks

Abstract: By using WDM channels and tunable transceivers, arbitrary virtual topologies can be mapped onto physical-topology optical networks. Regular connectivity patterns with small nodal degree, simple routing, and small network diameter are attractive candidates for logical topologies. ShuffleNet1 and de Bruijn graph2,3 are two such networks, but they are not easily scalable. For example, ShuffleNet and de Bruijn graph must have KP“and P’ nodes, respectively, where D,P= 2, 3,…, and K = 1, 2, 3, .… We propose two new network architectures, GEMNET and MRNET, that are modular and scalable. The modularity of these networks equals the nodal degree P, and generally they both have properties comparable to or better than de Bruijn graph, ShuffleNet, and Manhattan Street Network.4 GEMNET is based on a generalized shuffle-exchange connectivity pattern,4 and MRNET is based on a modification of RegularNet5 for simplified routing. Formal descriptions of GEMNET and MRNET and the comparative performance of various regular multihop network architectures are given below. However, derivations are omitted to conserve space.

Modularity for Logic Programs

Abstract: We present a module concept for logic programming with formal interfaces, motivated by work in algebraic specification. We discuss aspects of semantics and correctness of such modules. Further we describe how to build larger logic programs from single modules by so called module operations, and derive results concerning compositionality of semantics and correctness preservation.

Fast and reliable fault analysis in complex power systems

Abstract: Neural network approaches to the design of diagnosis systems for electrical networks have to cope with serious problems derived from the large size of such systems, which makes modularity the obvious solution. A modular approach which is based on functional criteria and provides scalability and adaptability to topological changes is presented. The hypotheses generated by the neural system are justified by a competitive system which detects simple or simultaneous disturbances. This approach allows for a parallel, distributed implementation. >