Página 1 dos resultados de 32416 itens digitais encontrados em 0.071 segundos

Análise do surgimento de polos de ocupação urbana à ótica de Sistemas Complexos; Analysis of the emergence of urban occupation centers by Complex Systems Approach

Duran Junior, Laerte Jose
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 05/10/2012 Português
Relevância na Pesquisa
66.715425%
Desde os primeiros anos do século XXI mais da metade da população mundial passou a habitar em regiões urbanas. Este processo de urbanização, acelerado a partir da revolução industrial, trouxe consigo benefícios inegáveis à humanidade, mas também possui externalidades evidentes como o congestionamento, a violência e a segregação. Preocupada com estes problemas, surge a ciência do planejamento urbano, ora atuando na antecipação dos fatos, ora remediando os problemas existentes, utilizando as mais variadas propostas que partem de correntes de pensamento compostas por estudiosos das cidades que, nesta difícil tarefa, procuram embasamento em experiências anteriores ou em estudos que invariavelmente envolvem outras áreas de conhecimento, como sociologia, economia e engenharia. Paralelamente a estes esforços, surge nos últimos 40 anos, outra área de conhecimento, denominada Sistemas Complexos, para estudar fenômenos físicos, biológicos, econômicos e sociais, entre outros, utilizando as técnicas provenientes da dinâmica não linear, da física estatística e da computação baseada em agentes, e que vem sendo progressivamente aplicada ao estudo das cidades. Neste trabalho é realizada uma breve revisão da história do surgimento e da evolução das cidades...

Mineração de dados em redes complexas: estrutura e dinâmica; Data mining in complex networks: structure and dynamics

Arruda, Guilherme Ferraz de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 02/04/2013 Português
Relevância na Pesquisa
56.715425%
A teoria das redes complexas é uma área altamente interdisciplinar que oferece recursos para o estudo dos mais variados tipos de sistemas complexos, desde o cérebro até a sociedade. Muitos problemas da natureza podem ser modelados como redes, tais como: as interações protéicas, organizações sociais, o mercado financeiro, a Internet e a World Wide Web. A organização de todos esses sistemas complexos pode ser representada por grafos, isto é, vértices conectados por arestas. Tais topologias têm uma influencia fundamental sobre muitos processos dinâmicos. Por exemplo, roteadores altamente conectados são fundamentais para manter o tráfego na Internet, enquanto pessoas que possuem um grande número de contatos sociais podem contaminar um grande número de outros indivíduos. Ao mesmo tempo, estudos têm mostrado que a estrutura do cérebro esta relacionada com doenças neurológicas, como a epilepsia, que está ligada a fenômenos de sincronização. Nesse trabalho, apresentamos como técnicas de mineração de dados podem ser usadas para estudar a relação entre topologias de redes complexas e processos dinâmicos. Tal estudo será realizado com a simulação de fenômenos de sincronização, falhas, ataques e propagação de epidemias. A estrutura das redes será caracterizada através de métodos de mineração de dados...

Sistemas computacionais bio-inspirados : sintese e aplicação em inteligencia computacional e homeostase artificial; Bioinspired computing systems : synthesis and application in computational intelligence and artificial homeostasis

Patricia Amancio Vargas
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 05/04/2005 Português
Relevância na Pesquisa
56.75722%
Este trabalho propõe uma classificação circunstancial para sistemas complexos, incluindo uma estrutura unificada de descrição a ser empregada na análise e síntese de sistemas computacionais bio-inspirados. Como um ramo dos sistemas complexos organizados, os sistemas computacionais bio-inspirados admitem uma sub-divisão em sistemas de inteligência computacional e sistemas homeostáticos artificiais. Com base neste formalismo, duas abordagens híbridas são concebidas e aplicadas em problemas de navegação autônoma de robôs. A primeira abordagem envolve sistemas classificadores com aprendizado e sistemas imunológicos artificiais, visando explorar conjuntamente conceitos intrínsecos a sistemas complexos, como auto-organização, evolução e cognição dinâmica. Fundamentada nas interações neuro-imuno-endócrinas do corpo humano, a segunda abordagem propõe um novo modelo de sistema homeostático artificial, explorando mudanças de contexto e efeitos do meio sobre o comportamento autônomo de um robô móvel. Embora preliminares, os resultados obtidos envolvem simulação computacional em ambientes virtuais e alguns experimentos com robôs reais, permitindo extrair conclusões relevantes acerca do potencial das abordagens propostas e abrindo perspectivas para a síntese de sistemas complexos adaptativos de interesse prático; This work proposes a circumstantial classification for complex systems...

Computational shelf-life dating : complex systems approaches to food quality and safety

Martins, Rui C.; Lopes, Vítor V.; Vicente, A. A.; Teixeira, J. A.
Fonte: Springer Science Publicador: Springer Science
Tipo: Artigo de Revista Científica
Publicado em /09/2008 Português
Relevância na Pesquisa
66.636514%
Shelf-life is defined as the time that a product is acceptable and meets the consumers expectations regarding food quality. It is the result of the conjunction of all services in production, distribution, and consumption. Shelf-life dating is one of the most difficult tasks in food engineering. Market pressure has lead to the implementation of shelf-life by sensory analyses, which may not reflect the full quality spectra. Moreover, traditional methods for shelf-life dating and small-scale distribution chain tests cannot reproduce in a laboratory the real conditions of storage, distribution, and consumption on food quality. Today, food engineers are facing the challenges to monitor, diagnose, and control the quality and safety of food products. The advent of nanotechnology, multivariate sensors, information systems, and complex systems will revolutionize the way we manage, distribute, and consume foods. The informed consumer demands foods, under the legal standards, at low cost, high standards of nutritional, sensory, and health benefits. To accommodate the new paradigms, we herein present a critical review of shelf-life dating approaches with special emphasis in computational systems and future trends on complex systems methodologies applied to the prediction of food quality and safety.; Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BPD/26133/2005...

Complex networks and data mining: toward a new perspective for the understanding of complex systems

Zanin, Massimiliano
Fonte: Universidade Nova de Lisboa Publicador: Universidade Nova de Lisboa
Tipo: Tese de Doutorado
Publicado em /12/2014 Português
Relevância na Pesquisa
66.75556%
Complex systems, i.e. systems composed of a large set of elements interacting in a non-linear way, are constantly found all around us. In the last decades, different approaches have been proposed toward their understanding, one of the most interesting being the Complex Network perspective. This legacy of the 18th century mathematical concepts proposed by Leonhard Euler is still current, and more and more relevant in real-world problems. In recent years, it has been demonstrated that network-based representations can yield relevant knowledge about complex systems. In spite of that, several problems have been detected, mainly related to the degree of subjectivity involved in the creation and evaluation of such network structures. In this Thesis, we propose addressing these problems by means of different data mining techniques, thus obtaining a novel hybrid approximation intermingling complex networks and data mining. Results indicate that such techniques can be effectively used to i) enable the creation of novel network representations, ii) reduce the dimensionality of analyzed systems by pre-selecting the most important elements, iii) describe complex networks, and iv) assist in the analysis of different network topologies. The soundness of such approach is validated through different validation cases drawn from actual biomedical problems...

Statistical Learning of Some Complex Systems: From Dynamic Systems to Market Microstructure

Tong, Xiao Thomas
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation
Português
Relevância na Pesquisa
56.71164%
A complex system is one with many parts, whose behaviors are strongly dependent on each other. There are two interesting questions about complex systems. One is to understand how to recover the true structure of a complex system from noisy data. The other is to understand how the system interacts with its environment. In this thesis, we address these two questions by studying two distinct complex systems: dynamic systems and market microstructure. To address the first question, we focus on some nonlinear dynamic systems. We develop a novel Bayesian statistical method, Gaussian Emulator, to estimate the parameters of dynamic systems from noisy data, when the data are either fully or partially observed. Our method shows that estimation accuracy is substantially improved and computation is faster, compared to the numerical solvers. To address the second question, we focus on the market microstructure of hidden liquidity. We propose some statistical models to explain the hidden liquidity under different market conditions. Our statistical results suggest that hidden liquidity can be reliably predicted given the visible state of the market.; Statistics

Towards a Theory of Complicatedness: Framework for Complex Systems Analysis and Design

Tang, Victor; Salminen, Vesa
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Trabalho em Andamento Formato: 251553 bytes; application/pdf
Português
Relevância na Pesquisa
66.83181%
Global, dynamic, and competitive business environment has increased the complexity in product, service, operational processes and human side. Much engineering effort goes into reducing systems complexity. We argue that the real issue is reducing complicatedness. This is an important distinction. Complexity can be a desirable property of systems provided it is architected complexity that reduces complicatedness. Complexity and complicatedness are not synonyms. Complexity is an inherent property of systems; complicatedness is a derived function of complexity. We introduce the notion of complicatedness of complex systems, present equations for each and show they are separate and distinct properties. To make these ideas actionable, we present a design methodology to address complicatedness. We show examples and discuss how our equations reflect the fundamental behavior of complex systems and how our equations are consistent with our intuition and system design experience. We discuss validation experiments with global firms and address potential areas for further research. We close with a discussion of the implications for systems design engineers. As engineers, we believe our strongest contributions are to the analysis, design, and managerial practice of complex systems analysis and design. We illustrate the difference between complexity and complicatedness. Relative to a manual transmission...

Complex System Classification

Magee, Christopher; de Weck, Olivier
Fonte: International Council On Systems Engineering (INCOSE) Publicador: International Council On Systems Engineering (INCOSE)
Tipo: Trabalho em Andamento Formato: 428544 bytes; application/msword
Português
Relevância na Pesquisa
66.73268%
The use of terms such as “Engineering Systems”, “System of systems” and others have been coming into greater use over the past decade to denote systems of importance but with implied higher complexity than for the term systems alone. This paper searches for a useful taxonomy or classification scheme for complex Systems. There are two aspects to this problem: 1) distinguishing between Engineering Systems (the term we use) and other Systems, and 2) differentiating among Engineering Systems. Engineering Systems are found to be differentiated from other complex systems by being human-designed and having both significant human complexity as well as significant technical complexity. As far as differentiating among various engineering systems, it is suggested that functional type is the most useful attribute for classification differentiation. Information, energy, value and mass acted upon by various processes are the foundation concepts underlying the technical types.; Engineering Systems Division and Mechanical Engineering, Center for Innovation in Product Development

A complex systems approach to important biological problems.

Berryman, Matthew John
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 319443 bytes; 2941665 bytes; 344632 bytes; application/pdf; application/pdf; application/pdf
Publicado em //2007 Português
Relevância na Pesquisa
66.79075%
Complex systems are those which exhibit one or more of the following inter-related behaviours: 1. Nonlinear behaviour: the component parts do not act in linear ways, that is the superposition of the actions of the parts is not the output of the system. 2. Emergent behaviour: the output of the system may be inexpressible in terms of the rules or equations of the component parts. 3. Self-organisation: order appears from the chaotic interactions of individuals and the rules they obey. 4. Layers of description: in which a rule may apply at some higher levels of description but not at lower layers. 5. Adaptation: in which the environment becomes encoded in the rules governing the structure and/or behaviour of the parts (in this case strictly agents) that undergo selection in which those that are by some measure better become more numerous than those that are not as “fit”. A single cell is a complex system: we cannot explain all of its behaviour as simply the sum of its parts. Similarly, DNA structures, social networks, cancers, the brain, and living beings are intricate complex systems. This thesis tackles all of these topics from a complex systems approach. I have skirted some of the philosophical issues of complex systems and mainly focussed on appropriate tools to analyse these systems...

Education in Complex Systems for Systems Engineers [Paper and Presentation included] [NDIA 15th Annual Systems Engineering Conference, Paper 14597]

Miller, Gregory A.
Fonte: Escola de Pós-Graduação Naval Publicador: Escola de Pós-Graduação Naval
Tipo: Presentation; Working Paper
Português
Relevância na Pesquisa
66.653877%
Attached is a paper as well as a presentation - - Note that this presentation came from this conference: 15th ANNUAL SYSTEMS ENGINEERING CONFERENCE, OCTOBER 22 - 25, 2012, SAN DIEGO, CA More information is here: http://www.dtic.mil/ndia/2012system/; This paper explores the potential benefits and disadvantages associated with providing a course (or part of a course) in complex systems as part of a systems engineering graduate degree program. An overview of systems engineering education programs and a history of SE curricular design provides context for this exploration. Curriculums other than systems engineering that include courses in complexity, nonlinear dynamics, emergence, chaos, decentralized synchronization through stigmergy, scale-free networks and related topics are also examined. The application of these concepts to design problems is assessed, particularly for engineers in the defense domain. Complex systems learning objectives tailored for systems engineers are proposed. Finally, a framework on which to base a trade-off analysis to determine if such topics should be included in an existing or developing graduate degree program is recommended.

Managing large and complex systems with Omnispective Analysis and Reasoning

Chemboli, Srinivas; Boughton, Clive
Fonte: Engineers Australia; http://www.engineersaustralia.org.au/ Publicador: Engineers Australia; http://www.engineersaustralia.org.au/
Tipo: Conference paper; Accepted Version Formato: 15 pages
Português
Relevância na Pesquisa
56.71805%
Development of newer and more sustainable systems requires a thorough understanding of the complex interactions in current systems. Therefore it is necessary to be able to switch between detailed knowledge of component systems and an overall appraisal of the entire system. Current efforts to develop ontologies capturing a "complete" and "universal" understanding of entire systems of systems often result in loss of depth and precision of knowledge contained in the participating systems. This further adds to the uncertainty and intractability in the management of the complex system. In addition, the absence of a single control and execution context makes it difficult to validate the system against desired intent and goals. All of these increase the likelihood of cost, effort and development time overruns in maintaining, enhancing, retiring and replacing systems. In this paper, we propose a novel approach to address these concerns by the application of Omnispective Analysis and Reasoning (OAR), an epistemic framework for managing intellectual concerns. By creating "localized ontologies" for capturing the ’silos’ of knowledge in component systems, we develop artifacts for only those concerns from the participating domains that are identified as relevant. These localized ontologies can unambiguously capture all relevant system artifacts with valuable information about their context of application within the system. With the OAR framework...

General and craniofacial development are complex adaptive processes influenced by diversity

Brook, A.H.; O'Donnell, M.B.; Hone, A.; Hart, E.; Hughes, T.E.; Smith, R.N.; Townsend, G.C.
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Relevância na Pesquisa
56.74553%
Complex systems are present in such diverse areas as social systems, economies, ecosystems and biology and, therefore, are highly relevant to dental research, education and practice. A Complex Adaptive System in biological development is a dynamic process in which, from interacting components at a lower level, higher level phenomena and structures emerge. Diversity makes substantial contributions to the performance of complex adaptive systems. It enhances the robustness of the process, allowing multiple responses to external stimuli as well as internal changes. From diversity comes variation in outcome and the possibility of major change; outliers in the distribution enhance the tipping points. The development of the dentition is a valuable, accessible model with extensive and reliable databases for investigating the role of complex adaptive systems in craniofacial and general development. The general characteristics of such systems are seen during tooth development: self-organization; bottom-up emergence; multitasking; self-adaptation; variation; tipping points; critical phases; and robustness. Dental findings are compatible with the Random Network Model, the Threshold Model and also with the Scale Free Network Model which has a Power Law distribution. In addition...

Methods and Techniques of Complex Systems Science: An Overview

Shalizi, Cosma Rohilla
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
56.724146%
In this chapter, I review the main methods and techniques of complex systems science. As a first step, I distinguish among the broad patterns which recur across complex systems, the topics complex systems science commonly studies, the tools employed, and the foundational science of complex systems. The focus of this chapter is overwhelmingly on the third heading, that of tools. These in turn divide, roughly, into tools for analyzing data, tools for constructing and evaluating models, and tools for measuring complexity. I discuss the principles of statistical learning and model selection; time series analysis; cellular automata; agent-based models; the evaluation of complex-systems models; information theory; and ways of measuring complexity. Throughout, I give only rough outlines of techniques, so that readers, confronted with new problems, will have a sense of which ones might be suitable, and which ones definitely are not.; Comment: 96 pages, 8 figures. Versions 2 and 3: corrects minor typographical errors. Version 4: Expanded examples, updated references (through late 2004), matches published version up to changes in formatting

Mixing, Ergodicity and the Fluctuation-Dissipation Theorem in complex systems

Vainstein, M. H.; Costa, I. V. L.; Oliveira, F. A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/01/2005 Português
Relevância na Pesquisa
56.734756%
Complex systems such as glasses, gels, granular materials, and systems far from equilibrium exhibit violation of the ergodic hypothesis (EH) and of the fluctuation-dissipation theorem (FDT). Recent investigations in systems with memory have established a hierarchical connection between mixing, the EH and the FDT. They have shown that a failure of the mixing condition (MC) will lead to the subsequent failures of the EH and of the FDT. Another important point is that such violations are not limited to complex systems: simple systems may also display this feature. Results from such systems are analytical and obviously easier to understand than those obtained in complex structures, where a large number of competing phenomena are present. In this work, we review some important requirements for the validity of the FDT and its connection with mixing, the EH and anomalous diffusion in one-dimensional systems. We show that when the FDT fails, an out-of-equilibrium system relaxes to an effective temperature different from that of the heat reservoir. This effective temperature is a signature of metastability found in many complex systems such as spin-glasses and granular materials.; Comment: to be published in the Proceedings of the XIX Sitges Conference on ''Jammming...

Complex Systems + Systems Engineering = Complex Systems Engineeri

Abbott, Russ
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/03/2006 Português
Relevância na Pesquisa
56.82153%
One may define a complex system as a system in which phenomena emerge as a consequence of multiscale interaction among the system's components and their environments. The field of Complex Systems is the study of such systems--usually naturally occurring, either bio-logical or social. Systems Engineering may be understood to include the conceptualising and building of systems that consist of a large number of concurrently operating and interacting components--usually including both human and non-human elements. It has become increasingly apparent that the kinds of systems that systems engineers build have many of the same multiscale characteristics as those of naturally occurring complex systems. In other words, systems engineering is the engineering of complex systems. This paper and the associated panel will explore some of the connections between the fields of complex systems and systems engineering.; Comment: 10 pages. Position paper to be presented at Conference on Systems Engineering Research

Description of Complex Systems in terms of Self-Organization Processes of Prime Integer Relations

Korotkikh, Victor; Korotkikh, Galina
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
56.76132%
In the paper we present a description of complex systems in terms of self-organization processes of prime integer relations. A prime integer relation is an indivisible element made up of integers as the basic constituents following a single organizing principle. The prime integer relations control correlation structures of complex systems and may describe complex systems in a strong scale covariant form. It is possible to geometrize the prime integer relations as two-dimensional patterns and isomorphically express the self-organization processes through transformations of the geometric patterns. As a result, prime integer relations can be measured by corresponding geometric patterns specifying the dynamics of complex systems. Determined by arithmetic only, the self-organization processes of prime integer relations can describe complex systems by information not requiring further explanations. This gives the possibility to develop an irreducible theory of complex systems.; Comment: 8 pages, 4 figures, index corrected, minor changes mainly of stylistic character

Challenges in Complex Systems Science

Miguel, Maxi San; Johnson, Jeffrey H.; Kertesz, Janos; Kaski, Kimmo; Díaz-Guilera, Albert; MacKay, Robert S.; Loreto, Vittorio; Erdi, Peter; Helbing, Dirk
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 22/04/2012 Português
Relevância na Pesquisa
56.75087%
FuturICT foundations are social science, complex systems science, and ICT. The main concerns and challenges in the science of complex systems in the context of FuturICT are laid out in this paper with special emphasis on the Complex Systems route to Social Sciences. This include complex systems having: many heterogeneous interacting parts; multiple scales; complicated transition laws; unexpected or unpredicted emergence; sensitive dependence on initial conditions; path-dependent dynamics; networked hierarchical connectivities; interaction of autonomous agents; self-organisation; non-equilibrium dynamics; combinatorial explosion; adaptivity to changing environments; co-evolving subsystems; ill-defined boundaries; and multilevel dynamics. In this context, science is seen as the process of abstracting the dynamics of systems from data. This presents many challenges including: data gathering by large-scale experiment, participatory sensing and social computation, managing huge distributed dynamic and heterogeneous databases; moving from data to dynamical models, going beyond correlations to cause-effect relationships, understanding the relationship between simple and comprehensive models with appropriate choices of variables, ensemble modeling and data assimilation...

Increase of Organization in Complex Systems

Georgiev, Georgi Yordanov; Daly, Michael; Gombos, Erin; Vinod, Amrit; Hoonjan, Gajinder
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 26/01/2013 Português
Relevância na Pesquisa
56.76132%
Measures of complexity and entropy have not converged to a single quantitative description of levels of organization of complex systems. The need for such a measure is increasingly necessary in all disciplines studying complex systems. To address this problem, starting from the most fundamental principle in Physics, here a new measure for quantity of organization and rate of self-organization in complex systems based on the principle of least (stationary) action is applied to a model system - the central processing unit (CPU) of computers. The quantity of organization for several generations of CPUs shows a double exponential rate of change of organization with time. The exact functional dependence has a fine, S-shaped structure, revealing some of the mechanisms of self-organization. The principle of least action helps to explain the mechanism of increase of organization through quantity accumulation and constraint and curvature minimization with an attractor, the least average sum of actions of all elements and for all motions. This approach can help describe, quantify, measure, manage, design and predict future behavior of complex systems to achieve the highest rates of self organization to improve their quality. It can be applied to other complex systems from Physics...

Network Dynamics and Systems Biology

Norrell, Johannes Adrie
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação Formato: 2947765 bytes; application/pdf
Publicado em //2009 Português
Relevância na Pesquisa
56.779062%

The physics of complex systems has grown considerably as a field in recent decades, largely due to improved computational technology and increased availability of systems level data. One area in which physics is of growing relevance is molecular biology. A new field, systems biology, investigates features of biological systems as a whole, a strategy of particular importance for understanding emergent properties that result from a complex network of interactions. Due to the complicated nature of the systems under study, the physics of complex systems has a significant role to play in elucidating the collective behavior.

In this dissertation, we explore three problems in the physics of complex systems, motivated in part by systems biology. The first of these concerns the applicability of Boolean models as an approximation of continuous systems. Studies of gene regulatory networks have employed both continuous and Boolean models to analyze the system dynamics, and the two have been found produce similar results in the cases analyzed. We ask whether or not Boolean models can generically reproduce the qualitative attractor dynamics of networks of continuously valued elements. Using a combination of analytical techniques and numerical simulations...

Integrated water resource management in complex systems: how the catchment management strategies seek to achieve sustainability and equity in water resources in South Africa

Pollard,Sharon; du Toit,Derick
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 Português
Relevância na Pesquisa
66.763047%
It is increasingly evident amongst practitioners and academics alike that the management approaches of the past have failed to deal adequately with the challenges posed by complex and rapidly changing systems. Indeed the call for integrated approaches such as those embodied in integrated water resource management (IWRM) reflects such concerns. This is because these systems are characterised by complexity in which an understanding of linkages, multiple drivers and unpredictable outcomes is critical. It is also widely recognised that the management of such systems requires an iterative, 'learning-by-doing' approach that is reflexive in nature and builds learning into the next management cycle. We suggest that any attempt to define and implement viable and effective governance of water resources, as well as rehabilitation measures, requires understanding that catchments are complex systems showing the aforementioned characteristics. As a corollary, an adaptive management approach appears best suited to such conditions. In this paper we argue that South Africa's highly-acclaimed National Water Act and associated policy documents such as the National Water Resource Strategy is an example of a policy document that reflects this thinking...