About

Professor John Riedl was a renowned figure in the field of recommender systems and interactive intelligent systems. He was instrumental in creating and nurturing these fields, making significant contributions that bridged research and practical application. Riedl co-founded the company Net Perceptions in 1996 to commercialize his research, growing it to over 300 employees and influencing the industry substantially. His work has been widely adopted, with software derived from his research being used by tens of thousands of businesses today. In addition to his industry impact, Riedl was a dedicated educator and mentor. He created and led practice-focused courses that provided undergraduate students with hands-on experience in designing and building interactive intelligent systems for the Web, which supported thousands of users. He was recognized with several teaching awards, including an Outstanding Teacher Award from his department, the George Taylor Award for Exceptional Contributions to Teaching from the College of Science and Engineering, and the University’s McKnight Distinguished Professorship. Riedl was deeply concerned about student welfare and was a sought-after mentor for junior faculty, contributing significantly to the academic community. His research and leadership brought invaluable visibility to his department and the University, leaving a lasting legacy in his field.

Research topics

• Sociology
• Computer Science
• Anthropology
• Electrical engineering
• Engineering
• Reliability engineering
• Electronic engineering
• Cognitive psychology
• Social psychology
• Operating system
• Psychology
• Neuroscience

Selected publications

• V-Band InAlN/GaN/SiC MMIC Amplifier Embedded by Fan Out Wafer Level Packaging Technology

  2025-09-22

  article

  The design and measurements of a GaN MMIC based on advanced technology embedded into an advanced packaging approach is presented. For this purpose, a V-band MMIC amplifier based on InAIN/GaN/SiC HEMTs technology has been designed and manufactured. We used a Fan Out Wafer Level Packaging (FOWLP) approach as a packaging solution. Intensive co-design was carried out between the chip and the package to achieve low-loss RF transitions between the PCB and the MMIC up to V-band. These results were achieved using 2D <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\frac{1}{2}$</tex> and 3D electromagnetic simulations at both the MMIC and package levels. The amplifier has a gain of around 20 dB and delivers an output power of 1 W at 55 GHz on a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$5 \times 5 ~\text{mm}^{2}$</tex> package size.

  PublisherDOI

• Reliability Assessment of Heterogeneous Integrated FOWLP Test Structure Packages for Mixed RF Digital Front-End Application

  2022 IEEE 9th Electronics System-Integration Technology Conference (ESTC) · 2024

  1st authorCorresponding
  • Computer Science
  • Reliability engineering
  • Computer Science

  Heterogeneous (GaN & GaAs) integrated FOWLP packages were fabricated and subjected to reliability testing to assess the capability of the packaging platform. Dedicated reliability test vehicles including a Ka band RF front-end (RFFE) module were fabricated to support reliability investigation. Results from thermal cycling of the daisy chain test vehicles highlight a sensitivity to 3 parameters: die technology (GaN-on-SiC or GaAs), the presence of a back side metallization, and die backside plasma cleaning. A reliability assessment of the RFFE produced satisfactory results with all stressed parts passed successfully PC-MSL3, TC, HTSL and uHAST.

  DOI

• War Versus Inspirational in Forrest Gump: Cultural Effects in Tagging Communities

  Proceedings of the International AAAI Conference on Web and Social Media · 2021 · 15 citations

  Senior authorCorresponding
  • Sociology
  • Psychology
  • Cognitive psychology

  People from different cultures vary in cognition, emotion, and behavior. We explore cultural differences in a tagging system. We developed a model of cultural differences and performed a controlled empirical study with American and Chinese subjects to investigate questions that arise from the model. American and Chinese subjects differed in many ways: the number and types of tags they applied; the extent to which they applied suggested tags or entered new tags of their own; and how often they applied tags that originated from a different culture. Our results are consistent with theories of cultural differences between Asian and Western cultures. Our findings suggest new opportunities and mechanisms for shaping user behavior to produce useful tag repositories.

  PublisherOA PDFDOI

• Potential impacts of solar arrays on regional climate and on array efficiency

  International Journal of Climatology · 2017-01-26 · 24 citations

  article

  ABSTRACT World population and industrialization have increased significantly, leading to an increase in global energy demand, mainly relying on fossil fuels. Use of alternative energy sources such as wind, hydro and solar has been steadily increasing. Australia is a vast continent which receives an average 58 million PJ of energy from the sun annually. Given this resource potential, one could envisage construction of massive solar farms to help meet energy demands. If such constructions went ahead, their potential benefits/impacts on the climate over and surrounding the solar arrays would need to be investigated. Here, we study the potential climatic impacts over and in the environment surrounding massive hypothetical solar sites across Australia using a global stretched grid atmospheric model. The solar farms are represented by modelling the effects of perturbing surface albedo and surface roughness. The sensitivity experiments incorporate different combinations of surface albedos, shapes and locations of the solar farms, with a focus on the summer season. Our study suggests that depending on array sizes, locations, orientations and surface albedo (potentially increased by means of highly reflective in‐fill material), the climate over solar arrays could be modified significantly. Over the arrays with positive albedo perturbation, rainfall would decrease by around 30–70%, and daytime maximum air temperatures would decrease up to 10 °C. In addition, solar irradiance would increase by around 5–20%, which combined with the air temperature cooling, would lead to an enhanced solar power yield up to 25%.

  PublisherDOI

• An Algorithmic Framework for Performing Collaborative Filtering

  ACM SIGIR Forum · 2017-08-02 · 2555 citations

  articleSenior author

  column Share on An Algorithmic Framework for Performing Collaborative Filtering Authors: Jonathan L. Herlocker University of Minnesota University of MinnesotaView Profile , Joseph A. Konstan University of Minnesota University of MinnesotaView Profile , Al Borchers University of Minnesota University of MinnesotaView Profile , John Riedl University of Minnesota University of MinnesotaView Profile Authors Info & Claims ACM SIGIR ForumVolume 51Issue 2July 2017 pp 227–234https://doi.org/10.1145/3130348.3130372Published:02 August 2017Publication History 63citation823DownloadsMetricsTotal Citations63Total Downloads823Last 12 Months45Last 6 weeks3 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

  PublisherDOI

• Helping Wikipedia versus Helping a WikiProject: Subgroup Dynamics in Online Production Communities

  Academy of Management Proceedings · 2017-08-01 · 1 citations

  articleSenior author

  Many online communities consist of subgroups that co-exist on the same technical platform and serve different interests or purposes. Yet we have limited knowledge of the interplay between subgroups and the large community as a whole and the trade-offs between various outcomes. Does greater contribution at the subgroup level lead to greater or lower contribution to the large community? Are members who belong to multiple subgroups more socially embedded and therefore less likely to leave? Are active contributors more or less likely to leave the community? In this paper, we analyze data from 648 WikiProjects and the archived behaviors of 14,464 member editors to address these questions. Our results reveal two critical trade-offs in managing online production communities. First, a number of factors that increase member contribution such as tenure dissimilarity and past contribution also increase one’s likelihood of leaving the community, perhaps due to conflict or feelings of “mission accomplished” or “burnout”. Second, individual membership in multiple projects has mixed and largely negative effects. It decreases the amount of work editors contribute to both the individual projects and Wikipedia as a whole. It reduces one’s likelihood of leaving individual project yet increases the likelihood of leaving Wikipedia as a whole. The study advances our understanding about the trade-offs between multiple community outcomes and the interplay between subgroups and the large community as a whole.

  PublisherDOI

• The Food Integrity Knowledge Base – a web-tool mapping analytical solutions to food fraud issues

  2015-01-01

  article
  Publisher

• The Impact and Evolution of Group Diversity in Online Open Collaboration

  Management Science · 2015-08-28 · 106 citations

  articleSenior author

  Online open collaboration efforts, such as Wikipedia articles and open source software development, often involve a large crowd with diverse experiences and interests. Diversity, on the one hand, facilitates the access to and integration of a wide variety of information; on the other hand, it may cause conflict and hurt group performance. Although diversity’s effects have been the subject of many studies in offline work groups (with the results remaining inconclusive), its effects in online self-organizing groups are underexplored. In this paper, we examine 648 WikiProjects to understand (1) how tenure disparity and interest variety affect group productivity and member withdrawal and (2) how the two types of diversity evolve over time. Our results show a curvilinear effect of tenure disparity, which increases productivity and decreases member withdrawal, up to a point. Beyond that point, productivity slightly decreases, and members are more likely to withdraw. In comparison, our results show a positive effect of interest variety on productivity and no significant effects on withdrawal. We also find that, over a project’s life cycle, tenure disparity decreases and interest variety increases, with both converging toward the level that is optimal for group performance. Overall, our study highlights the importance of having diverse experiences and perspectives in online open collaboration and the power of self-organizing that helps groups evolve toward their high-performing zones. It also has practical implications on the design of collaboration tools and new forms of organizing work in traditional organizations. This paper was accepted by Sandra Slaughter, information systems.

  PublisherDOI

• The identification of deviance and its impact on retention in a multiplayer game

  2014-02-07 · 138 citations

  articleSenior author

  Deviant behavior in online social systems is a difficult problem to address. Consequences of deviance include driving off users and tarnishing the system's public image. We present an examination of these concepts in a popular online game, League of Legends. Using a large collection of game records and player-given feedback, we develop a metric, toxicity index, to identify deviant players. We then look at the effects of interacting with deviant players, including effects on retention. We find that toxic players have several significant predictive patterns, such as playing in more competitive game modes and playing with friends. We also show that toxic players drive away new players, but that experienced players are more resilient to deviant behavior. Based on our findings, we suggest methods to better identify and counteract the negative effects of deviance.

  PublisherDOI

• More Efficient Tagging Systems with Tag Seeding

  2014-06-16

  articleSenior author

  Tags are a useful mechanism for users to find, organize, and understand items on a web site. A tagging system evolves to reflect a user community’s understanding of an information space. However, the evolution can be problematic: specif-ically, the ratio of tags to items can decrease over time, to the extent that tags no longer effectively discriminate among items. The primary reason is over application of existing popular tags to most of the items. This makes it difficult for a user to search and navigate using specific tags. We address this problem of disproportionate application of existing popular tags by eliciting applications of those tags that are under applied but highly relevant. In this paper, we introduce two metrics to identify such under applied rel-evant tags from the system. We then design a controlled study to elicit more applications of these tags, to show how the declining discriminating power of tags is counteracted by interventions in tag applications using these carefully chosen under applied tags, namely seeded tags. We found that users were able to apply these underuti-lized tags, with the result that about eleven months of lost navigational and search efficiency of the tagging system was attained back. We also monitored subsequent usage of these tags in the system and found that the seeded tags does at-tract more users in navigation (such as clicks and searches) than before our intervention, suggesting that tag seeding has a persistent effect over the system. 1

  Publisher

Recent grants

• Helping Hands: Computer Support for Community-Maintained Artifacts of Lasting Value

  NSF · $642k · 2005–2009

Frequent coauthors

• Joseph A. Konstan

  University of Minnesota

  62 shared

• Shyong K. Lam

  University of Minnesota

  28 shared

• Ernest F. Retzel

  University of Minnesota Medical Center

  19 shared

• Al Mamunur Rashid

  18 shared

• Bharat Bhargava

  Purdue University West Lafayette

  17 shared

• Shilad Sen

  Microsoft (United States)

  15 shared

• Elizabeth Shoop

  Macalester College

  14 shared

• John V. Carlis

  University of Minnesota

  14 shared

Labs

• In Memoriam: John RiedlPI

Awards & honors

• 2010 ACM Software System Award
• George Taylor Award for Exceptional Contributions to Teachin…
• McKnight Distinguished Professorship