It was a gee-whiz innovation, a concept that would later help thousands of companies earn more money, but to John Riedl, it held a different kind of promise: Making people's lives a little better.

Riedl, a computer scientist and University of Minnesota professor, helped create the field of recommender systems, which allow computers to predict what products or articles someone might enjoy based on other people's preferences. Think Netflix. He later became an expert in social computing and systems that rely on users' contributions. Think Wikipedia.

The McKnight Distinguished Professor, passionate thinker and dedicated dad died July 15, three years after being diagnosed with melanoma. He was 51.

"He had an incredible career," said Joseph Konstan, a University of Minnesota professor who worked with Riedl for two decades. "But he was also a first-rate role model and mentor whom I think we all looked to on issues like work-life balance and how to handle adversity."

Riedl was born in Evanston, Ill., and grew up in Ohio, where his dad was a mathematics professor and later an administrator at Ohio State University.

He met his wife, Maureen, while studying at the University of Notre Dame, in the dorm she shared with his sister. He was bright, funny, intensely "interested in everything," she said. "When he looked at you, you felt like you were the most important person in the world."

Riedl's career took off in the early 1990s, with the publication of a paper, cowritten with Paul Resnick, on recommender systems — complicated computations that make use of like-minded people's opinions on films, restaurants and products.

Riedl believed in recommendations, Maureen Riedl said. "I don't think we bought a brand of dishwashing soap without checking reviews."

With that academic paper, "they created the field," said Bradley Miller, one of Riedl's former graduate students. "Back then, who knew that it was going to become what it ultimately has become."

To commercialize that research, Riedl co-founded in 1996 the company Net Perceptions, which would grow to more than 300 employees and boast a $60-a-share stock price before being crushed by the dot-com collapse.

He later worked to quantify vandals' effect on Wikipedia and build tools to encourage greater, better participation. One recent paper by his research group found that Wikipedia is overwhelmingly edited by men.

"Does it matter that women are mostly not editing the most important information resource in our world?" Riedl asked during a 2012 talk. "That seems to me really important. And the question for this community, for people with our skills, is: What can we do about it?"

Riedl himself added information on new therapies to the Wikipedia page on melanoma. He approached the disease with the same curiosity and careful study as his own research, said Maureen, who works in the U's Medical School.

Despite a dynamic career, he kept his family a priority, delving into his three children's interests. He cowrote an academic paper with his oldest son, Eric, a mathematics graduate student at Harvard University. He watched sports with Karen, 24, who is working on her Ph.D. in pharmaceutics. He learned to play video games to compete with Kevin, 22, who is studying mechanical engineering.

"It was really phenomenal," Maureen Riedl said. "We never felt we were an afterthought."

In a short speech at a gathering a few weeks before his death, Riedl asked his friends not to feel sorry for him.

"If when I was a young boy, someone had offered me the chance to live the life I've lived, given that I had to die of a brain tumor when I was 51, I would have taken it in a second," he said. "A wife to love for 28 years, three kids I'm so proud of I could just burst, a career as a famous professor, a chance to found a start-up company and now, a special group of family and friends gathered together to wish me bon voyage — what a great life."

Riedl's survivors also include his parents, John and Mary, and his siblings Ann, Jim, Steve, and Dan. Services have been held.

Jenna Ross • 612-673-7168