CiteULike: Tag emergent

Sharp Transition towards Shared Vocabularies in Multi-Agent Systems

A Baronchelli — 2005-10-26T09:44:21-00:00

(9 Sep 2005)

What processes can explain how very large populations are able to converge on the use of a particular word or grammatical construction without global coordination? Answering this question helps to understand why new language constructs usually propagate along an S-shaped curve with a rather sudden transition towards global agreement. It also helps to analyze and design new technologies that support or orchestrate self-organizing communication systems, such as recent social tagging systems for the web. The article introduces and studies a microscopic model of communicating autonomous agents performing language games without any central control. We show that the system undergoes a disorder/order transition, going trough a sharp symmetry breaking process to reach a shared set of conventions. Before the transition, the system builds up non-trivial scale-invariant correlations, for instance in the distribution of competing synonyms, which display a Zipf-like law. These correlations make the system ready for the transition towards shared conventions, which, observed on the time-scale of collective behaviors, becomes sharper and sharper with system size. This surprising result not only explains why human language can scale up to very large populations but also suggests ways to optimize artificial semiotic dynamics.

The Structure of Collaborative Tagging Systems

Scott Golder — 2005-08-27T17:06:09-00:00

(18 Aug 2005)

Collaborative tagging describes the process by which many users add metadata in the form of keywords to shared content. Recently, collaborative tagging has grown in popularity on the web, on sites that allow users to tag bookmarks, photographs and other content. In this paper we analyze the structure of collaborative tagging systems as well as their dynamical aspects. Specifically, we discovered regularities in user activity, tag frequencies, kinds of tags used, bursts of popularity in bookmarking and a remarkable stability in the relative proportions of tags within a given url. We also present a dynamical model of collaborative tagging that predicts these stable patterns and relates them to imitation and shared knowledge.

Open Source Democracy: How Online Communication is Changing Offline Politics

Douglas Rushkoff — 2005-11-08T23:54:28-00:00

(09 October 2003)

The Virtual Community: Homesteading on the Electronic Frontier, revised edition

Howard Rheingold — 2005-06-15T20:06:35-00:00

(01 November 2000)

Written by the man known as the First Citizen of the Internet, this book covers Rheingold's experiences with virtual communities. It starts off with his home community, The Well, out of Sausilito, CA, and makes its way through MUDs and beyond. No one understands the compelling strength of online community like Rheingold. Howard Rheingold has been called the First Citizen of the Internet. In this book he tours the "virtual community" of online networking. He describes a community that is as real and as much a mixed bag as any physical community -- one where people talk, argue, seek information, organize politically, fall in love, and dupe others. At the same time that he tells moving stories about people who have received online emotional support during devastating illnesses, he acknowledges a darker side to people's behavior in cyberspace. Indeed, contends Rheingold, people relate to each other online much the same as they do in physical communities. Originally published in 1993, The Virtual Community is more timely than ever. This edition contains a new chapter, in which the author revisits his ideas about online social communication now that so much more of the world's population is wired. It also contains an extended bibliography.

A Social Network for Societal-Scale Decision-Making Systems

Marko Rodriguez — 2005-06-29T16:48:02-00:00

(11 Dec 2004)

In societal-scale decision-making systems the collective is faced with the problem of ensuring that the derived group decision is in accord with the collective's intention. In modern systems, political institutions have instatiated representative forms of decision-making to ensure that every individual in the society has a participatory voice in the decision-making behavior of the whole--even if only indirectly through representation. An agent-based simulation demonstrates that in modern representative systems, as the ratio of representatives increases, there exists an exponential decrease in the ability for the group to behave in accord with the desires of the whole. To remedy this issue, this paper provides a novel representative power structure for decision-making that utilizes a social network and power distribution algorithm to maintain the collective's perspective over varying degrees of participation and/or ratios of representation. This work shows promise for the future development of policy-making systems that are supported by the computer and network infrastructure of our society.

Coordinating Expertise Among Emergent Groups Responding to Disasters

Ann Majchrzak — 2008-01-15T09:06:41-00:00

Organization Science, Vol. 18, No. 1. (January 2007), pp. 147-161.

Imagery, Creativity, and Emergent Structure

Finke — 2006-08-02T12:48:43-00:00

(1996), pp. 381-393.

Recent advances in the field of creative cognition have helped to reveal the cognitive structures and processes that are involved in creative thinking and imagination. This article begins by reviewing recent studies of creative imagery that have explored the emergent properties of mental images. The geneplore model of creative cognition, which describes how preinventive structures such as creative mental images are generated and interpreted, is then discussed. In discussing this model and its implications, a distinction is made between aspects of creative imagery that reflect conscious, deliberate control and those that reflect the absence of such control, as illustrated particularly by the emergence of unanticipated structures in imagined forms. The intentional, structured qualities of creative thinking are then contrasted with its spontaneous, unstructured qualities. The article concludes by discussing the recent topics of chaotic cognition and creative realism and how they bear on the general issue of balancing structured and unstructured processes in creative endeavors.

High-level perception, representation, and analogy: a critique of artificial-intelligence methodology

David Chalmers — 2006-07-25T10:09:27-00:00

(1995), pp. 169-193.

Complex Adaptive Systems + Soft Computing = Emergent Design Systems

MS Voss — 2006-12-01T12:32:39-00:00

(2000)

The focus of this paper is to illustrate how soft computing can be incorporated into the complex adaptive systems (CAS) framework to form a methodology for emergent design systems (EDS). Several design metaphors will be used to illustrate the application of the EDS methodology with respect to engineering design. Performance based structural design and architectural design will be used to elucidate the EDS approach. Fission fusion reactor design will be used as a conceptual framework to...

Modeling Creativity and Knowledge-Based Creative Design

John Gero — 2006-11-20T11:21:23-00:00

(1993)

Emergent semantics

S Staab — 2005-01-31T17:56:25-00:00

Intelligent Systems, IEEE [see also IEEE Expert], Vol. 17, No. 1. (2002), pp. 78-86.

The article discusses ways to let semantics emerge from simple observations from the bottom-up, rather than imposing concepts on the observations top-down, to provide precise query, retrieval, communication or translation for a wide variety of applications. The following areas are examined: image retrieval and databases; media information spaces including the Semantic Web and MPEG frameworks; language games for emergent semantics; and emergent semantics for ontologies

Principles of emergent design in online games: Mermaids phase 1 prototype

Celia Pearce — 2008-07-17T19:44:43-00:00

(2007), pp. 65-71.

High end complexity

Kirsty Kitto — 2008-01-13T05:53:38-00:00

International Journal of General Systems, Vol. 99999, No. 1. (2008), pp. 1-1.

Despite the general recognition of complexity as an important concept and decades of work, very little progress has been made in the attempt to define complexity. It is suggested that this is due to the fact that the definition of complex behaviour is itself complex, forming a scale from the simple to the more and more complex. Those systems at the high end of the scale are not at present well modelled, and reasons why this might be the case are presented. The possibility that quantum theories may be able to model such high end complexity is investigated.

Emergent Semantics Systems

Karl Tiziana — 2005-08-23T16:48:46-00:00

With new standards like RDF or OWL paving the way for the much anticipated Semantic Web, a new breed of very large scale semantic systems is about to appear. Traditional semantic reconciliation techniques, dependent upon shared vocabularies or global ontologies, cannot be used in such open and dynamic environments. Instead, new heuristics based on emerging properties and local consensuses have to be exploited in order to foster semantic interoperability in the large. In this paper, we...

Physical Properties Determining Self-Organization of Motors and Microtubules

Thomas Surrey — 2006-01-17T11:41:22-00:00

Science, Vol. 292, No. 5519. (11 May 2001), pp. 1167-1171.

The Wisdom of Crowds: Why the Many Are Smarter Than the Few and How Collective Wisdom Shapes Business, Economies, Societies and Nations

James Surowiecki — 2005-04-12T02:21:51-00:00

(25 May 2004)

The Hidden Power of Social Networks: Understanding How Work Really Gets Done in Organizations

Robert Cross — 2005-12-06T06:01:23-00:00

(02 June 2004)

Identifying and Leveraging the Hidden Social Networks That Drive Corporate Performance In today's flatter organizations, collaboration in employee networks has become critical to innovation and to both individual and companywide performance. Executives spend millions on new organizational designs, cultural initiatives, and technologies to promote the sharing of knowledge and expertise across functional, hierarchical, and divisional lines. Yet these efforts have achieved disappointing results. Rob Cross and Andrew Parker argue that's because most managers have little understanding of how their employees actually interact to get work done. In fact, formal "org charts" fail to reveal the often hidden social networks that truly drive--or hinder--an organization's performance. In this eye-opening book, Cross and Parker show managers how to find, assess, and support the networks most crucial to competitive success. Based on their in-depth study of more than sixty informal networks within organizations around the world, Cross and Parker show how managers can implement a wide range of specific and inexpensive actions-from bridging strategically important disconnects in a network to eliminating information "bottlenecks" to recognizing key connectors-that will enhance the powerful impact networks can have on performance and innovation.

Self-assembling hypertexts, weblogs, and wikis

Stuart Moulthrop — 2005-01-13T06:50:34-00:00

(2002), pp. 149-149.

Viewpoints on Emergent Semantics

Philippe Cudré-Mauroux — 2007-08-15T14:22:06-00:00

Journal on Data Semantics VI (2006), pp. 1-27.

We introduce a novel view on how to deal with the problems of semantic interoperability in distributed systems. This view is based on the concept of emergent semantics, which sees both the representation of semantics and the discovery of the proper interpretation of symbols as the result of a self-organizing process performed by distributed agents exchanging symbols and having utilities dependent on the proper interpretation of the symbols. This is a complex systems perspective on the problem of dealing with semantics. We highlight some of the distinctive features of our vision and point out preliminary examples of its application.

The Chatty Web: Emergent Semantics Through Gossiping

Karl Aberer — 2005-04-28T08:43:20-00:00

(2003)

This paper describes a novel approach for obtaining semantic interoperability among data sources in a bottom-up, semi-automatic manner without relying on pre-existing, global semantic models. We assume that large amounts of data exist that have been organized and annotated according to local schemas. Seeing semantics as a form of agreement, our approach enables the participating data sources to incrementally develop global agreement in an evolutionary and completely decentralized process that...

Ontologies Are Us: A Unified Model of Social Networks and Semantics

Peter Mika — 2007-02-26T16:47:51-00:00

: The Semantic Web â ISWC 2005 (2005), pp. 522-536.

Gravity as an emergent phenomenon: A conceptual description

T Padmanabhan — 2007-06-14T15:58:15-00:00

(12 Jun 2007)

I describe several broad features of a programme to understand gravity as an emergent, long wavelength, phenomenon (like elasticity) and discuss one concrete framework for realizing this paradigm in the backdrop of several recent results.

Evaluating emergent collaboration on the Web

Loren Terveen — 2005-04-28T16:48:52-00:00

(1998), pp. 355-362.

Towards performance guarantees for emergent behavior

DM Lyons — 2005-09-19T10:23:52-00:00

Robotics and Automation, 2004. Proceedings. ICRA '04. 2004 IEEE International Conference on, Vol. 4 (2004), pp. 4153-4158 Vol.4.

It is important to be able to guarantee the safety and effectiveness of robot behavior in applications where robots must operate alongside people or in hazardous situations. A modeling framework based on port automata and asynchronous communication is introduced in this paper. By looking at the internal transitions between port communications, an analysis approach is developed that removes the combinatoric issues of looking at an asynchronous combination of robot and environment. An example application of the approach to wheel slippage in a mobile robot is presented.

Quantum Graphity: a model of emergent locality

Tomasz Konopka — 2008-05-13T14:59:10-00:00

(6 Jan 2008)

Quantum graphity is a background independent model for emergent locality, spatial geometry and matter. The states of the system correspond to dynamical graphs on N vertices. At high energy, the graph describing the system is highly connected and the physics is invariant under the full symmetric group acting on the vertices. We present evidence that the model also has a low-energy phase in which the graph describing the system breaks permutation symmetry and appears to be ordered, low-dimensional and local. Consideration of the free energy associated with the dominant terms in the dynamics shows that this low-energy state is thermodynamically stable under local perturbations. The model can also give rise to an emergent U(1) gauge theory in the ground state by the string-net condensation mechanism of Levin and Wen. We also reformulate the model in graph-theoretic terms and compare its dynamics to some common graph processes.

The Hidden Order of Wikipedia

Fernanda Viégas — 2007-10-30T15:59:24-00:00

Online Communities and Social Computing (2007), pp. 445-454.

We examine the procedural side of Wikipedia, the well-known internet encyclopedia. Despite the lack of structure in the underlying wiki technology, users abide by hundreds of rules and follow well-defined processes. Our case study is the Featured Article (FA) process, one of the best established procedures on the site. We analyze the FA process through the theoretical framework of commons governance, and demonstrate how this process blends elements of traditional workflow with peer production. We conclude that rather than encouraging anarchy, many aspects of wiki technology lend themselves to the collective creation of formalized process and policy.

Structure of Self-Organized Blogosphere

Feng Fu — 2006-09-01T15:10:19-00:00

(15 Jul 2006)

In this paper, the statistical analysis of one blog community is presented. The quantities such as degree distribution, clustering coefficient, average shortest path length are calculated to capture the features of the blogging network. We demonstrate that the blogging network has small-world property and the in and out degree distributions have power-law forms. The analysis also confirms that blogging networks show in general disassortative mixing pattern. Furthermore, the fraction of the number of page views of blogs follows a power law.

Structured development of problem solving methods

D Fensel — 2007-11-30T12:03:36-00:00

Transactions on Knowledge and Data Engineering, Vol. 13, No. 6. (2001), pp. 913-932.

Problem solving methods (PSMs) describe the reasoning components of knowledge-based systems as patterns of behavior that can be reused across applications. While the availability of extensive problem solving method libraries and the emerging consensus on problem solving method specification languages indicate the maturity of the field, a number of important research issues are still open. In particular, very little progress has been achieved on foundational and methodological issues. Hence, despite the number of libraries which have been developed, it is still not clear what organization principles should be adopted to construct truly comprehensive libraries, covering large numbers of applications and encompassing both task-specific and task-independent problem solving methods. In this paper, we address these "fundamental" issues and present a comprehensive and detailed framework for characterizing problem solving methods and their development process. In particular, we suggest that PSM development consists of introducing assumptions and commitments along a three-dimensional space defined in terms of problem-solving strategy, task commitments, and domain (knowledge) assumptions. Individual moves through this space can be formally described by means of adapters. In the paper, we illustrate our approach and argue that our architecture provides answers to three fundamental problems related to research in problem solving methods: 1) what is the epistemological structure and what are the modeling primitives of PSMs? 2) how can we model the PSM development process? and 3) how can we develop and organize truly comprehensive and manageable libraries of problem solving methods?

Elephants Don't Play Chess

Rodney Brooks — 2005-07-06T22:23:25-00:00

Robotics and Autonomous Systems, Vol. 6, No. 1&2. (June 1990), pp. 3-15.

this paper we argue that the symbol system hypothesis upon which classical AI is base is fundamentally flawed, and as such imposes severe limitations on the fitness of its progeny. Further, we argue that the dogma of the symbol system hypothesis implicitly includes a number of largely unfounded great leaps of faith when called upon to provide a plausible path to the digital equivalent of human level intelligence. It is the chasms to be crossed by these leaps which now impede classical AI...

Recommending Emergent Teams

Shawn Minto — 2007-09-20T22:44:33-00:00

Mining Software Repositories, 2007. ICSE Workshops MSR '07. Fourth International Workshop on (2007), pp. 5-5.

To build successful complex software systems, developers must collaborate with each other to solve issues. To facilitate this collaboration, specialized tools, such as chat and screen sharing, are being integrated into development environments. Currently, these tools require a developer to maintain a list of other developers with whom they may wish to communicate and to determine who within this list has expertise for a specific situation. For large, dynamic projects, like several successful open-source projects, these requirements place an unreasonable burden on the developer. In this paper, we show how the structure of a team emerges from how developers change software artifacts. We introduce the Emergent Expertise Locator (EEL) that uses emergent team information to propose experts to a developer within their development environment as the developer works. We found that EEL produces, on average, results with higher precision and higher recall than an existing heuristic for expertise recommendation.

Communities of Practice: Performance and Evolution

Bernardo Huberman — 2007-04-24T00:31:03-00:00

Computational and Mathematical Organization Theory, Vol. 1 (1995), pp. 73-92.

We present a detailed model of collaboration in communities of practice and we examine its dynamical consequences for the group as a whole. We establish the existence of a novel mechanism that allows the community to naturally adapt to growth, specialization, or changes in the environment without the need for central controls. This mechanism relies on the appearance of a dynamical instability that initates an exploration of novel interactions, eventually leading to higher performance for the...

ONTOCOPI: Methods and Tools for Identifying Communities of Practice

H Alani — 2007-04-24T00:26:52-00:00

(2002)

The paper describes ONTOCOPI, a tool for identifying communities of practice (COPs) by analysing ontologies of the relevant working domain. COP identification is currently a resource-heavy process largely based on interviews. ONTOCOPI attempts to uncover informal COP relations by spotting patterns in the formal relations represented in ontologies, traversing the ontology from instance to instance via selected relations. Experiments to determine particular COPs from an academic ontology are...

Love: an emergent property of the mammalian autonomic nervous system.

SW Porges — 2005-10-13T04:34:17-00:00

Psychoneuroendocrinology, Vol. 23, No. 8. (November 1998), pp. 837-861.

The evolution of the autonomic nervous system provides an organizing principle to interpret the adaptive significance of mammalian affective processes including courting, sexual arousal, copulation, and the establishment of enduring social bonds. According to the Polyvagal Theory (Porges, 1995, 1996, 1997), the well-documented phylogenetic shift in the neural regulation of the autonomic nervous system passes through three stages, each with an associated behavioral strategy. The first stage is characterized by a primitive unmyelinated visceral vagus that fosters digestion and responds to threat by depressing metabolic activity. Behaviorally, the first stage is associated with immobilization behaviors. The second stage is characterized by the sympathetic nervous system that is capable of increasing metabolic output and inhibiting the visceral vagus to foster mobilization behaviors necessary for 'fight or flight'. The third stage, unique to mammals, is characterized by a myelinated vagus that can rapidly regulate cardiac output to foster engagement and disengagement with the environment. The mammalian vagus is neuroanatomically linked to the cranial nerves that regulate social engagement via facial expression and vocalization. The Polyvagal Theory provides neurobiological explanations for two dimensions of intimacy: courting and the establishment of enduring pair-bonds. Courting is dependent upon the social engagement strategies associated with the mammalian vagus. The establishment of enduring pair-bonds is dependent upon a co-opting of the visceral vagus from an immobilization system associated with fear and avoidance to an immobilization system associated with safety and trust. The theory proposes that the phylogenetic development of the mammalian vagus is paralleled by a specialized communication, via oxytocin and vasopressin, between the hypothalamus and the medullary source nuclei of the viscera vagus, which facilitates sexual arousal, copulation, and the development of enduring pair-bonds.

Massive particles in acoustic space-times emergent inertia and passive gravity

Mordehai Milgrom — 2006-02-01T16:43:39-00:00

(29 Jan 2006)

I show that massive-particle dynamics can be simulated by a weak, spherical, external perturbation on a potential flow in an ideal fluid. The effective Lagrangian is of the form mc^2L(U^2/c^2), where U is the velocity of the particle relative to the fluid and c the speed of sound. This can serve as a model for emergent relativistic inertia a la Mach's principle with m playing the role of inertial mass, and also of analog gravity where it is also the passive gravitational mass. m depends on the particle type and intrinsic structure, while L is universal: For D dimensional particles L is proportional to the hypergeometric function F(1,1/2;D/2;U^2/c^2). Particles fall in the same way in the analog gravitational field independent of their internal structure, thus satisfying the weak equivalence principle. For D less or equal 5 they all have a relativistic limit with the acquired energy and momentum diverging as U approaches c. For D less or equal 7 the null geodesics of the standard acoustic metric solve our equation of motion. Interestingly, for D=4 the dynamics is very nearly Lorentzian. The particles can be said to follow the geodesics of a generalized acoustic metric of a Finslerian type that shares the null geodesics with the standard acoustic metric. In vortex geometries, the ergosphere is automatically the static limit. As in the real world, in “black hole” geometries circular orbits do not exist below a certain radius that occurs outside the horizon. There is a natural definition of antiparticles; and I describe a mock particle vacuum in whose context one can discuss, e.g., particle Hawking radiation near event horizons.

Formative Versus Reflective Indicators in Organizational Measure Development: A Comparison and Empirical Illustration

Diamantopoulos — 2006-12-08T21:05:45-00:00

British Journal of Management, Vol. 17, No. 4. (December 2006), pp. 263-282.

A comparison is undertaken between scale development and index construction procedures to trace the implications of adopting a reflective versus formative perspective when creating multi-item measures for organizational research. Focusing on export coordination as an illustrative construct of interest, the results show that the choice of measurement perspective impacts on the content, parsimony and criterion validity of the derived coordination measures. Implications for practising researchers seeking to develop multi-item measures of organizational constructs are considered.

Is Formative Measurement Really Measurement? Reply to Bollen (2007) and Bagozzi (2007)

Roy Howell — 2007-08-26T13:35:47-00:00

Psychological Methods, Vol. 12, No. 2. (June 2007), pp. 238-245.

R. D. Howell, E. Breivik, and J. B. Wilcox (2007) examined the use of formative measurement models in theory testing in the social sciences. K. A. Bollen (2007) and R. P. Bagozzi (2007) have provided comments on this work. In this article, the authors reply to the commentators and suggest that the conclusions reached in the original article and the basis for those conclusions remain sound. They address the issue of misspecification raised by Bollen (2007) and the alternative to their realist philosophy of measurement offered by Bagozzi (2007). They conclude that misspecification as construed by Bollen (2007) will typically be undetectable in practice and cannot be distinguished from interpretational confounding. This can result in substantively different constructs retaining the same name from study to study, hindering the accumulation of knowledge. They further conclude that traditional reflective measurement is a better option for researchers in theory testing.

On the Meaning of Formative Measurement and How It Differs From Reflective Measurement: Comment on Howell, Breivik, and Wilcox (2007)

Richard Bagozzi — 2007-08-26T13:35:23-00:00

Psychological Methods, Vol. 12, No. 2. (June 2007), pp. 229-237.

R. D. Howell, E. Breivik, and J. B. Wilcox (2007) have presented an important and interesting analysis of formative measurement and have recommended that researchers abandon such an approach in favor of reflective measurement. The author agrees with their recommendations but disagrees with some of the bases for their conclusions. He suggests that although latent variables refer to mental states or mental events that have objective reality, to gain knowledge of the existence of these states or events requires that emphasis be placed on the nature and interpretation of the relationship between latent and manifest variables. This relationship is not a causal one but rather a kind of correspondence rule that contains theoretical, empirical, operational, and logical meanings as part of its content and structure. Implications of the above views are discussed for formative and reflective measurement.

Interpretational Confounding Is Due to Misspecification, Not to Type of Indicator: Comment on Howell, Breivik, and Wilcox (2007)

Kenneth Bollen — 2007-08-26T13:34:39-00:00

Psychological Methods, Vol. 12, No. 2. (June 2007), pp. 219-228.

R. D. Howell, E. Breivik, and J. B. Wilcox (2007) have argued that causal (formative) indicators are inherently subject to interpretational confounding. That is, they have argued that using causal (formative) indicators leads the empirical meaning of a latent variable to be other than that assigned to it by a researcher. Their critique of causal (formative) indicators rests on several claims: (a) A latent variable exists apart from the model when there are effect (reflective) indicators but not when there are causal (formative) indicators, (b) causal (formative) indicators need not have the same consequences, (c) causal (formative) indicators are inherently subject to interpretational confounding, and (d) a researcher cannot detect interpretational confounding when using causal (formative) indicators. This article shows that each claim is false. Rather, interpretational confounding is more a problem of structural misspecification of a model combined with an underidentified model that leaves these misspecifications undetected. Interpretational confounding does not occur if the model is correctly specified whether a researcher has causal (formative) or effect (reflective) indicators. It is the validity of a model not the type of indicator that determines the potential for interpretational confounding.

Reconsidering Formative Measurement

Roy Howell — 2007-08-26T13:34:15-00:00

Psychological Methods, Vol. 12, No. 2. (June 2007), pp. 205-218.

The relationship between observable responses and the latent constructs they are purported to measure has received considerable attention recently, with particular focus on what has become known as formative measurement. This alternative to reflective measurement in the area of theory-testing research is examined in the context of the potential for interpretational confounding and a construct's ability to function as a point variable within a larger model. Although these issues have been addressed in the traditional reflective measurement context, the authors suggest that they are particularly relevant in evaluating formative measurement models. On the basis of this analysis, the authors conclude that formative measurement is not an equally attractive alternative to reflective measurement and that whenever possible, in developing new measures or choosing among alternative existing measures, researchers should opt for reflective measurement. In addition, the authors provide guidelines for researchers dealing with existing formative measures.

Multidimensional constructs in structural equation analysis: An illustration using the job perception and job satisfaction constructs

CS Wong — 2007-12-02T12:13:50-00:00

J. Manage., Vol. 25, No. 2. (1999), pp. 143-160.

This article contrasts the composite view of the relationship between multidimensional constructs and their facets/dimensions with the factor view. The composite view assumes that facets are components of the composite constructs, while the factor view assumes that facets are manifestations of latent constructs. An empirical study is used to illustrate the fact that these two views will lead to different conclusions about the relationship of constructs in covariance structure analyses. It is suggested that researchers must examine the theoretical basis of their topic in order to determine whether the factor or composite view is more suitable for the multidimensional construct of interest.

Export performance measurement: Reflective versus formative indicators

A Diamantopoulos — 2007-12-02T12:11:16-00:00

Int. Mark. Rev., Vol. 16, No. 6. (1999), pp. 444-457.

While the conceptualization and operationalization of export performance has been receiving increased attention in the literature, practically all multi-item measures of export performance available are based on reflective (effect) indicators. Explores an alternative measurement approach based on formative (causal) indicators and examines the implications of constructing an index rather than a scale of export performance. The aim is to assist researchers in choosing the appropriate measurement model for their needs when conducting substantive export performance studies.

Problems in the Measurement of Latent Variables in Structural Equations Causal Models

Patricia Cohen — 2007-12-09T14:12:22-00:00

Applied Psychological Measurement, Vol. 14, No. 2. (1 June 1990), pp. 183-196.

Some problems in the measurement of latent variables in structural equations causal models are presented, with examples from recent empirical studies. Latent variables that are theoretically the source of correlation among the empirical indica tors are differentiated from unmeasured variables that are related to the empirical indicators for other reasons. It is pointed out that these should also be represented by different analytical models, and that much published research has treated this distinction as if it had no analytic consequences. The connection between this theoretical distinction and disattenuation effects in latent variable models is shown, and problems with these estimates are discussed. Finally, recommendations are made for decisions about whether and how to measure latent variables when manifest variables are potentially available. 10.1177/014662169001400207

Conventional Wisdom on Measurement: A Structural Equation Perspective

Kenneth Bollen — 2007-08-26T10:46:02-00:00

Psychological Bulletin, Vol. 110, No. 2. (September 1991), pp. 305-314.

The applicability of 5 conventional guidelines for construct measurement is critically examined: (a) Construct indicators should be internally consistent for valid measures, (b) there are optimal magnitudes of correlations between items, (c) the validity of measures depends on the adequacy with which a specified domain is sampled, (d) within-construct correlations must be greater than between-construct correlations, and (e) linear composites of indicators can replace latent variables. A structural equation perspective is used, showing that without an explicit measurement model relating indicators to latent variables and measurement errors, none of these conventional beliefs hold without qualifications. Moreover, a "causal" indicator model is presented that sometimes better corresponds to the relation of indicators to a construct than does the classical test theory "effect" indicator model.

Index construction with formative indicators: An alternative to scale development

A Diamantopoulos — 2007-12-02T11:29:19-00:00

Journal of Market Research, Vol. 38, No. 2. (2001), pp. 269-277.

Although the methodological literature is replete with advice regarding the development and validation of multi-item scales based on reflective measures, the issue of index construction using formative measures has received little attention. The authors seek to address this gap by (1) examining the nature of formative indicators, (2) discussing ways in which the quality of formative measures can be assessed, and (3) illustrating the proposed procedures with empirical data. The aim is to enhance researchers' understanding of formative measures and assist them in their index construction efforts.

The use of causal indicators in covariance structure models: some practical issues.

RC Maccallum — 2007-11-19T15:41:11-00:00

Psychological Bulletin, Vol. 114, No. 3. (November 1993), pp. 533-541.

In conventional representations of covariance structure models, indicators are defined as linear functions of latent variables, plus error. In an alternative representation, constructs can be defined as linear functions of their indicators, called causal indicators, plus an error term. Such constructs are not latent variables but composite variables, and they have no indicators in the conventional sense. The presence of composite variables in a model can, in some situations, result in problems with identification of model parameters. Also, the use of causal indicators can produce models that imply zero correlation among many measured variables, a problem resolved only by the inclusion of a potentially large number of additional parameters. These phenomena are demonstrated with an example, and general principles underlying them are discussed. Remedies are described so as to allow for the evaluation of models that contain causal indicators.

Evolution of homing navigation in a real mobile robot

D Floreano — 2007-02-08T14:32:58-00:00

In this paper we describe the evolution of a discrete-time recurrent neural network to control a real mobile robot. In all our experiments the evolutionary procedure is carried out entirely on the physical robot without human intervention. We show that the autonomous development of a set of behaviors for locating a battery charger and periodically returning to it can be achieved by lifting constraints in the design of the robot/environment interactions that were employed in a preliminary...

Performance evaluation of a multi-robot search & retrieval system: Experiences with MinDART

P Rybski — 2007-02-08T14:30:57-00:00

(2003)

The costs of developing mobile robot teams can be reduced if they are designed to exploit swarm techniques. In this methodology many simple homogeneous units solve complex tasks through emergent behavior. The challenge lies in selecting an appropriate control strategy for the individual units. Complexity in design costs both money and time, therefore a control strategy should be just complex enough to perform the task successfully in a variety of environments, relative to some performance...

Emergent biogeography of microbial communities in a model ocean.

MJ Follows — 2007-04-02T11:00:39-00:00

Science, Vol. 315, No. 5820. (30 March 2007), pp. 1843-1846.

A marine ecosystem model seeded with many phytoplankton types, whose physiological traits were randomly assigned from ranges defined by field and laboratory data, generated an emergent community structure and biogeography consistent with observed global phytoplankton distributions. The modeled organisms included types analogous to the marine cyanobacterium Prochlorococcus. Their emergent global distributions and physiological properties simultaneously correspond to observations. This flexible representation of community structure can be used to explore relations between ecosystems, biogeochemical cycles, and climate change.

tagging, communities, vocabulary, evolution

Shilad Sen — 2006-11-28T14:55:38-00:00

(2006), pp. 181-190.

Exploring social annotations for the semantic web

Xian Wu — 2006-08-14T21:57:10-00:00

(2006), pp. 417-426.