Dominik Fisch, Martin Jänicke, B. Sick, C. Müller-Schloer
The article addresses the phenomenon of emergence from a technical viewpoint. A technical system exhibits emergence when it has certain kinds of properties or qualities that are irreducible in the sense that they are not traceable to the constituent parts of the system. In particular, we show how emergence in technical systems can be detected and measured gradually using techniques from the field of probability theory and information theory. To detect or measure emergence we observe the system and extract characteristic attributes from those observations. As an extension of earlier work in the field, we propose emergence measures that are well-suited for continuous attributes (or hybrid attribute sets) using either non-parametric or model-based probability density estimation techniques. We also replace the known entropy-based emergence measures by divergence measures for probability densities (e.g., the Kullback-Leibler divergence or the Hellinger distance). We discuss advantages and drawbacks of these measures by means of some simulation experiments using artificial data sets and a real-world data set from the field of intrusion detection.
{"title":"Quantitative Emergence -- A Refined Approach Based on Divergence Measures","authors":"Dominik Fisch, Martin Jänicke, B. Sick, C. Müller-Schloer","doi":"10.1109/SASO.2010.31","DOIUrl":"https://doi.org/10.1109/SASO.2010.31","url":null,"abstract":"The article addresses the phenomenon of emergence from a technical viewpoint. A technical system exhibits emergence when it has certain kinds of properties or qualities that are irreducible in the sense that they are not traceable to the constituent parts of the system. In particular, we show how emergence in technical systems can be detected and measured gradually using techniques from the field of probability theory and information theory. To detect or measure emergence we observe the system and extract characteristic attributes from those observations. As an extension of earlier work in the field, we propose emergence measures that are well-suited for continuous attributes (or hybrid attribute sets) using either non-parametric or model-based probability density estimation techniques. We also replace the known entropy-based emergence measures by divergence measures for probability densities (e.g., the Kullback-Leibler divergence or the Hellinger distance). We discuss advantages and drawbacks of these measures by means of some simulation experiments using artificial data sets and a real-world data set from the field of intrusion detection.","PeriodicalId":370044,"journal":{"name":"2010 Fourth IEEE International Conference on Self-Adaptive and Self-Organizing Systems","volume":"98 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115506927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Designing and organising large numbers of autonomic resources into a coherent system is a difficult tendeavour. It necessitates handling complex interactions among dynamic, heterogeneous components, autonomic managers and human policies. Several architectural models have been proposed for organising these interactions. This paper focuses on a decentralised approach, while also considering two other possibilities – centralised and hierarchical. An architectural model is proposed and a prototype implementation with corresponding experimental results are subsequently presented and discussed.
{"title":"A Decentralised Architecture for Multi-objective Autonomic Management","authors":"Sylvain Frey, P. Lalanda, A. Diaconescu","doi":"10.1109/SASO.2010.34","DOIUrl":"https://doi.org/10.1109/SASO.2010.34","url":null,"abstract":"Designing and organising large numbers of autonomic resources into a coherent system is a difficult tendeavour. It necessitates handling complex interactions among dynamic, heterogeneous components, autonomic managers and human policies. Several architectural models have been proposed for organising these interactions. This paper focuses on a decentralised approach, while also considering two other possibilities – centralised and hierarchical. An architectural model is proposed and a prototype implementation with corresponding experimental results are subsequently presented and discussed.","PeriodicalId":370044,"journal":{"name":"2010 Fourth IEEE International Conference on Self-Adaptive and Self-Organizing Systems","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128357701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The design and implementation of distributed, self-organising and self-adaptive systems are challenging. This article details our experience gained during the development of self-organising assembly systems, which provide solutions for user-friendly agile manufacturing systems. More specifically, we describe how both a development method for self-organising systems, called MetaSelf, and the above particular application were progressively shaped, each influencing the other.
{"title":"Experience Report in Developing and Applying a Method for Self-Organisation to Agile Manufacturing","authors":"G. Serugendo, R. Frei","doi":"10.1109/SASO.2010.24","DOIUrl":"https://doi.org/10.1109/SASO.2010.24","url":null,"abstract":"The design and implementation of distributed, self-organising and self-adaptive systems are challenging. This article details our experience gained during the development of self-organising assembly systems, which provide solutions for user-friendly agile manufacturing systems. More specifically, we describe how both a development method for self-organising systems, called MetaSelf, and the above particular application were progressively shaped, each influencing the other.","PeriodicalId":370044,"journal":{"name":"2010 Fourth IEEE International Conference on Self-Adaptive and Self-Organizing Systems","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129036194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Harald Psaier, Lukasz Juszczyk, Florian Skopik, D. Schall, S. Dustdar
Mixed service-oriented systems composed of human actors and software services build up complex interaction networks. Without any coordination, such systems may exhibit undesirable properties due to unexpected behavior. Also, communications and interactions in such networks are not preplanned by top-down composition models. Consequently, the management of service-oriented applications is difficult due to changing interaction and behavior patterns that possibly contradict and result in faults from varying conditions and misbehavior in the network. In this paper we present a self-adaptation approach that regulates local interactions to maintain desired system functionality. To prevent degraded or stalled systems, adaptations operate by link modification or substitution of actors based on similarity and trust metrics. Unlike a security perspective on trust, we focus on the notion of socially inspired trust. We design an architecture based on two separate independent frameworks. One providing a real Web service test bed extensible for dynamic adaptation actions. The other is our self-adaptation framework including all modules required by systems with self-* properties. In our experiments we study a trust and similarity based adaptation approach by simulating dynamic interactions in the real Web services test bed.
{"title":"Runtime Behavior Monitoring and Self-Adaptation in Service-Oriented Systems","authors":"Harald Psaier, Lukasz Juszczyk, Florian Skopik, D. Schall, S. Dustdar","doi":"10.1109/SASO.2010.44","DOIUrl":"https://doi.org/10.1109/SASO.2010.44","url":null,"abstract":"Mixed service-oriented systems composed of human actors and software services build up complex interaction networks. Without any coordination, such systems may exhibit undesirable properties due to unexpected behavior. Also, communications and interactions in such networks are not preplanned by top-down composition models. Consequently, the management of service-oriented applications is difficult due to changing interaction and behavior patterns that possibly contradict and result in faults from varying conditions and misbehavior in the network. In this paper we present a self-adaptation approach that regulates local interactions to maintain desired system functionality. To prevent degraded or stalled systems, adaptations operate by link modification or substitution of actors based on similarity and trust metrics. Unlike a security perspective on trust, we focus on the notion of socially inspired trust. We design an architecture based on two separate independent frameworks. One providing a real Web service test bed extensible for dynamic adaptation actions. The other is our self-adaptation framework including all modules required by systems with self-* properties. In our experiments we study a trust and similarity based adaptation approach by simulating dynamic interactions in the real Web services test bed.","PeriodicalId":370044,"journal":{"name":"2010 Fourth IEEE International Conference on Self-Adaptive and Self-Organizing Systems","volume":"212 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121719391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In an open distributed system, computational resources are peer-owned, and distributed over time and space. The fact that these resources can dynamically join or leave the system (or can be discovered at runtime) leads to opportunities to carry out computations without statically owned resources, harnessing the collective compute power of the resources connected by the Internet. However, realizing this potential requires efficient and scalable resource discovery, coordination and control, not to mention that the dynamicity that makes opportunities visible at runtime also leads to uncertainty about continuous availability of the needed resources. In this paper, we present our experimental work using a resource-oriented temporal logic, ROTA, to reason about accommodating mobile distributed computations in an open system. Our results show that the approach leads to better accommodation of computations and scales well by avoiding unnecessary migrations.
{"title":"Self-Adaptive Resource Allocation in Open Distributed Systems","authors":"Xinghui Zhao, Nadeem Jamali","doi":"10.1109/SASO.2010.40","DOIUrl":"https://doi.org/10.1109/SASO.2010.40","url":null,"abstract":"In an open distributed system, computational resources are peer-owned, and distributed over time and space. The fact that these resources can dynamically join or leave the system (or can be discovered at runtime) leads to opportunities to carry out computations without statically owned resources, harnessing the collective compute power of the resources connected by the Internet. However, realizing this potential requires efficient and scalable resource discovery, coordination and control, not to mention that the dynamicity that makes opportunities visible at runtime also leads to uncertainty about continuous availability of the needed resources. In this paper, we present our experimental work using a resource-oriented temporal logic, ROTA, to reason about accommodating mobile distributed computations in an open system. Our results show that the approach leads to better accommodation of computations and scales well by avoiding unnecessary migrations.","PeriodicalId":370044,"journal":{"name":"2010 Fourth IEEE International Conference on Self-Adaptive and Self-Organizing Systems","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121918988","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As semiconductor technology approaches the atomic scale, electronic systems are increasingly burdened by physical variations and uncertainty. Traditionally-designed systems lack an ability to adapt to these fine-grained effects and are thus becoming more inefficient, error-prone, and subject to early wear out. This paper describes the paradigm of physically-adaptive computing (PAC), in which systems learn physical parameters and adapt with fine granularity in the field. We outline an architecture for an adaptation agent and investigate two key aspects of the adaptive process: self-characterization and physical self-optimization. A case study is presented involving random variations in latch reliability. We conducted experiments on a model of a PAC system with physical data obtained from actual field-programmable gate array (FPGA) hardware. Our results show that across 15 benchmark circuits the mean time between failures improved by an average of 30% via low-cost self-adaptation and by 45% assuming assistance from a remote server. Physical self-adaptation and assisted adaptation will both play an important role in achieving computational systems with atomic-scale features.
{"title":"Toward Physically-Adaptive Computing","authors":"K. Zick, J. Hayes","doi":"10.1109/SASO.2010.13","DOIUrl":"https://doi.org/10.1109/SASO.2010.13","url":null,"abstract":"As semiconductor technology approaches the atomic scale, electronic systems are increasingly burdened by physical variations and uncertainty. Traditionally-designed systems lack an ability to adapt to these fine-grained effects and are thus becoming more inefficient, error-prone, and subject to early wear out. This paper describes the paradigm of physically-adaptive computing (PAC), in which systems learn physical parameters and adapt with fine granularity in the field. We outline an architecture for an adaptation agent and investigate two key aspects of the adaptive process: self-characterization and physical self-optimization. A case study is presented involving random variations in latch reliability. We conducted experiments on a model of a PAC system with physical data obtained from actual field-programmable gate array (FPGA) hardware. Our results show that across 15 benchmark circuits the mean time between failures improved by an average of 30% via low-cost self-adaptation and by 45% assuming assistance from a remote server. Physical self-adaptation and assisted adaptation will both play an important role in achieving computational systems with atomic-scale features.","PeriodicalId":370044,"journal":{"name":"2010 Fourth IEEE International Conference on Self-Adaptive and Self-Organizing Systems","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127189894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present the Colored Power algorithm, which is designed to provide collaborative electricity demand shaping for residential and small-business customers. Demand shaping for this market sector is an important and challenging problem, since the vast number of such customers collectively account for a large fraction of total electricity consumption, yet each individual's consumption is small. Under the PACEM system, customers participate by "coloring" their appliances with a qualitative priority such as "can be shut off at peak power." Demand shaping for this system must be scalable to millions of appliances, operate quickly and fairly across customers, and act on any given appliance infrequently. This last constraint is particularly challenging: if an appliance that switches on or off must not be switched again for many minutes, then at any instant, a large fraction of appliances may not be controllable. The Colored Power algorithm addresses these challenges using randomized local actions. When the action distribution is adjusted to compensate for currently uncontrollable appliances, standard feedback controllers can be used to produce local actions that combine to create the desired global effect. Experiments in simulation verify that the algorithm provides fair control that is fast, scalable, and robust enough to be realistically deployable.
{"title":"Distributed Control for Small Customer Energy Demand Management","authors":"V. V. Ranade, J. Beal","doi":"10.1109/SASO.2010.21","DOIUrl":"https://doi.org/10.1109/SASO.2010.21","url":null,"abstract":"We present the Colored Power algorithm, which is designed to provide collaborative electricity demand shaping for residential and small-business customers. Demand shaping for this market sector is an important and challenging problem, since the vast number of such customers collectively account for a large fraction of total electricity consumption, yet each individual's consumption is small. Under the PACEM system, customers participate by \"coloring\" their appliances with a qualitative priority such as \"can be shut off at peak power.\" Demand shaping for this system must be scalable to millions of appliances, operate quickly and fairly across customers, and act on any given appliance infrequently. This last constraint is particularly challenging: if an appliance that switches on or off must not be switched again for many minutes, then at any instant, a large fraction of appliances may not be controllable. The Colored Power algorithm addresses these challenges using randomized local actions. When the action distribution is adjusted to compensate for currently uncontrollable appliances, standard feedback controllers can be used to produce local actions that combine to create the desired global effect. Experiments in simulation verify that the algorithm provides fair control that is fast, scalable, and robust enough to be realistically deployable.","PeriodicalId":370044,"journal":{"name":"2010 Fourth IEEE International Conference on Self-Adaptive and Self-Organizing Systems","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133115238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Juha-Matti Koljonen, M. Alava, M. Peltomäki, O. Tirkkonen
We consider generalized coloring of a weighted graph in a distributed setting, where each node in the graph is represented by an independent agent. The target is to minimize the weight of edges connecting same-color nodes. To avoid getting stuck in a not-too-good local optimum, we approach this problem by finding the colorable sub graph with the maximum weight subset of edges. The agents run a basic distributed graph coloring algorithm, and an algorithm for adding and removing edges, operating on different time scales. As basic distributed algorithms to color graphs we use distributed local search algorithms enabling plateau walks, together with a noise strategy to escape local minima. We evaluate performance in a setting inspired by self-organized resource allocation in a wireless network, and show that a distributed algorithm finding a colorable sub graph can outperform distributed greedy local search. As a related sub-problem, we investigate a procedure of adding edges to random planar graphs, keeping the color ability.
{"title":"Distributed Generalized Graph Coloring","authors":"Juha-Matti Koljonen, M. Alava, M. Peltomäki, O. Tirkkonen","doi":"10.1109/SASO.2010.10","DOIUrl":"https://doi.org/10.1109/SASO.2010.10","url":null,"abstract":"We consider generalized coloring of a weighted graph in a distributed setting, where each node in the graph is represented by an independent agent. The target is to minimize the weight of edges connecting same-color nodes. To avoid getting stuck in a not-too-good local optimum, we approach this problem by finding the colorable sub graph with the maximum weight subset of edges. The agents run a basic distributed graph coloring algorithm, and an algorithm for adding and removing edges, operating on different time scales. As basic distributed algorithms to color graphs we use distributed local search algorithms enabling plateau walks, together with a noise strategy to escape local minima. We evaluate performance in a setting inspired by self-organized resource allocation in a wireless network, and show that a distributed algorithm finding a colorable sub graph can outperform distributed greedy local search. As a related sub-problem, we investigate a procedure of adding edges to random planar graphs, keeping the color ability.","PeriodicalId":370044,"journal":{"name":"2010 Fourth IEEE International Conference on Self-Adaptive and Self-Organizing Systems","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116876137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Natural systems often exhibit, at a macro level, a tendency to order that emerges from simple and local interactions between the system components. This idea that the whole can denote a consistent behavior that is more than the sum of individual components has inspired the design and development of many artificial systems. Recently, with the pervasiveness of IT in the automation domain the application of such principles became interesting as a mean to developed seamlessly plug gable, robust and fault-tolerant mechatronic systems. These concepts, however, have been mainly applied from a control perspective. This paper argues the regulatory significance of diagnosis in such complex systems and discusses two strategies (fully centralized with global information and fully decentralized with local information) to perform a diagnostic analysis that explores the network dimension of future mechatronic systems.
{"title":"Global Vs Local: A Comparison of Two Approaches to Perform Diagnosis in Networks of Mechatronic Agents","authors":"L. Ribeiro, J. Barata, Bruno Alves, J. Ferreira","doi":"10.1109/SASO.2010.36","DOIUrl":"https://doi.org/10.1109/SASO.2010.36","url":null,"abstract":"Natural systems often exhibit, at a macro level, a tendency to order that emerges from simple and local interactions between the system components. This idea that the whole can denote a consistent behavior that is more than the sum of individual components has inspired the design and development of many artificial systems. Recently, with the pervasiveness of IT in the automation domain the application of such principles became interesting as a mean to developed seamlessly plug gable, robust and fault-tolerant mechatronic systems. These concepts, however, have been mainly applied from a control perspective. This paper argues the regulatory significance of diagnosis in such complex systems and discusses two strategies (fully centralized with global information and fully decentralized with local information) to perform a diagnostic analysis that explores the network dimension of future mechatronic systems.","PeriodicalId":370044,"journal":{"name":"2010 Fourth IEEE International Conference on Self-Adaptive and Self-Organizing Systems","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122277077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Seebach, Florian Nafz, Jan-Philipp Steghöfer, W. Reif
When introducing self-organization into a system, its developer aims to reduce the system’s complexity, during development as well as during operation. More often than not, the self-organization mechanism is ingenious, highly tweaked for the system under construction and not reproducible or reusable by other developers or in other projects. This paper introduces a software engineering guideline for self-organizing resource-flow systems along with an elaborated pattern that describes the elements of the system under construction and their collaboration. Together, guideline and pattern are the basis for a well-defined approach for the design and construction of systems in this class, which includes, among others, logistics applications, and adaptive production systems. They therefore allow developers to achieve reproducible results within a documented design framework, leverage the possibilities of the underlying formal approach and reuse self organization mechanisms tailored for the system class. The paper demonstrates the application of the guideline with a running example.
{"title":"A Software Engineering Guideline for Self-Organizing Resource-Flow Systems","authors":"H. Seebach, Florian Nafz, Jan-Philipp Steghöfer, W. Reif","doi":"10.1109/SASO.2010.26","DOIUrl":"https://doi.org/10.1109/SASO.2010.26","url":null,"abstract":"When introducing self-organization into a system, its developer aims to reduce the system’s complexity, during development as well as during operation. More often than not, the self-organization mechanism is ingenious, highly tweaked for the system under construction and not reproducible or reusable by other developers or in other projects. This paper introduces a software engineering guideline for self-organizing resource-flow systems along with an elaborated pattern that describes the elements of the system under construction and their collaboration. Together, guideline and pattern are the basis for a well-defined approach for the design and construction of systems in this class, which includes, among others, logistics applications, and adaptive production systems. They therefore allow developers to achieve reproducible results within a documented design framework, leverage the possibilities of the underlying formal approach and reuse self organization mechanisms tailored for the system class. The paper demonstrates the application of the guideline with a running example.","PeriodicalId":370044,"journal":{"name":"2010 Fourth IEEE International Conference on Self-Adaptive and Self-Organizing Systems","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130997800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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