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Communications of the ACM

71 - 80 of 225 for bentley

Real-time groupware in the browser: testing the performance of web-based networking

Standard web browsers are becoming a common platform for delivering groupware applications, but until recently, the only way to support real-time collaboration was with browser plug-ins. New networking approaches have recently been introduced - based on re-purposed techniques for delivering web pages (Comet), or integration of real-time communication directly into the browser (HTML5 WebSockets). Little is currently known, however, about whether these new approaches can support real-time groupware. We carried out a study to assess the performance of the three different networking approaches, based on a framework of groupware requirements, in several network settings. We found that web-based networking performs well - better than plug-in approaches in some cases - and can support the communication requirements of many types of real-time groupware. We also developed two groupware applications using Comet and WebSockets, and showed that they provided fast and consistent performance on the real-world Internet. Our studies show that web-based networking can support real-time collaboration, and suggest that groupware developers should consider the browser as a legitimate vehicle for real-time multi-user systems.


TEXNH trees: a new course in data structures

The TEXNH method is an approach to undergraduate computer science education that is based on cognitive constructivisim, in the sense of Piaget, and which invokes several course design directives that include re-combining art and science, problem-based learning, problem selection from the visual problem domain, and cognitive apprenticeship. The paper describes a new TEXNH course in data structures. It includes a full comparative assessment of the realized improvement in student problem solving capability and, for the first time, cognitive authenticity in problem selection, in that the course problem is a variation on a very recent research result.


A dynamic sort-based DDM matching algorithm for HLA applications

Simulation is a low-cost and safe alternative to solve complex problems in various areas. To promote reuse and interoperability of simulation applications and link geographically dispersed simulation components, distributed simulation was introduced. The High-Level Architecture (HLA) is the IEEE standard for distributed simulation. To optimize communication efficiency between simulation components, HLA defines a Data Distribution Management (DDM) service group for filtering out unnecessary data exchange. It relies on the computation of overlap between update and subscription regions, which is called “matching”. There are many existing matching algorithms, among which a sort-based approach improves efficiency by sorting region bounds before the actual matching process, and is found to outperform other existing matching algorithms in many situations. However, the existing algorithm performs matching for all regions in one round and cannot dynamically deal with a selective region modification without processing all the regions once again. Realizing that in many spatial applications, only a small subset of all regions are actually modified in each time step, this article proposes a dynamic sort-based matching algorithm to deal with this efficiently. Theoretical analysis has been carried out for the proposed algorithm and experimental results show that the proposed algorithm has significantly better performance than major existing matching algorithms at dynamic matching.


An efficient data-centric storage scheme considering storage and query hot-spots in sensor networks

In wireless sensor networks, various schemes have been proposed to efficiently store and process sensed data. Among them, the Data-Centric Storage (DCS) scheme is one of the most well-known. The DCS scheme distributes data regions and stores the data in the sensor that is responsible for the region. In this paper, we propose a new DCS based scheme, called Time-Parameterized Data-Centric Storage (TPDCS), that avoids the problems of storage hot-spots and query hotspots. To decentralize the skewed data and queries, the data regions are assigned by a time dimension as well as data dimensions in our proposed scheme. Therefore, TPDCS extends the lifetime of sensor networks. It is shown through various experiments that our scheme outperforms the existing schemes.


How routine learners can support family coordination

Researchers have detailed the importance of routines in how people live and work, while also cautioning system designers about the importance of people's idiosyncratic behavior patterns and the challenges they would present to learning systems. We wish to take up their challenge, and offer a vision of how simple sensing technology could capture and model idiosyncratic routines, enabling applications to solve many real world problems.

To identify how a simple routine learner can demonstrate this in support of family coordination, we conducted six months of nightly interviews with six families, focusing on how they make and execute plans. Our data reveals that only about 40% of events unfold in a routine manner. When deviations do occur, family members often need but do not have access to accurate information about their routines. With about 90% of their content concerning deviations, not routines, families do not rely on calendars to support them during these moments. We discuss how coordination tools, like calendars and reminder systems, would improve coordination and reduce stress when augmented with routine information, and how commercial mobile phones can support the automatic creation of routine models.


(Re)defining computing curricula by (re)defining computing

What is the core of Computing? This paper defines the discipline of computing as centered around the notion of modeling, especially those models that are automatable and automatically manipulable. We argue that this central idea crucially connects models with languages and machines rather than focusing on and around computational artifacts, and that it admits a very broad set of fields while still distinguishing the discipline from mathematics, engineering and science. The resulting computational curriculum focuses on modeling, scales and limits, simulation, abstraction, and automation as key components of a computationalist mindset.


Growing and destroying the worth of ideas

This paper presents a novel computational approach to the study of creativity. In particular, it discusses a modeling framework that addresses the worth of ideas ascribed by agents embedded in a social world. The triple objective of this system is to improve our understanding of how ideas may emerge from a few individuals, how social interaction may result in the ascription of value to new ideas, and how culture may evolve through time, transforming or replacing dominant or consensual ideas. The proposed system encompasses commonalities in existing theories of creativity, and suggests future theoretical directions that can be explored via simulation.


Agile specifications

Traditional formal methods and modern agile methods are separated more by limitations of current technology than by fundamental intellectual differences. A mixed interpreter that executes mixed programs, comprising both declarative specification statements and regular imperative statements, might bridge the gap. This paper explores how such an interpreter might be used, showing by example how it might support a variety of development activities.


Generating transparent, steerable recommendations from textual descriptions of items

We propose a recommendation technique that works by collecting text descriptions of items and using this textual aura to compute the similarity between items using techniques drawn from information retrieval. We show how this representation can be used to explain the similarities between items using terms from the textual aura and further how it can be used to steer the recommender. We describe a system that demonstrates these techniques and we'll detail some preliminary experiments aimed at evaluating the quality of the recommendations and the effectiveness of the explanations of item similarity.


Fragment, tag, enrich, and send: Enhancing social sharing of video

The migration of media consumption to personal computers retains distributed social viewing, but only via nonsocial, strictly personal interfaces. This article presents an architecture, and implementation for media sharing that allows for enhanced social interactions among users. Using a mixed-device model, our work allows targeted, personalized enrichment of content. All recipients see common content, while differentiated content is delivered to individuals via their personal secondary screens. We describe the goals, architecture, and implementation of our system in this article. In order to validate our results, we also present results from two user studies involving disjoint sets of test participants.