Monthly Archives: April 2017

The clutter in online conversations

From Reddit to Quora, discussion forums can be equal parts informative and daunting. We’ve all fallen down rabbit holes of lengthy threads that are impossible to sift through. Comments can be redundant, off-topic or even inaccurate, but all that content is ultimately still there for us to try and untangle.

Sick of the clutter, a team from MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) has developed “Wikum,” a system that helps users construct concise, expandable summaries that make it easier to navigate unruly discussions.

“Right now, every forum member has to go through the same mental labor of squeezing out key points from long threads,” says MIT Professor David Karger, who was senior author on a new paper about Wikum. “If every reader could contribute that mental labor back into the discussion, it would save that time and energy for every future reader, making the conversation more useful for everyone.”

The team tested Wikum against a Google document with tracked changes that aimed to mimic the collaborative editing structure of a wiki. They found that Wikum users completed reading much faster and recalled discussion points more accurately, and that editors made edits 40 percent faster.

Karger wrote the new paper with PhD students Lea Verou and Amy Zhang, who was lead author. The team presented the work last week at ACM’s Conference on Computer-Supported Cooperative Work and Social Computing in Portland, Oregon.

How it works

While wikis can be a good way for people to summarize discussions, they aren’t ideal because users can’t see what’s already been summarized. This makes it difficult to break summarizing down into small steps that can be completed by individual users, because it requires that they spend a lot of energy figuring out what needs to happen next. Meanwhile, forums like Reddit let users “upvote” the best answers or comments, but lack contextual summaries that help readers get detailed overviews of discussions.

Wikum bridges the gap between forums and wikis by letting users work in small doses to refine a discussion’s main points, and giving readers an overall “map” of the conversation.

Readers can import discussions from places such as Disqus, a commenting platform used for publishers like The Atlantic. Then, once users create a summary, readers can examine the text and decide if they want to expand the topic to read more. The system uses color-coded “summary trees” that show topics at different levels of depth and lets readers jump between original comments and summaries.

Creative approaches to connectivity

Daniel Zuo came to MIT with a plan: He wanted to study algorithms and one day to become a research professor.

The senior has more than accomplished the former goal, conducting innovative research on algorithms to reduce network congestion, in the Networks and Mobile Systems group at MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL). And, as he graduates this spring with a bachelor’s degree in computer science and electrical engineering and a master’s in engineering, he is well on his way to achieving the latter one.

But Zuo has also taken some productive detours from that roadmap, including minoring in creative writing and helping to launch MakeMIT, the nation’s largest “hardware hackathon.”

The next step in his journey will take him to Cambridge University, where he will continue his computer science research as a Marshall Scholar.

“The Marshall affords me the opportunity to keep exploring for a couple more years on an academic level, and to grow on a personal level, too,” Zuo says. While studying in the Advanced Computer Science program at the university’s Computer Laboratory, “I’ll be able to work with networks and systems to deepen my understanding and take more time to explore this field,” he says.

Algorithms to connect the world

Zuo fell in love with algorithms his first year at MIT. “It was exactly what I was looking for,” he says with a smile. “I took every algorithms course there was on offer.”

His first research experience, the summer after his freshman year, was in the lab of Professor Manolis Kellis, head of the Computational Biology group at CSAIL. Zuo worked with a postdoc in Kellis’ group to use algorithms to identify related clusters of genes in a single cell type within a specific tissue. “We ended up coming up with a pretty cool algorithm,” he says.

As a research assistant for TIBCO Career Development Assistant Professor Mohammad Alizadeh, Zuo is now working on cutting-edge algorithms for congestion control in networks, with a focus on “lossless” data networks.

Modern computer network applications need to be able to transmit large amounts of data quickly, without losing information. Zuo likens the situation to a congested traffic light. When there are too many messages queuing at the light, some information just gets dropped.

“When the traffic light starts to get too full, I can send a packet back upstream that says ‘Wait, if you’re going to send me something, don’t,’” he explains. But sending that signal can create a new problem: a “back-propagation” of even more pauses, and more congestion upstream. Zuo’s algorithms aim to solve both of these problems, ensuring that sent data are never lost and that “traffic lights” don’t become too crowded.

Communication networks from malicious hackers

Distributed planning, communication, and control algorithms for autonomous robots make up a major area of research in computer science. But in the literature on multirobot systems, security has gotten relatively short shrift.

In the latest issue of the journal Autonomous Robots, researchers from MIT’s Computer Science and Artificial Intelligence Laboratory and their colleagues present a new technique for preventing malicious hackers from commandeering robot teams’ communication networks. The technique could provide an added layer of security in systems that encrypt communications, or an alternative in circumstances in which encryption is impractical.

“The robotics community has focused on making multirobot systems autonomous and increasingly more capable by developing the science of autonomy. In some sense we have not done enough about systems-level issues like cybersecurity and privacy,” says Daniela Rus, an Andrew and Erna Viterbi Professor of Electrical Engineering and Computer Science at MIT and senior author on the new paper.

“But when we deploy multirobot systems in real applications, we expose them to all the issues that current computer systems are exposed to,” she adds. “If you take over a computer system, you can make it release private data — and you can do a lot of other bad things. A cybersecurity attack on a robot has all the perils of attacks on computer systems, plus the robot could be controlled to take potentially damaging action in the physical world. So in some sense there is even more urgency that we think about this problem.”

Identity theft

Most planning algorithms in multirobot systems rely on some kind of voting procedure to determine a course of action. Each robot makes a recommendation based on its own limited, local observations, and the recommendations are aggregated to yield a final decision.

A natural way for a hacker to infiltrate a multirobot system would be to impersonate a large number of robots on the network and cast enough spurious votes to tip the collective decision, a technique called “spoofing.” The researchers’ new system analyzes the distinctive ways in which robots’ wireless transmissions interact with the environment, to assign each of them its own radio “fingerprint.” If the system identifies multiple votes as coming from the same transmitter, it can discount them as probably fraudulent.

“There are two ways to think of it,” says Stephanie Gil, a research scientist in Rus’ Distributed Robotics Lab and a co-author on the new paper. “In some cases cryptography is too difficult to implement in a decentralized form. Perhaps you just don’t have that central key authority that you can secure, and you have agents continually entering or exiting the network, so that a key-passing scheme becomes much more challenging to implement. In that case, we can still provide protection.

“And in case you can implement a cryptographic scheme, then if one of the agents with the key gets compromised, we can still provide  protection by mitigating and even quantifying the maximum amount of damage that can be done by the adversary.”

Hold your ground

In their paper, the researchers consider a problem known as “coverage,” in which robots position themselves to distribute some service across a geographic area — communication links, monitoring, or the like. In this case, each robot’s “vote” is simply its report of its position, which the other robots use to determine their own.

The paper includes a theoretical analysis that compares the results of a common coverage algorithm under normal circumstances and the results produced when the new system is actively thwarting a spoofing attack. Even when 75 percent of the robots in the system have been infiltrated by such an attack, the robots’ positions are within 3 centimeters of what they should be. To verify the theoretical predictions, the researchers also implemented their system using a battery of distributed Wi-Fi transmitters and an autonomous helicopter.