Popular Concepts beyond Organizations: Exploring New Dimensions of Information Technology Innovations The abundance of innovation concepts in the world of information technology and their differentiated influence on the design, production, and use of IT in organizations make it important that we understand what shapes these concepts themselves. Taking the perspective that an IT innovation concept emerges and evolves beyond organizational boundaries in a community, I argue that the prevalence or popularity of the concept in IT discourse positively influences the adoption of the underlying innovation. Then with the aim to explore what makes an IT innovation concept popular, my empirical analysis of the once highly popular concept ERP (enterprise resource planning) suggests that (1) the popularity of ERP was influenced positively by the prevalence of highlighted business problems that ERP was claimed to solve; (2) ERP's popularity was influenced negatively by the prevalence of related innovation concepts; and (3) these influences largely disappeared after ERP passed its peak popularity. These results imply that the popularity of an IT innovation concept responds to the broader climate of business and relies on the right type of attention drawn and released by other concepts in a network of concepts. Going beyond the dominant paradigm, this paper helps broaden IT innovation research along two new dimensions: toward the innovation concept, as a complement to material innovation, and toward community-level analysis, as an extension of the traditional organizational analysis. The paper also suggests that practitioners evaluate an innovation concept's fit with the broader environment and relationship with other popular concepts, as a way to make sense of the innovation and anticipate its impact on IT practice. Reflecting on the decline of business process reengineering (BPR), an information technologyenabled concept that he introduced along with Michael Hammer and James Champy in the early 1990s, Thomas Davenport recently lamented the faddishness of the IT world. His expression "to stick" in the quote above means to become highly visible, prevalent, or popular in the on-going discourse about IT. Although numerous concepts like BPR exist, few of them stick. When an IT concept sticks, it often brings about profound innovations in IT practice. Consider knowledge management (KM), which Davenport popularized with Laurence Prusak a few years after BPR was introduced. The KM concept emerged to become a highly popular topic across the trade and popular press and the subject of much academic research. KM has been translated into an $8.8 billion worldwide market for software vendors and consultants (Malhotra, 2005) and one of the most important corporate performance-enhancement initiatives.. 2 When an innovation concept fails to stick, i.e., when it fails to attain a certain level of popularity in IT discourse, the failure tends to forestall the development and diffusion of related material innovations.. Despite so much at stake, the dominant paradigm for IT innovation research is primarily focused on the adoption of new IT in the material, rather than conceptual, form. An IT innovation in the conceptual form can be referred to as an IT innovation concept, which I define as a collective idea for the development and utilization of an IT innovation. Either BPR or knowledge management, for example, represents a concept that broadly addresses what the innovation is, why organizations should undertake the innovation, and how to do so. In contrast, an IT innovation in its material form corresponds to the physical aspects such as hardware, software, and the processes enabled. Thus far, there has been little sustained research to understand who creates IT innovation concepts, how they are developed, why some concepts become highly popular but others don't, and what different concepts may entail for the adoption, implementation, and use of IT innovations.. To account for the cause and effect of an innovation concept, we should examine the collective that generates and develops it. Each collective is a community of diverse organizations interested in an innovation; members of the community talk and write about the innovation. I theorize that concepts more prevalent or popular in this on-going conversation are more likely to prompt the adoption of underlying innovations. Then the crucial question is: What makes an IT innovation concept popular?. As an initial step to answer this question, I conducted an empirical study to examine the popularity of ERP (enterprise resource planning), arguably the most popular IT innovation concept in the past few decades. I hypothesize that the popularity of ERP was determined by the prevalence of the problems that ERP was purported to solve and by the popularity of innovation concepts related to ERP. The findings suggest that, first, the popularity of ERP, as measured by quarterly count of articles about ERP in publication outlets, was influenced positively by the prevalence of highlighted business problems that ERP was claimed to solve, but not by the problem ERP had originally been conceived to solve. Second, ERP's popularity was influenced negatively by the prevalence of innovation concepts closely related to ERP, but not by concepts distantly related or unrelated to ERP. Third, the influence of problem discourse and related older concepts disappeared after ERP passed its peak popularity, but the influence of related newer concepts remained. These results imply that the popularity of an IT innovation concept responds to the broader climate of business and relies on the Informational cascade theory, further, suggests that, when their private assessments of an innovation go against the weight of observed adoptions by others, prospective adopters may discount their own assessments and follow others to adopt the innovation (Bikhchandani et al., 1992; Walden and Browne, 2002) . This "herd behavior" may be optimal because, according to the theory of rational expectations, the crowd's average expected value of the innovation may approach the true value (Au and Kauffman, 2003) . Common across these economic-rationalistic studies is the primary emphasis on other organizations that are also adopters of the innovations.. Social perspectives, on the other hand, are primarily concerned with the factors and processes in the social environment of the focal innovating organization. Studies from the socio-relational perspective have examined the implications of interorganizational relationships on innovations. For example, research on social contagion has shown that adoptions are more likely to be imitated when the adopters, often in a network of competitors, are perceived as more successful, prominent, and similar to the focal organization (Greve, 1995; Strang and Macy, 2001) . Exploring a broader set of "other organizations," research on interorganizational IT has shown that adoption decisions are closely linked among organizations in the same value chain and that, in particular, power and trust among trading partners are important reasons for and consequences of innovations (Hart and Saunders, 1997; . Moreover, taking an even broader view of social relations, innovation scholars have argued for "industrial infrastructures" for the innovations -networks of support and sponsorship by "other organizations" such as government agencies, research institutions, industry and professional associations (King et al., 1994; Lynn et al., 1996) . For example, even though the Internet technology was invented in the 1960s, it had not been widely applied until the early 1990s when the United States government approved its use for commercial purposes (David, 2001) .. While the competitive, transactional, collaborative, and regulative relationships provide important social structures for innovations, cognitive bases are also essential. That is, organizations must understand the innovations they adopt and use. The socio-cognitive perspective of innovation research views other organizations as important sources for that understanding. For example, government authorities, as part of the industrial infrastructure just mentioned, may go beyond their regulative roles to influence the belief systems of the adopter organizations through persuasion and propaganda (King et al., 1994) . Organizing vision theory suggests that various organizations interested in an IT innovation form a community where they create and develop a vision, "for organizing in a way that embeds and utilizes information technology in organizational structures and processes" (Swanson and Ramiller, 1997, p. 460) . Management fashion theory highlights the roles of "management knowledge entrepreneurs" -consulting, media, and research organizations that create and disseminate management knowledge -in shaping the wave-like collective attention paid to innovations (Abrahamson, 1996a; Abrahamson and Fairchild, 1999) . Similarly, research from the social construction of technology and social informatics traditions has studied the organizations that frame the innovations in their design and use (Bijker, 1987; Iacono and Kling, 2001 ).. Taking all of this into account, I suggest that IT innovation research extend its focus from organizational analysis to other organizations. The economic-rationalistic view of the other organizations essentially stays within the dominant paradigm (Fichman, 2004) . Empirical research from the socio-relational perspective has been steadily increasing (Strang and Soule, 1998) . Much remains to be explored on how other organizations shape social cognition, which, in turn, shapes innovations (DeSanctis quoted in Swanson and Ramiller, 1997, p. 458) . Embedded implicitly or explicitly in the studies from the socio-cognitive perspective is the idea that an innovation not only takes place in adopter organizations where it is materialized, but also exists in a collective environment where adopters, vendors, consultants, investors, journalists, analysts, academics, and others are interested in developing the innovation as a concept. In this sense, a broader, community level of analysis of IT innovations is more than a simple shift in the level of abstraction. While the material aspect of an innovation is always associated with particular organizations, it is the innovation concept that travels across organizational boundaries (Newell et al., 2000) . The recent wave of mergers and acquisitions among enterprise software providers signifies a consolidating marketplace for material IT innovations. However, the marketplace for innovation concepts remains messy and inefficient (Pfeffer and Sutton, 2006) . Anyone with an idea can enter and exit the marketplace with minimal cost. At any time, numerous IT innovation concepts are competing for the already scarce attention of practitioners. What these concepts propose and promote is often inconsistent and ambiguous. Their influence on the design, production, and use of IT in organizations is often different, and it is difficult to predict the impact of any particular concept. Thus far, IT innovation research has little to offer when it comes to the causes and production of IT innovation concepts and their consequences on the adoption and diffusion of IT innovations.. This paper has centered on the IT innovation concept, as opposed to the conventional focus on material innovation. Taking the perspective that an IT innovation concept evolves beyond the boundaries of organizations in a community, I have argued that the increased prevalence of an IT innovation concept in discourse, or its popularity, may lead to an increased likelihood of innovation adoption. Realizing that popularity is an often-talked-about but poorly understood concept itself, I have focused my empirical investigation on one question: What makes a concept popular? The empirical case study of ERP has three findings. First, when an IT innovation is framed as the solution to certain business problems, the prevalence of the problems that discourse highlights and brings to managers' collective attention is positively associated with the popularity of the innovation; whereas the prevalence of the problems that discourse fails to highlight has no effect on the popularity of the innovation. Second, the popularity of concepts related to the focal innovation concept is negatively associated with the popularity of the new concept, because they rely on the same type of attention; whereas the popularity of concepts unrelated to a new concept has no effect on its popularity. Third, the effects of highlighted problem discourses and older related concepts on the popularity of a focal concept disappear after the concept passes its peak popularity, but the influence of newer related concepts remains.. Interpretation of the findings should remain tentative due to several limitations. First, ABI only includes published written discourse. Although many articles quote content from interviews and speeches, published discourse is only one type of discourse and may not be representative. Other types of discourse should also be examined using effective methods such as observation, interview, and survey in future research. Second, although the articles on the problems of information fragmentation and operational inefficiency were carefully selected following conventional qualitative analysis procedures, the selection process may still have left out some articles that discuss these two problems in ways not detected by this method. Therefore, research in the future may explore Wang/Information Technology Innovations methods with higher reliability. Third, regarding the relationships between related innovations, this study only examined an ad hoc list of concepts, and their relatedness was heuristically inferred from previous literature. Future research should develop a more systematic method to select innovation concepts, formally theorize and measure their relatedness, and test the moderating effect of concept relatedness on popularity. Fourth, the empirical study has focused on only two factors (problem discourse and related innovations). Despite the significance of these factors, other drivers for popularity may also exist. For example, as alluded to earlier, future research could explore the influence of high-profile organizations producing or adopting IT innovations. Last, with respect to generalizability, although this single-case empirical study allowed me to generalize from the findings toward a theory of popularity, which, in turn, can be generalized to a richer theory of IT innovation (Lee and Baskerville, 2003) , the findings themselves cannot be directly generalized to other innovation concepts. Therefore, an immediate direction for future research is toward validating the findings among other concepts, particularly associated with different levels of controversy, as highlighted by the discussion on Linux. Future research on multiple innovations should also examine the content of the discourse and assess how controversy and/or various sentiments shape the relationship between popularity and adoption.. Notwithstanding these limitations, this study responds earnestly to Fichman's call for IT innovation research to go beyond the dominant paradigm (Fichman, 2004) . Theoretically, the paper contributes to the understanding of IT innovations along two new dimensions. The primary dimension is the innovation concept, as a complement of material innovation processes. Only by making the distinction between concept and material can one study and understand their relationship. I have argued that innovation concepts traveling across organizational boundaries constitute the reality of today's IT world and shape the diffusion of innovations in material form. In particular, after introducing and theorizing popularity of an innovation concept as a potentially important driver of adoption, the paper has gone further to investigate some of the determinants of popularity. The empirical findings suggest that framing an innovation as the solution to a problem may not necessarily make the innovation concept popular. Rather, links to a widespread business problem that discourse highlights and brings to managers' collective attention may popularize the innovation, even as an unintended or partial solution. This conclusion is consistent with findings from studies of popular management innovations (e.g., Abrahamson and Fairchild, 1999) and echoes Davenport, who argued that innovation concepts "that get picked up by the marketplace are the ones that resonate with the zeitgeist" (Kleiner, 2000, p. 30, original emphasis) . Using Y2K and legacy systems as examples, the paper outlined a concrete way to discern and measure such resonance. Further, resonance with the zeitgeist might not guarantee imminent popularity if practitioners' attention has been exhausted by other related innovations. For that reason, had MRP II and BPR prolonged their popularity somehow, ERP would not have reached the popularity that it did in the 1990s. To varying degrees, innovation concepts are related in idea networks that have more dimensions and are more dynamic than any predefined problem domains or niches found in previous research on popular management innovations. The structure of these idea networks and their impact on innovation practice are just beginning to be understood. While this paper has made an initial contribution to that understanding, future research should explore the fascinating structure of attention flowing through the networks of innovation concepts (Davenport and Beck, 2001 ).. The other new dimension of IT innovation research is the community, comprising diverse actors interested in developing an innovation concept. As concepts rarely stay within the confines of any particular organization, the conventional organizational analysis is inadequate to explain the IT innovation phenomenon. An innovative user, the traditional focus of adoption research, did not introduce the ERP concept. An innovative vendor, the traditional focus of new product development and marketing research, did not introduce the ERP concept. Rather, ERP was introduced by the market research firm Gartner Group. This type of organization is often bundled with other players and factors in the background or context in conventional diffusion research. In launching the ERP concept, Gartner played a leading role. Yet, ERP gained popularity through joint development by vendors, users, consultants, and others in the community. Hence, community-level analysis of IT innovations is warranted (Wang and Ramiller, 2004) . This study has analyzed the community members' on-going conversation, or discourse, about ERP. The findings suggest that such communities of interest are dynamic in terms of membership and size. For example, some members of the MRP II community may have joined the ERP community, whose members might have later departed to join the CRM community. Future research should study the dynamic constitution of innovation communities, the differentiated influences of community members, and the process by which members launch innovation concepts and sustain their popularity through discourse.. Taken together, the new dimensions make up a new lens to look at the IT innovation phenomenon. This new lens has relaxed rigid or even unrealistic assumptions implicit in the dominant paradigm. For example, the new perspective does not assume that the adoption of innovation is an independent individual decision based entirely on bounded rationality. Rather, each adoption is informed by a grand concept produced by a larger community. Nevertheless, the new lens does not reject insights from the dominant paradigm. As Figure 5 shows, complementary views from both lenses constitute a binocular view, bringing us much closer to the reality of IT innovations.. Practically speaking, this study challenges both practitioners and researchers to pay attention to innovation concepts and their evolution on a larger stage. Today on that stage, ERP has lost its limelight to other popular concepts such as RFID (radio frequency identification). Before a vendor invests millions of dollars in a new product line for RFID, a company spends hundreds of thousands of dollars on adopting and implementing RFID, a consulting firm deploys an entire unit to consult on RFID, a researcher devotes a few of his/her most productive years to RFID research, and investors put billions in RFID stocks, they deserve to know why this 30-year-old technology 15 has become so popular today. Discourse analysis demonstrated here affords a useful tool for monitoring innovation concepts' popularity and for explaining that popularity. As Arrow 4 in Figure 5 suggests, discourses on the business problems and related concepts shape the focal concept's popularity. Those interested in RFID should be on the lookout for RFID's link to widespread problems "in the spirit" of our time and arguments regarding RFID's relationship with older innovations in the discourse. Based on their own evaluations of these claims and arguments, practitioners and researchers can then make informed decisions rather than jump on the RFID bandwagon mindlessly. Further, factors identified in this study such as problem discourse and related concepts can be used to forecast innovation concepts' popularity. In this sense, the paper joins the broader effort to predict which 15 RFID Journal frequently asked questions, available www.rfidjournal.com/faq/16/52, current January 20, 2006.. Numeric labels do not represent temporal sequencing. Robust evidence was found that the discourses on Y2K and legacy systems and the four related innovation concepts (MRP II, BPR, CRM, and SCM) had significant associations with the volume of ERP discourse between 1991 and 1999. Between October 1991 and December 2002, 201 periodicals published 2,270 articles on ERP in ABI. Table 2 shows the descriptive statistics of the 17 variables. ERP article count (Variable 1) is the dependent variable. On average, each periodical published 0.81 article on ERP in each quarter with large variations. Among the control variables (Variables 2-6), Academic (Variable 3) and US (Variable 5) are dummies. On average, these periodicals were in business for about 46 years, mostly USbased, non-academically oriented, and published approximately 18 times a year. Variables 7 through 17 are independent variables representing the two factors: problem discourses (Variables 7-10) and discourses on other IT concepts (Variables 11-17) . TQM evoked the largest volume, while the information fragmentation problem discourse was the smallest. Table 3 shows that most correlations between independent variables and the dependent variable are small but statistically significant. The correlations between several pairs of independent variables are quite high, especially those between information fragmentation (Variable 7) and operational inefficiency (Variable 8) and between Y2K (Variable 9) and legacy systems (Variable 10). So I calculated variance inflation factors (VIF) to check on multicollinearity. 13 The VIFs for four variables exceeded 5, a threshold for multicollinearity concern (Menard, 1995) : information fragmentation (5.43), operational inefficiency (5.33), Y2K (6.32), and legacy systems (5.48). Although these VIFs are still well below 10, another frequently cited threshold (Hair et al., 1995) , I chose to include only one variable from each highly correlated pair in the subsequent regression analysis. As shown in the regression results below, one half of the regression models included information fragmentation and Y2K; the other half included operational inefficiency and legacy systems. After dropping highly correlated variables, the VIFs for all explanatory (control and independent) variables in every regression model were below 3, well below the recommended threshold for multicollinearity concern.. 13 As will be discussed later in this section, most estimated coefficients are stable in magnitude, direction, and statistical significance across various regression models. In this situation, high correlations among several independent variables may, at most, inflate the standard errors of coefficients, making the evaluation of significance more conservative. 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 To test the hypotheses, I have chosen to examine one IT innovation concept as an initial step to understand the making of popularity. If support is found, tests using discourses on other concepts should be in order. The copiousness of innovation concepts in IT poses a challenge: which concept to study? Following Benbasat and Zmud's (1999) suggestion to increase the relevance of IT research, the concept to be studied should be relatively current and represent an innovation with significant market size. Additionally, its popularity should have gone through the full ascendant phase and part of the descendant phase so that there is sufficient variance to be explained by the factors identified above. These criteria eliminated concepts such as material requirements planning (MRP), since it is relatively old, data administration, since its scope is relatively limited, and cloud computing, since it is quite new. ERP, in contrast, meets the above criteria. In addition, ERP was arguably the most popular IT innovation in the 1990s (Robey et al., 2002) and potentially even the 20th century (Wagner and Newell, 2006) . Further, since its origination, the term ERP has consistently focused on the domain of organizational IT applications, as opposed to the Internet and e-commerce, whose use has become quite general and diffuse. Fore these reasons, I study the popularity of ERP.

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A review on vision techniques applied to Human Behaviour Analysis for Ambient-Assisted Living Human Behaviour Analysis (HBA) is more and more being of interest for Computer Vision and Artificial Intelligence researchers. Its main application areas, like Video Surveillance and Ambient-Assisted Living (AAL), have been in great demand in recent years. This paper provides a review on HBA for AAL and ageing in place purposes focusing specially on vision techniques. First, a clearly defined taxonomy is presented in order to classify the reviewed works, which are consequently presented following a bottom-up abstraction and complexity order. At the motion level, pose and gaze estimation as well as basic human movement recognition are covered. Next, the mainly used action and activity recognition approaches are presented with examples of recent research works. Increasing the degree of semantics and the time interval involved in the HBA, finally the behaviour level is reached. Furthermore, useful tools and datasets are analysed in order to provide help for initiating projects. Human Behaviour Analysis -and Understanding-(HBA, HBU) involves a wide range of investigation fields from motion detection and background extraction to expert systems and high-level abstraction behaviour models. This paper targets two purposes: On the one hand, researchers need to categorise existing works assuming a common taxonomy and a clear differentiation basis. On the other hand, as the application areas of these fields grow constantly; stable areas, like Video Surveillance, are covered thoroughly; while other more recent areas, like Ambient-Assisted Living (AAL) and ageing in place at smart home scenarios, present a lack of unifying works and recent state-of-the-art reviews. This makes initiation in these areas difficult, also because of the involvement of a wide variety of pure research areas from Artificial Intelligence to Natural Language Processing.. For this reason, this paper deals with the state-of-the-art of HBA/HBU from an Ambient Intelligence (AmI) point of view, focusing especially on indoor scenarios and techniques which are designed for AAL purposes. This way, recognition of Activities of Daily Living (ADLs) covers the main interest of this paper. Nevertheless, it is necessary to first face a classification of HBA levels, and to deal with all the necessary previous tasks.. To avoid the common difficulties present in vision-based systems (such as occlusions, view-dependent features, lightning conditions, etc.), occasionally these systems are enhanced with other sensors; mostly binary sensors and RFID labels. Therefore, although vision will be focused on mainly, other complementary sensors involved will be discussed briefly too.. The remainder of this paper is organised as follows: Section 2 goes through taxonomies which are applied by other authors and presents an abstraction, degree of semantics and time-oriented classification which is used in the rest of the paper. Section 3 deals with the lowest level, i.e. pose, gaze and motion estimation. These elements are used as action primitives in Section 4 where human actions are recognised based on video data and other sensor data fusion (RFID tags, accelerometers, etc.). Section 5 focuses on activity recognition methods which are of special interest in AAL: ADLs in indoor environments, like cooking and grooming, are recognised with different approaches detailed in that section. Finally, Section 6 deals with behaviour recognition methods that establish the highest degree of abstraction. Section 7 summarises some of the most used datasets and tools in the reviewed works that are available. This paper has covered the different levels of HBA following an abstraction, degree of semantics and time oriented classification. Going through recent examples of research works; most used and promising feature types, recognition methods and system design methodologies have been detailed. From pose, gaze and motion estimation to behaviour recognition, and following an initially defined classification, we have analysed vision and multimodal-based approaches.. Clearly, it can be seen that at the motion, pose and gaze estimation level, several methods achieve robust and high success rates. In conjunction with the action level, these show the most advanced and successful results. Nevertheless at higher levels, especially at behaviour, there is still a long way to go to achieve off-the-shelf products. Still, huge advances have been made in the last ten years. But the challenge to design and develop stable and general systems still persists, as most systems only solve specific problems in very particular environments.. Especially at the field of AAL, advances in this works are very valuable as personal autonomy and quality of life for elderly and cognitively impaired people can be improved enormously by these systems, and at the same time care costs can be reduced significantly.

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An Extreme Form of Superactivation for Quantum Zero-Error Capacities The zero-error capacity of a channel is the rate at which it can send information perfectly, with zero probability of error, and has long been studied in classical information theory. We show that the zero-error capacity of quantum channels exhibits an extreme form of nonadditivity, one which is not possible for classical channels, or even for the usual capacities of quantum channels. By combining probabilistic arguments with algebraic geometry, we prove that there exist channels 1 and 2 with no zeroerror classical capacity whatsoever, 0 ( 1 ) = 0 ( 2 ) = 0, but whose joint zero-error quantum capacity is positive, 0 ( 1 2 ) 1. This striking effect is an extreme form of the superactivation phenomenon, as it implies that both the classical and quantum zero-error capacities of these channels can be superactivated simultaneously, while being a strictly stronger property of capacities. Superactivation of the quantum zero-error capacity was not previously known. T HE zero-error capacity, introduced by Shannon in 1956, characterizes the optimal achievable communication rate of a noisy channel when information must be transmitted with zero probability of error [1] . This is in contrast with the more traditional capacity, which only demands error probabilities vanishing in the limit of many channel uses. The question of zero-error capacity (and more generally zero-error information theory [2] ) has a much more combinatorial flavor than the usual case, and has played an important role in the development of graph theory. Combinatorial optimization problems are often intractable so, perhaps unsurprisingly, the zero-error capacity is unknown even for many very simple channels.. Quantum information theory seeks to extend information theory to include information sources and communication systems where quantum effects are important. Because all physical systems are fundamentally quantum, this can be seen as an attempt to more accurately model physical information processing systems. Furthermore, expanding our notion of information to include quantum messages leads to new insights and applications, such as quantum cryptography and quantum computing. Because quantum systems are notoriously delicate, error correction is extremely important, and the capacities of a noisy quantum channel for transmitting various types of information noiselessly play a central role in the theory. In the context of zero-error quantum information theory, first studied in [3] , the central capacities are the zero-error classical and zero-error quantum capacities. A rather surprising effect has recently been discovered in the theory of quantum communication. Classically, there is a simple criterion for deciding whether a channel has nonzero capacity-any channel with some correlation between input and output has some positive capacity-and this criterion carries over to the usual classical capacity of quantum channels. However, when sending quantum information, the situation is very different. There are some quantum channels that are sufficiently noisy to have zero capacity for quantum communications, yet can still create correlations. In [4] , it was shown that there are pairs of channels with very different noise characteristics, but both with zero quantum capacity that, when used together, have a large joint quantum capacity. This superactivation is completely different from what happens in the classical case, and depends crucially on choosing entangled signal states for the joint channel.. Superactivation of classical channel capacities is easily seen to be impossible, both for the usual capacity and the zero-error capacity. If two classical channels have no correlation between input and output, so that their usual classical capacity vanishes, this will also hold for the joint channel. Similarly, if two classical channels each have the property that all pairs of inputs can lead to ambiguous outputs, so that the zero-error capacity vanishes, then the joint channel necessarily has this property too. The argument for the usual classical capacity carries over directly to the case of quantum channels; superactivation of the classical capacity of a quantum channel remains impossible. However, in [5] , it was shown that the zero-error classical capacity of a quantum channel actually can be superactivated (see also [6] , which found superactivation of the nonasymptotic one-shot zero-error classical capacity, and a weaker form of activation in the asymptotic setting). In this paper, we significantly strengthen the results and techniques in [5] . There, techniques from algebraic geometry were combined with probabilistic arguments to show that there are pairs of channels, each with vanishing zero-error classical capacity that have positive joint zero-error classical capacity when used together. Here, we find that there exist pairs of channels which each have vanishing zero-error classical capacity, as before, but when the two channels are used together they can even transmit must more delicate quantum information with zero error (indeed, only a single use of the joint channel is required). This is a particularly extreme form of superactivation, indeed it is the strongest possible form, and has not been seen previously for other capacities. It implies simultaneous superactivation of both the classical (already known from [5] ) and quantum (previously unknown) zero-error capacities of quantum channels, while being strictly stronger than either of these.. The rest of this paper is organized as follows. In the next section, we review some basic facts about quantum mechanics and algebraic geometry. Section III establishes sufficient conditions for this extreme form of superactivation, while Section IV shows that there exist channels which satisfy these conditions. Finally, Section V discusses the implications of our findings. There has been a recent surge of progress in the theory of quantum channels, especially their capacities. We now know that two uses of a quantum channel can sometimes, by using entangled signal states, transmit more than twice as much classical information as a single use [13] . This makes it likely that any expression for the classical capacity will require regularization, implying that it cannot be computed in general. We have known for some time that this is also the case for the quantum capacity [14] , but we now also know that the quantum capacity itself is nonadditive. Indeed, it exhibits the particularly extreme form of nonadditivity known as superactivation [4] . This implies that the amount of quantum information that can be sent through a channel depends on what other channels are also available. Understanding these additivity violations is now a key goal of quantum information theory.. Both manifestations of nonadditivity-regularization and nonadditive capacity-are already displayed by the zero-error capacity of classical channels [1] , [15] , [16] , though superactivation remains impossible even in the zero-error setting. Zero-error capacities have been the subject of intense study in the classical information theory literature for over half a century. They are, therefore, an interesting area in which to probe quantum channel capacities, and attempt to understand nonadditivity phenomena. Nonadditivity in the purely classical setting obviously has nothing to do with entanglement. But quantum channels display even stronger nonadditivity than their classical counterparts. In the quantum world, the presence of entanglement does lead to superactivation of the classical zero-error capacity of quantum channels [5] .. The usual classical and quantum capacities are not at all closely related. There is no reason to expect that channels displaying additivity violations for the quantum capacity will possess any interesting additivity properties for the classical capacities, or vice versa. As a consequence, the recent nonadditivity results for the usual capacities [4] , [13] required very different mathematical techniques for the two cases.. However, in the zero-error setting, this study shows a striking nonadditivity phenomenon that connects the classical and quantum capacities. We have proven the existence of pairs of channels that, individually, cannot communicate any information with zero error, even classical information. But, when used together, even a single use of the joint channel suffices to communicate all forms of information, quantum and classical. These channels, therefore, exhibit the most extreme possible form of additivity violation; their zero-error capacities simultaneously violate additivity for both classical and quantum information, and in the most extreme way (superactivation) to boot. This extreme form of superactivation is trivially impossible for classical channels, or for the usual capacities of quantum channels. Zero-error communication, therefore, provides a compelling setting in which to explore nonadditivity phenomena in quantum information theory.

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Object recognition using proportion-based prior information: Application to fisheries acoustics This paper addresses the inference of probabilistic classification models using weakly supervised learning. The main contribution of this work is the development of learning methods for training datasets consisting of groups of objects with known relative class priors. This can be regarded as a generalization of the situation addressed by Bishop and Ulusoy (2005) , where training information is given as the presence or absence of object classes in each set. Generative and discriminative classification methods are conceived and compared for weakly supervised learning, as well as a nonlinear version of the probabilistic discriminative models. The considered models are evaluated on standard datasets and an application to fisheries acoustics is reported. The proposed proportionbased training is demonstrated to outperform model learning based on presence/absence information and the potential of the non-linear discriminative model is shown.► Weakly supervised learning deals with prior annotation of objects in images. ► Classification model must be assessed by using probabilities. ► Reported results promote discriminative. In object recognition and classification, most of the research effort was initially dedicated to supervised learning, i.e. solving classification problems for which a dataset of labelled objects exists. Unsupervised learning has also encountered a great interest when no prior knowledge on object classes is available in the training dataset (Hinton and Sejnowski (1999) ). In a number of applications however the training set comprises some information on object classes but not all objects may be labelled. Typical examples, often referred to semi-supervised or partially-supervised cases, involve training sets in which only a subset of the objects are labelled (Chapelle et al. (2006) ). The development of reliable methods for object classification and recognition in images is an active area of research. In this paper, a probabilistic 335 method is proposed to address weakly supervised learning with training information provided as the relative proportions of object classes in images. An application to fisheries acoustics data has been considered to learn fish school classifier in acoustic echograms from the estimation of the relative species in trawl catches. Our contribution is three-fold: the extension of genera-

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User-Space Auto-Tuning for TCP Flow Control in Computational Grids With the advent of computational grids, networking performance over the wide-area network (WAN) has become a critical component in the grid infrastructure. Unfortunately, many high-performance grid applications only use a small fraction of their available bandwidth because operating systems and their associated protocol stacks are still tuned for yesterday's network speeds. As a result, network gurus undertake the tedious process of manually tuning system buffers to allow TCP flow control to scale to today's WAN environments. And although recent research has shown how to set the size of these system buffers automatically at connection set-up, the buffer sizes are only appropriate at the beginning of the connection's lifetime. To address these problems, we describe an automated and lightweight technique called Dynamic Right-Sizing that can improve throughput by as much as an order of magnitude while still abiding by TCP semantics. We show the performance of two user-space implementations of DRS: drsFTP and DRS-enabled GridFTP. q TCP has entrenched itself as the ubiquitous transport protocol for the Internet, as well as for emerging infrastructures such as computational grids [1, 2] , data grids [3, 4] , and access grids [5] . However, parallel and distributed applications running stock TCP configurations perform abysmally over networks with large bandwidthdelay products (BDP) such as are typical in grid-computing environments and satellite networks [6 -8] .. As noted in Refs. [6] [7] [8] [9] , congestion-and flow-control adaptation bottlenecks are the primary reason for this abysmal performance. The former is a topic of active research beyond the scope of this paper [10] [11] [12] . In order to address the latter problem, grid and network researchers continue to manually tune buffer sizes to keep the network pipe full [7, 13, 14] , and thus achieve acceptable wide-area network (WAN) performance in support of grid computing. However, the tuning process can be quite difficult, particularly for users and developers who are not network experts. It involves calculating the bandwidth of the bottleneck link and the round-trip time (RTT) for a given connection. The optimal TCP buffer size is equal to the product of the bandwidth of the bottleneck link and the RTT, i.e. the effective BDP of the connection.. Currently, in order to tune buffer sizes appropriately, the grid community uses diagnostic tools to determine the RTT and the bandwidth of the bottleneck link. Such tools include pipechar [15] , nettimer [16] , nettest [17] , pchar [18] , iperf [19] and netspec [20] . However, none of these tools include a client API so applications can tune their TCP connections and all of the tools require a certain level of network expertise to install and use. Furthermore, many of these tools 'pollute' the network with extraneous (probe) packets.. To simplify the tuning process, several services that provide clients with appropriate tuning parameters for a given connection have been proposed, e.g. AutoNcFTP [21] , Web100 [22] and Enable [23] , in order to eliminate what has been called the wizard gap [24] . (The wizard gap is the difference between the performance that a network 'wizard' can achieve by appropriately tuning buffer sizes and the performance of an untuned application.) Although these services provide good first approximations and can improve overall throughput by 2-5 times over a stock TCP implementation, they only measure the bandwidth and delay at connection set-up time. This makes the implicit assumption that the bandwidth and RTT of a given connection will not change significantly over the course of the connection. In Section 2, we demonstrate that this assumption is tenuous at best.. Computer Communications 27 (2004) [1364] [1365] [1366] [1367] [1368] [1369] [1370] [1371] [1372] [1373] [1374] www.elsevier.com/locate/comcom A more dynamic approach to optimizing communication in a grid involves automatically tuning buffers over the lifetime of the connection, not just at connection set-up. At present, there exist two kernel-level implementations: autotuning [25] and dynamic right-sizing (DRS) [26 -28] .. Auto-tuning implements sender-based flow-control adaptation by fairly sharing buffer space on the sender. (It assumes that receivers always have enough buffer space.) DRS, on the other hand, implements receiver-based flowcontrol adaptation by sizing the flow-control window (fwnd) according to both the buffer space on the receiver and the available bandwidth in the network. (DRS makes no assumptions about the buffer space on the sender. A sender without sufficient buffer space is allowed to transmit at a slower rate than indicated by the fwnd of the receiver.) Because auto-tuning does not take into account available buffer space on the receiver when sending packets, it allows the sender to (potentially) overrun the receiver, either inadvertently (during a FTP transfer) or maliciously (during a denial-of-service attack). DRS, on the other hand, is fully compatible with regular TCP. 2 Live WAN tests show that DRS in the kernel can achieve a 30-fold increase in throughput when the network is uncongested, although speed-ups of 7 -8 times are more typical. Achieving large speed-ups requires DRS to be installed on every pair of communicating hosts in a grid. On the other hand, it also benefits all TCP-based applications, e.g. FTP, multimedia streaming and WWW, not just grid applications.. Installing DRS requires knowledge about modifying, recompiling and installing an operating system (OS) kernel, along with root privilege to do so. Thus, DRS functionality is generally not accessible to the typical end user. While we anticipate that DRS will be incorporated into vendor's kernels so that it is transparent to the end user, users want improved performance now. Thus, we present two portable user-space implementations of DRS: drsFTP [29] and DRSenabled GridFTP.. drsFTP is similar in many ways to NLANR's AutoNcFTP [30] . Both are modified FTP implementations, which adjust buffer sizes to increase performance. The differences are two-fold. First, AutoNcFTP relies on Nc-FTP [31] whereas drsFTP uses the de-facto standard FTP daemon originally from Washington University in St Louis [32] and the open-source NetkitFTP client [33] . Second, the buffers in AutoNcFTP are only tuned at connection set-up while drsFTP buffers are dynamically tuned over the lifetime of the connection to provide better adaptation and better overall performance.. The increased performance obtained from drsFTP (Section 6.1) motivates us to integrate DRS into GridFTP [34] , a subsystem of the Globus Toolkit [35] for managing bulk-data transfers in grids. The results of the experiments conducted so far indicate that DRS, both kernel-and user-space, is likely to perform well in the real world. Anecdotally, we have observed very good performance on live networks but still need to rigorously quantify the improvements. We need to do more testing on connections with low and medium BDP. We also need to test DRS with varying amounts of cross traffic.. Although we have shown preliminary results which indicate that DRS is complementary to parallel streams as a means of increasing throughput for large data transfers, the interaction between DRS and parallel streams needs to be better characterized. Does DRS subsume the need for parallel streams or should a combined approach, as we implemented in GridFTP, be used? The results seem to indicate that a hybrid approach will yield the best performance for the fewest numbers of streams (and hence OS resources).. Finally, we are working to get DRS incorporated into the official Linux source tree. Once incorporated, applications will transparently see an increase in delivered bandwidth. In the meantime, we are continuing to develop drsFTP and GridFTP. This paper makes a number of significant contributions to the high-speed networking and grid-computing communities. First, we demonstrated that the BDP can vary widely over the lifetime of a connection. Therefore, simply tuning buffers at connection set-up is not good enough; they must be tuned over the lifetime of the connection. This is the motivation for DRS.. Further, since we used nettimer to measure the BDP of a connection, our estimates may be conservative because nettimer measures static bottleneck bandwidth and dynamic delay. With the recent release of pathload [40] , which measures dynamic available bandwidth and delay, our initial tests indicate that the BDP actually fluctuates by an additional order of magnitude.. Second, we illustrated how a receiver can measure the bandwidth and RTT of a connection (i.e. BDP) without 'polluting' the network with extraneous probing packets. The BDP value is then used as an upper bound for the flowcontrol window in DRS.. Third, in the context of DRS, we have shown how a TCP receiver can determine the approximate size of the sender's congestion window so that the receiver can advertise a flow-control window that neither needlessly constraints throughput nor unnecessarily over-allocates buffer space. Furthermore, this can be done automatically and transparently while abiding by TCP semantics. We have shown how it can be done in user space and have implemented it in drsFTP.. Fourth, we have demonstrated DRS support for grid computing by extending the GridFTP application. Unfettered by constraints imposed by the FTP specification, we have extended GridFTP to support three-party, parallel and striped transfers that are ubiquitous in grids computing.. Finally, we are making our implementations of DRS available under an open-source license. The DRS kernel implementation has already been incorporated into the Web100 project [41] . We are also working to fold the modifications necessary to support DRS into the GridFTP code base. TCP relies on two mechanisms to set its transmission rate: flow control and congestion control. Flow control ensures that the sender does not overrun the receiver's available buffer space (i.e. a sender can send no more data than the size of the receiver's last advertised flow-control window), while congestion control ensures that the sender does not overrun the network's available bandwidth. TCP implements these mechanisms via a flow-control window (fwnd) that is advertised by the receiver to the sender and a congestion-control window (cwnd) that is adapted by the sender based on the inferred state of the network.. Specifically, TCP calculates an effective window, ewnd¼ minðfwnd;cwndÞ; and then sends data at a rate of ewnd/RTT, where RTT is the round-trip time of the connection. The cwnd varies dynamically as the network state changes; however, the fwnd has traditionally been static despite the fact that today's receivers are not nearly as buffer-constrained as they were 20 years ago. Ideally, fwnd should vary with the BDP of the network, thus providing the motivation for DRS.. Historically, a static fwnd sufficed for all communication because the BDP of networks was small. Hence, setting fwnd to small values produced acceptable performance while wasting little memory. Today, most OS set fwnd < 64KB-the largest window available without scaling [36] . Yet BDPs range between a few bytes (56 Kbps £ 5 ms ! 36 B) and a few megabytes (622 Mbps £ 100 ms ! 7.8 MB). In the former case, the system wastes over 99% of the allocated buffer space (i.e. 36 B/64KB ¼ 0.05%). In the latter case, the system potentially wastes up to 99% of the network bandwidth (i.e. 64KB/7.8 MB ¼ 0.80%).. Over the lifetime of a connection, bandwidth and delay change (due to transitory queuing and congestion) implying that the BDP also changes. We use nettimer to quantify how much they change. (Although we would have like to sample at the granularity of the RTT, the overhead of running nettimer and other tools in user space prevent us from obtaining the measurements we seek.) Fig. 1 Based on the above results, the BDP over the lifetime of a connection is continually changing. Therefore, a fixed value for fwnd is not ideal; selecting a fixed value forces an implicit decision between (1) under-allocating memory and under-utilizing the network or (2) over-allocating memory and wasting system resources. Clearly, the grid community needs a solution that dynamically and transparently adapts fwnd to achieve good performance without wasting network or memory resources. In this section, we present results for both drsFTP and DRS-enabled GridFTP. In particular, we will show that the throughput improves by over 600%.

O B O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O


A simple calculus for proteins and cells The use of process calculi to represent biological systems has led to the design of different calculi such as brane calculi [1] and κ-calculus [3] . Both have proved to be useful to model different types of biological systems.As an attempt to unify the two directions, we introduce the bioκ-calculus, a simple calculus for describing proteins and cells, in which bonds are represented by means of shared names and interactions are modelled at the domain level. Proteinprotein interactions have to be at most binary and cell interactions have to fit with sort constraints.We define the semantics of bioκ-calculus, analyse its properties, and discuss its expressiveness by modelling two significant examples: a signalling pathway and a virus infection. One problem when dealing with molecular biology is to extract a functional meaning out of the mass of current knowledge. This problem has pleaded for the development of specific tools that describe biology in a faithful way. Among these tools, process algebras have been proved powerful enough to formalise the interactions, to render in a natural way the massive parallelism and concurrency of interactions, and to analyse the overall behaviour.. Two different process algebraic developments in particular brought some interest and various results. A first approach based on the π-calculus [7] and following principles proposed in [8] uses shared names to represent bonds between proteins. One of those calculi -the κ-calculus [3] -showed to be very convenient for representing mechanisms such as signalling pathways or regulatory networks. Another family of calculi -the brane calculi -proposed in [1] by relying on Mobile Ambient [2] , used action and co-action capabilities located on the surface of cell membranes. Such calculi demonstrated to be suitable for representing molecular transport as well as virus infections.. As these calculi turn out to commit to very different paradigms, it seems compelling to develop a unified framework able to handle the two kinds of the calculus accounting for translocations and phagocytosis. Section 5 draws few concluding remarks and hints at possible future works. Proofs are omitted for fitting with space limits.

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Accuracy and conservation properties of a three-dimensional unstructured staggered mesh scheme for fluid dynamics A three-dimensional unstructured mesh discretization of the rotational from of the incompressible Navier-Stokes is presented. The method uses novel and highly efficient algorithms for interpolating the velocity vector and constructing the convention term. The resulting discretization is shown to conserve mass, kinetic energy, and vorticity to machine precision both locally and globally. The spatial accuracy of the method is analyzed and found to be second order on regular meshes and first order on irregular meshes. The numerical efficiency, accuracy, and conservation properties of the method are tested on three-dimensional meshes and found to be in agreement with theory. c 2002 Elsevier Science The staggered mesh discretization referred to in this work is a discretization scheme where pressure and other scalar quantities, such as thermodynamic variables, are stored at cell centers but the velocity vector is distributed to cell faces. Each face stores only the normal component of velocity at that face. Because every three-dimensional cell contains at least four nonparallel faces, the velocity vector can always be recovered from face normal components. This recovery or interpolation of the velocity vector from the face normal components is not unique and it is a defining characteristic of various staggered mesh schemes. As will be shown in this text, particular interpolations can lead to important properties for the overall solution method. The primary difficulty of constructing conservation proofs of vector derived quantities, such as vorticity or kinetic energy, is in determining the correct Harlow and Welch [1] first described a Cartesian mesh implementation of the staggered mesh discretization in 1965. Their motivation was primarily the simplicity with which the incompressibility constraint can be implemented from within this framework. An important property of the method, which makes it popular even to this day, is the fact that discretizations of the incompressible Navier-Stokes equations that are based on this staggering scheme do not display spurious pressure modes. No particular treatment of the pressure is required to remove the red/black uncoupling found in colocated finite volume methods or the pressure locking found in some finite element and Lagrangian methods. Subsequently, it was realized that the staggered mesh approach had attractive conservation properties. While mass and momentum conservation are typically imposed explicitly via the discrete equations, Lilly [2] showed that Cartesian staggered mesh methods also conserve vorticity (or circulation in three dimensions) and conserve kinetic energy in the absence of viscosity. Perot [3] has recently shown in a two-dimensional setting that unstructured staggered mesh methods can also obtain such conservation properties. The conservation properties of a numerical method can be an indication of the methods underlying physical accuracy. As a result, staggered mesh methods are also popular in physically demanding situations such as the direct numerical simulation (DNS) of turbulence [4] [5] [6] and the large eddy simultation (LES) of turbulence [7] . The dynamic subgrid scale models used in LES appear to be particularly sensitive to the kinetic energy conserving properties of a numerical method [8] , and as such, are a primary motivation for this particular research investigation.. The generalization of staggered mesh methods to unstructured meshes was proposed by Nicolaides [9] and separately by Porshing [10] . The enhanced utility to be gained by using unstructured meshes in complex geometries is obvious. However, the extension of unstructured staggered mesh methods to an unstructured mesh setting is more complex than it might first appear. On a Cartesian mesh, cell and face centers are relatively unambiguous. On a three-dimensional unstructured mesh, which is typically a collection of irregular tetrahedra, numerous possibilities for cell and face centers exist, resulting in a host of different staggering possibilities. This work will describe a method that uses circumcenters as the defining cell and face locations.. The attractive properties of both the Cartesian and unstructured staggered mesh methods can be traced back to the fundamental mathematical properties of the discrete difference and averaging operators. The operators have symmetry properties (such as the discrete divergence is the transpose of the discrete gradient), have operator orthogonality properties (such as the discrete curl of a discrete gradient is always zero), and satisfy discrete chain rule identities (such as discrete integration by parts analogs). These mathematical properties are relatively easy to show in a Cartesian setting. Nicolaides [11] demonstrated how the first two types of properties can be obtained for unstructured meshes through the use of cell circumcenters. Perot [3] has recently shown how chain rule identities for unstructured staggered mesh methods can be obtained using appropriately defined interpolation schemes.. This work will analyze the conservation properties and accuracy of a three-dimensional unstructured staggered mesh scheme. The scheme is described in Section 2. Its conservation properties are analyzed in Section 3, and accuracy is evaluated in Section 4. Numerical tests of the accuracy and conservation are presented in Section 5, and a 3D driven cavity problem is used to test this scheme in Section 6. A discussion of the method and its relationship to other schemes is found in Section 7. The Cartesian staggered mesh scheme of Harlow and Welch [1] remains a popular scheme for the solution of the incompressible Navier-Stokes equations to this day. This is perhaps because the scheme displays a remarkable number of very attractive mathematical, physical, and practical properties. This work presents a generalization of the staggered mesh scheme to general unstructured three-dimensional meshes that displays many of these same mathematical, physical, and practical attributes. It requires low memory storage, uses very compact interpolation and discretization operators, and conserves important physical parameters beyond the primary discretization variables. The accuracy of the unstructured implementation is equivalent to the standard Cartesian staggered mesh method-first order on arbitrary meshes but effectively second order on reasonably smooth meshes and practical mesh sizes.. Other unstructured staggered mesh schemes exist in the literature [16, 17] , even for three-dimensional problems [18] [19] [20] . These methods can differ in numerous ways but the fundamental differences appear to be in how vectors (particularly velocity) are interpolated from component information and what form of the Navier-Stokes equations the discretization is based on. This work describes a number of novel interpolation schemes and describes how they lead to conservation properties. It also describes a discretization based on the rotational form of the Navier-Stokes equations whereas all other previous work has focused on discretizations starting from the divergence form of the governing equations. It is entirely possible that other interpolations and other schemes also display conservation properties. Previous work [3] shows that this is certainly the case in two dimensions. It is hoped that the new methods for analyzing accuracy and conservation that are developed in this work will aid in the analysis of other unstructured staggered mesh methods. The fact that this method can be shown to be equivalent to an unstaggered control volume discretization of the vorticity equation (Section 3.2) suggests that it is closely related to streamfunction-vorticity or velocity-vorticity methods. There is a strong connection, but also some very fundamental differences. The present formulation poses all boundary conditions on the velocity or the pressure. Unlike streamfunction-vorticity methods, boundary conditions on the vorticity or the streamfunction are not required. In addition, because the method really only advances the component of vorticity along mesh edges, the cost of the method does not triple when going from two dimensions to three dimensions, as is the case with standard streamfunction-vorticity methods. The underlying reason for these very significant differences is because the vorticity vector is a derived, rather than a primary variable. Alternatively, the distinction is the fact that the equations were discretized first and then manipulated into a vorticity-like form, rather than analytical manipulation of the exact equations into a vorticity equation followed by discretization.. The major limitations of the proposed scheme are its low-order accuracy (effectively second order), and the reliance on cell circumcenters and the local orthogonality properties of the Delaunay dual mesh. Current research is directed toward increasing the accuracy of the discrete operators, and allowing the use of nonorthogonal dual meshes such as the median dual mesh which connects cell and face centroids.

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An automated, yet interactive and portable DB designer Tuning tools attempt to configure a database to achieve optimal performance for a given workload. Selecting an optimal set of physical structures is computationally hard since it involves searching a vast space of possible configurations. Commercial DBMSs offer tools that can address this problem. The usefulness of such tools, however, is limited by their dependence on greedy heuristics, the need for a-priori (offline) knowledge of the workload, and lack of an optimal materialization schedule to get the best out of suggested design features. Moreover, the open source DBMSs do not provide any automated tuning tools.This demonstration introduces a comprehensive physical designer for the PostgreSQL open source DBMS. The tool suggests design features for both offline and online workloads. It provides close to optimal suggestions for indexes for a given workload by modeling the problem as a combinatorial optimization problem and solving it by sophisticated and mature solvers. It also determines the interaction between indexes to suggest an effective materialization strategy for the selected indexes. The tool is interactive as it allows the database administrator (DBA) to suggest a set of candidate features and shows their benefits and interactions visually. For the demonstration we use large realworld scientific datasets and query workloads. Database Management Systems (DBMSs) have been widely deployed the last years and the more complicated the database applications become the more important the physical design is. Selecting indexes, materialized views, horizontal and vertical partitions that can enhance performance in a workload is a challenging optimization problem especially if storage resources are limited. Manual physical design is both time consuming and very tedious, as the DBA needs to find the benefits of individual design features. Thus, the need for automating physical design tools has become more demanding than ever.. There are several commercial tools that offer automating tuning with several features [1] [3] [10] . These tools are based on greedy heuristics. They allow what-if design exploration and have useful user interface. Although these greedy heuristics make the existing design tools practical, they prune away large fractions of the search space and often suggest locally optimal solutions instead of the globally optimal one. On the other hand, little work has been done in providing similar tools for open source DBMSs, such as PostgreSQL and MySQL. Thus, one has to face the dilemma of selecting an expensive commercial DBMS that provides automating tools or an open source DBMS whose lack of automated tools might increase the operational cost in the long run. In addition, in the real world, the queries running on a database evolve over time. Thus, the suggested physical designs may become obsolete and require re-optimizations. Since the reoptimization is expensive, it is desirable to have a lightweight online tuning tool to monitor the query evolution and frequently to optimize the design. Finally, since the design features, such as indexes, typically take considerable amount of time to build, it is essential to schedule their construction in a way that maximizes their benefits.. We address the above requirements by developing an automated and interactive physical design tool for the PostgreSQL open source DBMS. Our tool incorporates miscellaneous algorithms and techniques to improve overall performance and provided features. Given a database, a set of queries and resource constraints, our tool suggests a near optimal configuration. It uses CoPhy [4] to suggest the indexes. CoPhy develops a convex combinatorial optimization formulation for the problem of suggesting indexes and then employs mature existing techniques to solve it. CoPhy allows to trade off execution time against the quality of the suggested solutions. The tool uses AutoPart [8] to suggest optimal partitions for the workload. It also incorporates a lightweight online physical designer-COLT [11] -to monitor the performance of the queries and suggest changes to the physical design when the existing design is suboptimal for the workload. It also suggests an effective materialization schedule for the suggested indexes using their interactions [12] . Finally, it makes the design selection process more interactive by allowing the DBA or a novice user to specify a candidate set of indexes and study the benefit of these indexes efficiently by using simulated what-if indexes, and visualizing their interactions. The user can Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. also control the physical design search by suggesting a candidate set of indexes as the starting point of the search algorithm in the designer.. In this demonstration, we use PostgreSQL because of its popularity and its relatively mature cost-based optimizer. However, the tool is designed so that it can be ported to any relational DBMS, which offers a query optimizer, a way to extract and create statistics, and control over join operations. To run the aforementioned diverse techniques on PostgreSQL, we modify the query optimizer to add what-if capabilities. The what-if capabilities simulate the original design features without actually building them, hence enabling efficient exploration of the feature space. We then extend the INUM [9] cache-based cost model to cache table partitions and partial plans to further increase the efficiency of the selection tool by orders of magnitude. Figure 1 . System Architecture Demonstration Structure: This demonstration presents a new tool which extends PostgreSQL by adding automatic physical design features. Because scientific datasets are usually very big and involve complex queries, we demonstrate the effectiveness of the tool using a real-world SDSS [13] dataset and query workload. We demonstrate three physical design scenarios. In the first scenario, the DBA manually selects the combination of design features and the tool determines the benefit of using that combination. The second one finds the optimal indexes and partitions for a given query workload. It also suggests a schedule to implement the suggested indexes. The last one continuously monitors the performance of the DBMS under incoming queries, and suggests new indexes when the indexes offer sufficient workload speedup.. The rest of the paper is organized as follows: Section 2 presents the related work; Section 3 describes the system architecture; Section 4 presents the demonstration scenarios; and Section 5 concludes the paper. In this demonstration, we presented a new automating physical design tool for open source DBMSs. The tool uses what-if analysis to simulate potential changes to the schema and integrates algorithms for suggesting indexes and partitions. It can modify the schema if there is a change in the workload, visualize interaction between indexes and present a materialization schedule for indexes. We demonstrate the tool on three different scenarios using scientific datasets and present the functionality using the tool's interface. Researchers propose several techniques for automated physical design. Due to space limit, we list only the recent commercial automated physical design tools, such as the Data Tuning Advisor (DTA) for SQL Server [1] , the Design Advisor for DB2 [14] , and the SQL Access Advisor for Oracle [10] . These commercial tools use what-if design features [5] , scale by pruning away the space in greedy manner, and do not support online physical design.. The automated physical designers for open source DBMSs are relatively new compared to commercial ones. Monterio et al. implement and design an index suggestion tool for PostgreSQL [7] . They, however, assume the size of the indexes to be zero, which severely affects the accuracy of the optimizer when what-if indexes are used. Kao et al. propose changing the optimizer to store the access paths and suggest the frequently requested access paths [6] . This, however, requires drastic changes to the optimizer, and does not explore new access paths.. Similar to COLT, Bruno et al. suggest online index tuning [2] . They, however, use proprietary interfaces with SQL Server, which are not portable to PostgreSQL and they also provide a heuristic method for index interaction, but Schnaitter et al. [12] extends the concept by comprehensively analyzing its properties and providing algorithms to schedule the suggested indexes.

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