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Self-Adaptive and Self-Organizing Systems, 2007. SASO '07. First International Conference on

Date 9-11 July 2007

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  • First International Conference on Self-Adaptive and Self-Organizing Systems - Cover

    Page(s): c1
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  • First International Conference on Self-Adaptive and Self-Organizing Systems - Title

    Page(s): i - iii
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  • First International Conference on Self-Adaptive and Self-Organizing Systems - Copyright

    Page(s): iv
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  • First International Conference on Self-Adaptive and Self-Organizing Systems - Table of contents

    Page(s): v - viii
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  • Foreword from the General Co-chairs

    Page(s): ix
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  • Editorial by the Program Committee Co-Chairs

    Page(s): xi
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  • Steering Committee

    Page(s): xii
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  • Technical Meeting Committee

    Page(s): xiii
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  • Program Committee

    Page(s): xiv
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  • list-reviewer

    Page(s): xvi
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  • Michael G. Hinchey: Biological Inspiration.

    Page(s): xix
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    Greater understanding of biology in modern times has enabled significant breakthroughs in improving healthcare, quality of life, and eliminating many diseases and congenital illnesses. Simultaneously there is a move towards emulating nature and copying many of the wonders uncovered in biology, resulting in "biologically inspired" systems. Significant results have been reported in a wide range of areas, with systems inspired by nature enabling exploration, communication, and advances that were never dreamed possible just a few years ago. We warn, that as in many other fields of endeavor, we should be inspired by nature and biology, not engage in mimicry. We describe some results of biological inspiration that augur promise in terms of improving the safety and security of systems, and in developing self-managing systems that we hope will ultimately lead to self-governing systems. We concentrate on the concept of swarm-based exploration missions that will enable NASA to explore space more efficiently and collect data never before available to scientists. We discuss several new self-x properties that will make such missions possible and that will also have application in other areas. View full abstract»

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  • Gerald Jay Sussman: Designing for Applications Unanticipated by the Designer

    Page(s): xx
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    It is hard to build robust systems: systems that have acceptable behavior over a larger class of situations than was anticipated by their designers. The most robust systems are evolvable: they can be easily adapted to new situations with only minor modification. How can we design systems that are flexible in this way? View full abstract»

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  • Novel Mathematics-Inspired Algorithms for Self-Adaptive Peer-to-Peer Computing

    Page(s): 3 - 12
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB) |  | HTML iconHTML  

    This paper describes, and evaluates benefits of, a design methodology to translate certain mathematical models into the design of novel, self-adaptive, peer-to-peer (p2p) distributed computing algorithms ("protocols"). This methodology is potentially a good vehicle for translating natural phenomena, representable via mathematical models, into practical p2p protocols. Concretely, our first contribution is a set of techniques to translate certain discrete "sequence equations" rigorously into new p2p protocols called "sequence protocols". Sequence protocols are self-adaptive, scalable, and fault-tolerant, with applicability in p2p settings like grids. A sequence protocol is a set of probabilistic local and message-passing actions for each process. These actions are translated from terms in a set of source sequence equations. Without having each process simulate the source sequence equations, the emergent behavior of a sequence protocol in a p2p system is equivalent to, and predicted by, its source sequence equations. This paper's second contribution is a new self-adaptive grid computing protocol called "HoneyAdapt". HoneyAdapt is derived from sequence equations modeling adaptive bee foraging behavior in nature. HoneyAdapt is intended for grid applications that allow grid clients, at run-time, a choice of algorithms for executing chunks of the application's dataset. HoneyAdapt tells each grid client how to adaptively select at run-time, for each chunk it receives, a "good" algorithm for computing the chunk - this selection is based on continuous feedback from other clients. We present analysis, large-scale simulation results, and deployment results. View full abstract»

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  • Self-organizing Replica Placement - A Case Study on Emergence

    Page(s): 13 - 22
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3919 KB) |  | HTML iconHTML  

    The concept of self-organization is rapidly gaining importance in the area of distributed computing system However, we still lack the necessary means for engineering such system in a standardized way since their common properties are rather abstract, and the mechanisms from which self-organization emerges are too diverse. Therefore,it has become common practice to engineer computing systems by taking inspirations from well-known case studies of biological systems. However, the concepts found in such systems are in many cases only partially transferable to the domain of distributed computing systems since biological systems are subject to vastly different constraints compared to those in a computing system. Our contributions in this paper are the following: (i) We present a case study of a self-organizing software system that originates from the domain of distributed computing systems. Therefore, its concepts can be exploited in other distributed computing systems much more directly, (ii) We give a detailed analysis of the emergent properties of the system and the mechanisms by which they arise, (iii) We generalize the mechanisms by which self-organization emerges in this system and present a catalog of design questions that may help engineers in creating arbitrary self-organizing systems. View full abstract»

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  • A Space- and Time-Continuous Model of Self-Organizing Robot Swarms for Design Support

    Page(s): 23
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    Designing and implementing artificial self-organizing systems is a challenging task since they typically behave non- intuitive and only little theoretical foundations exist. Predicting a system of many components with a huge amount of interactions is beyond human skills. The currently common use of simulations for design support is not satisfying, as it is time-consuming and the results are most likely sub- optimal. In this work, we present the derivation of an analytical, time-, and space-continuous model for a swarm of autonomous robots based on the Fokker-Planck equation. While the motion model is in most parts physically motivated, the communication model is based on a heuristic approach. A showcase application to a recently proposed scenario of collective perception in a huge swarm of robots with very limited abilities is given and the simulation results are compared to the model. Despite the high level of abstraction, the prediction discrepancies are small and the parameters can be mapped one-to-one from the model to the control algorithm. Finally, we give an outlook on the capabilities of the proposed model, discuss its limitations, and suggest an improvement that could reduce the number of empirically determined parameters. View full abstract»

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  • A Nonlinear Multi-agent System designed for Swarm Intelligence: the Logistic MAS

    Page(s): 32 - 44
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (307 KB) |  | HTML iconHTML  

    Ant algorithms and flocking algorithms are the two main programming paradigms in swarm intelligence. They are built on stochastic models, widely used in optimization problems. However, though this modeling leads to high- performance algorithms, some mechanisms, like the symmetry break in ant decision, are still not well understood at the local ant level. Moreover, there is currently no modeling approach which joins the two paradigms. This paper proposes an entirely novel approach to the mathematical foundations of swarm algorithms: contrary to the current stochastic approaches, we show that an alternative deterministic model exists, which has its origin in deterministic chaos theory. We establish a reactive multi-agent system, based on logistic nonlinear decision maps, and designed according to the influence-reaction scheme. The rewriting of the decision functions leads to a new way of understanding the swarm phenomena in terms of state synchronization, and enables the analysis of their convergence behavior through bifurcation diagrams. We apply our approach on two concrete examples of each algorithm class, in order to demonstrate its general applicability. View full abstract»

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  • Text Display and Graphics Control on a Paintable Computer

    Page(s): 45 - 54
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (741 KB) |  | HTML iconHTML  

    Consider a display architecture where every pixel has its own dedicated graphics engine. Toward this end, we recast the rendering and graphics control of text for use on a paintable computer. Work on paintable computing is reviewed with a focus on the programming model based on autonomous, mobile code fragments (pfrags) which self-assemble into larger virtual structures. A device simulator is used to demonstrate pfrags interacting to form 2D coordinate scaffolds. Text characters, embodied as pfrag "seeds", use the scaffold to direct their migration and distribute models of the text and associated graphics code to the paint nodes. Affine transformations are demonstrated as an example of finely distributed graphics control. View full abstract»

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  • Neural Network of a Cognitive Crow: An interacting map based architecture

    Page(s): 55 - 64
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    Studies on animal reasoning can serve as a very relevant guide in building artificial systems that autonomously evolve their cognition and develop new skills in structural/functional coupling with their environments. New Caledonian crows display sophisticated abilities in fashioning tools and using them to acquire otherwise unobtainable food rewards. We may consider this an act of creativity, during which a cognitive agent reasons about things that do not yet exist but could exist as a result of his actions. However, the computational basis of such cognitive processes have remained elusive. Taking the example of tool manufacture by Caledonian crows, we explore an interacting self organizing map based architecture for virtually manipulating neural activity so as to achieve ones goals in novel situations. Simulation results demonstrate how interactions between sensorimotor space, action space and work space can be exploited in new situations to find action/action sequences that result in known intermediate states (sub goals) that in turn lead to the overall goal. View full abstract»

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  • Evolution of Cooperative Information Gathering in Self-Replicating Digital Organisms

    Page(s): 65 - 76
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    We describe a study in the application of digital evolution to the problem of cooperative information gathering. In digital evolution, self-replicating computer programs evolve to perform tasks and optimize resource usage in order to survive within a user defined computational environment. Instruction-level mutations during replication and CPU-cycle rewards for desired behavior produce natural selection within the population. The evolution is open-ended and not limited by human preconceptions. The contributions of this work are (1) to demonstrate that cooperative information gathering can evolve in digital organisms and (2) to provide insight into the fundamental processes governing evolution of such behavior. View full abstract»

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  • Firefly-inspired Heartbeat Synchronization in Overlay Networks

    Page(s): 77 - 86
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2257 KB) |  | HTML iconHTML  

    Heartbeat synchronization strives to have nodes in a distributed system generate periodic, local "heartbeat" events approximately at the same time. Many useful distributed protocols rely on the existence of such heartbeats for driving their cycle-based execution. Yet, solving the problem in environments where nodes are unreliable and messages are subject to delays and failures is non-trivial. We present a heartbeat synchronization protocol for overlay networks inspired by mathematical models of flash synchronization in certain species of fireflies. In our protocol, nodes send flash messages to their neighbors when a local heartbeat triggers. They adjust the phase of their next heartbeat based on incoming flash messages using an algorithm inspired by mathematical models of firefly synchronization. We report simulation results of the protocol in various realistic failure scenarios typical in overlay networks and show that synchronization emerges even when messages can have significant delay subject to large jitter. View full abstract»

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  • Desynchronization: The Theory of Self-Organizing Algorithms for Round-Robin Scheduling

    Page(s): 87 - 96
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    The study of synchronization has received much attention in a variety of applications, ranging from coordinating sensors in wireless networks to models of fireflies flashing in unison in biology. The inverse problem of desynchronization, however, has received little notice. Desynchronization is a powerful primitive: given a set of identical oscillators, applying a desynchronization primitive spreads them throughout the period, resulting in a round-robin schedule. This can be useful in several applications: medium access control in wireless sensor networks, designing fast analog- to-digital converters, and achieving high-throughput traffic intersections. Here we present two biologically-inspired algorithms for achieving desynchronization: DESYNC and INVERSE-MS. Both algorithms are simple and decentralized and are able to self-adjust to the addition and removal of agents. Furthermore, neither requires a global clock or explicit fault detection. We prove convergence, compute bounds for the running time, and assess the various tradeoffs. To our knowledge, the theory of self-organizing desynchronization algorithms is presented here for the first time. View full abstract»

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  • Clustering Distributed Energy Resources for Large-Scale Demand Management

    Page(s): 97 - 108
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB) |  | HTML iconHTML  

    Managing demand for electrical energy allows generation facilities to be run more efficiently. Current systems allow for management between large industrial consumers. There is, however, an increasing trend to decentralize energy resource management and push it to the level of individual households, or even appliances. In this work we investigate the suitability of using adaptive clustering to improve the scalability of decentralized energy resource management systems by appropriately partitioning resources. We review the area of distributed energy resource management and propose a simple yet realistic model to study the problem. Simulations using this model show that straightforward clustering and distributed planning methods allow systems to scale, but may be limited to only a few hundred- thousand appliances. Results indicate that there is an opportunity to apply adaptive clustering techniques in order to discover more advanced grouping criteria that would enable groups to change as appliances' behavior changes. The simulations further suggest that even an extremely limited exchange of information between clusters can greatly improve management solutions. View full abstract»

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  • Merging Intra-Planetary Index Structures: Decentralized Bootstrapping of Overlays

    Page(s): 109 - 118
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    Peer-to-peer index structures distributed and managed over the planet, commonly known as structured overlays (e.g., distributed hash tables), are posed to play the role of a fundamental building block for internet-scale distributed applications and information systems. One of the biggest impediment in realizing index distributed at intra-planetary scales is to be able to merge distinct indices that might have been constructed independently and separately, or have resulted from network partitions. By facilitating merger of such isolated index-structures, decentralized bootstrapping of structured overlays is made possible. We argue that such a self-organizational attribute of decentralized bootstrapping is of paramount importance for large scale systems. In this paper we provide algorithms and simulation based evaluation of merger of two tree-structured overlay networks. The experiments validate some intuitions, particularly we see how the merger operation can be carried out transparently from the end users in the sense that all keys that are accessible to any peer prior to the merger process continue to be accessible during and after the merger. Surprising at a first glance, we also observe that the overhead of data movement during merger of two overlays which originally partition the key-spaces arbitrarily is higher if there is more common content stored in the two networks. This counterintuitive behavior is on account of the fact that the assignment of partitions to peers change during the merger process, which in turn leads to movement of data. Since peers act based on local knowledge, the data already present in the other network is still unnecessarily moved, adding to the data transfer overhead. View full abstract»

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  • An Amortized Tit-For-Tat Protocol for Exchanging Bandwidth instead of Content in P2P Networks

    Page(s): 119 - 128
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    Incentives for resource sharing are crucial for the proper operation of P2P networks. The principle of the incentive mechanisms in current content sharing P2P networks such as BitTorrent is to have peers exchange content of mutual interest. As a consequence, a peer can actively participate in the system only if it shares content that is of immediate interest to other peers. In this paper we propose to lift this restriction by using bandwidth rather than content as the resource upon which incentives are based. Bandwidth, in contrast to content, is independent of peer interests and so can be exchanged between any two peers. We present the design of a protocol called amortized tit-for-tat (ATFT) based on the bandwidth-exchange concept. This protocol defines mechanisms for bandwidth exchange corresponding to those in BitTorrent for content exchange, in particular for finding bandwidth borrowers that amortize the bandwidth borrowed in the past with their currently idle bandwidth. In addition to the formally proven incentives for bandwidth contributions, ATFT provides natural solutions to the problems of peer bootstrapping, seeding incentive, peer link asymmetry, and anonymity, which have previously been addressed with much more complex designs. Experiments with a real-world dataset confirm that ATFT is efficient in enforcing bandwidth contributions and results in download performance better than provided by incentive mechanisms based on content exchange. View full abstract»

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  • Aggregation Dynamics in Service Overlay Networks

    Page(s): 129 - 140
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    In this work we analyze the characteristics of service overlay networks generated by uncoordinated service providers that deploy different service replicas on overlay nodes across the Internet. Our approach differs from previous works, that generally rely on application-level routing, in that we allow nodes to autonomously re-wire the service overlay to make it capable of absorbing a heterogeneously distributed workload that would otherwise result in some nodes with a specific service being overloaded and others remaining idle. We provide a game theoretic model of the overlay creation process and propose several optimization methods to achieve Nash equilibrium topologies. Equilibrium overlays are characterized by interconnected clusters of nodes that instantiate the same service replicas. Hindered by the computational complexity of finding stable wirings, we propose a simple distributed heuristic that allows the study of overlay networks with a realistic size and with several service instances. We show the ability of our re-wiring strategy to promote the emergence of a clustered global topology whilst running locally. We also argue that the lack of incentives for nodes to participate in the overlay creation might lead to several types of misbehavior, of which some representative cases are analyzed. Finally, both scalability and diversity (in terms of service instances) issues that might affect our distributed heuristic are evaluated in detail. View full abstract»

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