26 June 2014 ~ 0 Comments

NetSci 2014 Report

NetSci, the top global conference about network science, never fails to be a tornado of ideas. Now that the dust has settled, I feel a bit easier to put this year’s thoughts on this post. Yes, this is yet another conference report by yours truly.

Let’s first get over the mandatory part of the report: an evaluation of the awesomeness of the Multiple Networks satellite I co-organized with my friends scattered around Europe. As said, this year’s edition was open to submissions and we received 17 of them. I think that, as a start, that is a good figure. Also, the attendance was more than satisfactory, and it appears scattered only because we got the largest room of the conference! Here’s proof!

DSC_0544.JPG

The overall event was a great success. The talks were very interesting and we had a great unexpected bonus point. One of our keynotes, as you might remember, was Mason Porter. Well, the guy actually got the Erdos-Renyi prize this year! The Erdos-Renyi prize has been established in 2012 and it goes to outstanding young researchers in network science. Well, make a note of this: speaking at the Multiple Networks satellite will eventually get you some important awards. After all, everybody knows that correlation = causation.

My favorite satellite (besides the one I organized, obviously) continues to be the Arts, Humanities and Complex Networks symposium. This year it was a little bit tougher than usual, with a lot of qualitative stuff that not everybody can appreciate. However, their keynote by Lada Adamic was nothing short of outstanding. She is currently working at Facebook, a position that gives her a privileged vantage point over memes and viral events. You know that those things tickle my curiosity very strongly, and Lada’s work is really great. She presented her work, where she proves that meme evolution and mutation on Facebook follows very closely the same mechanics of evolution and mutation we find in the biological world. Good news for my old paper, which was heading in the same direction!

Which brings me to the main conference, because one of the best talks I attended was from Jon Kleinberg, who collaborated with Lada on another memes-meet-Facebook work. In that case, there is less good news for me. My research plan is to use meme content to predict virality. However, the Kleinberg-Adamic dream team showed that content is actually a very weak factor! (Here’s a blog post about it).

There is still hope, though. My way to deal with content is fundamentally different than theirs. Plus the problem they are studying is slightly different from mine: they are analyzing memes that are already going viral and they want to know how popular they will get. I’m more focused on knowing if the meme is going to be popular at all, and I’m not that concerned about whether everybody will know it or only a niche group.

Virality of content was a very hot topic this year, because there were two other fantastic talks about it. One was by Sinan Aral, and he talked about how much we are influenced by a post’s popularity when we read it. Controlling for content (and believe me when I say that Sinan is one of the best experiment designers out there), if we know that a post is popular we are more likely to upvote it. This is so true that Reddit itself decided, for some subreddits, to hide the post score for the first few hours, so that real good content will eventually flow to the top once the discussion is settled.

On top of that, also James Gleeson talked about a theoretical model that can account for the popularity distribution of memes. The model sounds simple. You just assume that a person has a box containing all the memes they saw in the past. With some probability, the person will either come up with something new or reshare a meme from their box. When resharing from the box, there is a memory effect for which more recent memes are more likely to be reshared. Whenever you share something, regardless if it is new or not, it ends up in your friend’s boxes. Even if it looks so simple, the actual solution of the model isn’t it at all and James is so good he defies belief. And, at the end of the day, everything works like a charm. Again, this does not bother me too much, because it only predicts the distribution of popularity, not which memes are going to be popular, a different problem.

Besides all this work meme popularity, there were other very interesting talks. I mention:

  • The very elegant talk by Chris Moore on community discovery, which also has the by-product of providing witty one liners for many occasions (for example “Physicists like to minimize functions because, you know, rocks fall”);
  • The nice talk by Frank Schweitzer on the role of active individuals in collaboration networks, who have the side effect of making the networks more unstable and prone to breaking apart (damn you, hyper-active people!);
  • The usual fun of the lighting talks (they could not call them ignite talks because of copyright issues). My favorite for this year was from Max Schich, with a really great panorama of the art market in London, Paris and Amsterdam from the Getty dataset. Aaron Clauset and Roberta Sinatra deserve to be mentioned too, with two great talks about climbing the greasy pole in academia (is it really worth it to shoot for big name universities? Short answer: no).

That’s it! You can see that also this year there was a lot to see and to think about. I am already looking forward for next year!

Continue Reading

22 May 2014 ~ 0 Comments

The NetSci Multiple Networks Menu

Friends, scientists, network fanatics, lend me your eyes: I come to announce the program of the Multiple Network Modeling, Analysis and Mining symposium, introduced some months ago on these pages. To give you a quick recap: this is a satellite event which will happen at the 2014 edition of NetSci, a major network science event of the year. The symposium will take place on Monday June 2nd, while the conference itself will start on June 4th and it will last until the end of the week. Differently from last year, we now have space for contributed talks and I like the program we were able to set up. So, I’ll boast about it here.

You can find the overview of the entire event on the official website, but let me give you the highlights.

We have four invited speakers: Frank Schweitzer, Renaud LambiotteNitesh Chawla and Mason Porter. They come from different backgrounds (System Design, Mathematics and Computer Science) which is a great plus for the event. They are going to:

  • Tackle the mathematical foundations of multiple networks;
  • Describe models for multiple networks;
  • Analyse them, both in the flavour of bipartite temporal social networks and in the extension of the classic link prediction problem. Usually in link prediction we are interested in evaluating the likelihood of seeing “a” connection between two nodes. Since in multiple networks there are different types of connections, we are also interested in predicting “which” connection we will observe.

As for the contributed talks, we have a pretty good team, including (but not limited to) works signed by David Lazer from Northeastern University, Juyong Park from KAIST, Eugene Stanley from Boston University and many more. We had such a positive reaction to our call for papers, that we had to increase the slots for contributed talks from 5 to 7 and still reject presentations that we really wanted to see. Among my favourites works there are:

  • Multiple network applications to study the productivity of countries and predicting their growth;
  • The study of evolution of different relations among almost 2000 students from 14 US universities;
  • A network-based approach for ranking the performances of sport teams;
  • Novel way to classify nodes in complex networks where multiple different relations are present;
  • … and more!

For completeness, here’s the detailed schedule, I hope to see many of you there!

Session I

9.00 – 9.30 Registration / Set Up
9.30 – 9.50 Introduction: Welcome from the organizers, presentation of the program
9.50 – 10.30 Keynote I: Frank Schweitzer, Professor for Systems Design at ETH Zurich
Analysing temporal bipartite social networks
10.30- 11.00 Coffee Break

Session II

11.00 – 11.40 Keynote II: Renaud Lambiotte, Associate Professor, Department of Mathematics at University of Namur
Non-Markovian Models of Networked Systems
11.40 – 12.00 Daniel Romero, Nina Mishra and Panayiotis Tsaparas
Estimating the Relative Utility of Networks for Predicting User Activities
12.00- 13.30 Lunch

Session III

13.30 – 14.10 Keynote III: Nitesh Chawla, Associate Professor, Department of Computer Science & Engineering at the University of Notre Dame
Predicting links in heterogeneous social networks
14.10 – 14.30 Katherine Ognyanova, David Lazer, Michael Neblo, Brian Rubineau and William Minozzi
Ties that bind across contexts: personality and the evolution of multiplex networks
14.30 – 14.50 Neave O’Clery
A Multi-slice Approach to Understanding the Evolution of Industrial Complexity and Growth
14.50 – 15.30 Coffee Break

Session IV

15.30 – 16.10 Keynote IV: Mason Porter, Associate Professor at the Oxford Centre for Industrial and Applied Mathematics
Mathematical Formulation of Multilayer Networks
16.10 – 16.30 Seungkyu Shin, Sebastian Ahnert and Juyong Park
Degree-Neutralizing Weighted Random Walk Ranking in Competition Networks
16.30 – 16.50 Tomasz Kajdanowicz, Adrian Popiel, Marcin Kulisiewiecz, Przemysław Kazienko and Bolesław Szymański
Node classification in multiplex networks
16.50 – 17.10 Francesco Sorrentino
Stability of the synchronous solutions for networks with connections of different types
17.10 – 17.30 Andreas Joseph, Irena Vodenska, Eugene Stanley and Guangron Chen
MLR Fit-Networks: Global Balance of Payments

Conclusion and final announcements

17.30 – 18.00

Continue Reading

15 July 2013 ~ 0 Comments

ICWSM 2013 Report

The second half of the year, for me, is conference time. This year is no exception and, after enjoying NetSci in June, this month I went to ICWSM: International Conference on Weblogs and Social Media. Those who think little of me (not many, just because nobody knows me) would say that I went there just because it was organized close to home. It’s the first conference for which I travel not via plane, but via bike (and lovin’ it). But those people are just haters: I was there because I had a glorious paper, the one about internet memes I wrote about a couple of months ago.

In any case, let’s try to not be so self-centered now (good joke to read in a personal website, with my name in the URL, talking about my work). The first awesome thing coming to my mind are the two very good keynotes. The first one, by David Lazer, was about bridging the gap between social scientists and computer scientists, which is one of the aims of the conference itself. Actually, I have been overwhelmed by the amount of the good work presented by David, not being able to properly digest the message. I was struck with awe by the ability of his team to get great insights from any source of data about politics and society (one among the great works was about who and how people contact other people after a shock, like the recent Boston bombings).

For the second keynote, the names speak for themselves: Fernanda Viégas and Martin Wattenberg. They are the creators of ManyEyes, an awesome website where you can upload your data, in almost any form, and visualize it with many easy-to-use tools. They constantly do a great job in infographics, data visualization and scientific design. They had a very easy time pleasing the audience with examples of their works: from the older visualizations of Wikipedia activities to the more recent wind maps that I am including below because they are just mesmerizing (they are also on the cover of an awesome book about data visualization by Isabel Meirelles). Talks like this are the best way to convince you of the importance of a good communication in every aspect of your work, whether it is scientific or not.

As you know, I was there to present my work about internet memes, trying to prove that they indeed are proper memes and they are characterized by competition, collaboration, high-order organization and, maybe I’ll be able to prove in the future, mutation and evolution. I knew I was not alone in this and I had the pleasure to meet Christian Bauckhage, who shares with me an interest in the subject and a scientific approach to it. His presentation was a follow-up to his 2011 paper and provides even more insights about how we can model the life-span of an internet meme. Too bad we are up against a very influential person, who recently stated his skepticism about internet memes. Or maybe he didn’t, as the second half of his talk seems to contradict part of the first, and his message goes a bit deeper:

Other great works from the first day include a great insight about how families relate to each other on Facebook, from Adamic’s group. Alice Marwick also treated us to a sociological dive into the world of fashion bloggers, in the search of the value and the meaning of authenticity in this community. But I have to say that my personal award for the best presentation of the conference goes to “The Secret Life of Online Moms” by Sarita Yardi Schoenebeck. It is a hilarious exploration of YouBeMom, a discussion platform where moms can discuss with each other preserving their complete anonymity. It is basically a 4chan for moms. For those who know 4chan, I mean that literally. For those who don’t, you can do on of two things to understand it: taking a look or just watching this extract from 30 Rock, that is even too vanilla in representing the reality:

I also really liked the statistical study about emoticon usage in Twitter across different cultures, by Meeyoung Cha‘s team. Apparently, horizontal emoticons with a mouth, like “:)”, are very Western, while vertical emoticons without a mouth are very Eastern (like “.\/.”, one of my personal favorites, seen in a South Korean movie). Is it possible that this is a cultural trait due to different face recognition routines of Western and Eastern people? Sadly, the Western emoticon variation that includes a nose “:-)”, and that I particularly like to use, apparently is correlated with age. I’m an old person thrown in a world where young people are so impatient that they can’t lose time pressing a single key to give a nose to their emoticons :(

My other personal honorable mention goes to Morstatter et al.’s work. These guys had the privilege to access the Twitter Firehouse APIs, granting them the possibility of analyzing the entire Twitter stream. After that, they crawled Twitter using also the free public APIs, which give access to 1% of all Twitter streams. They shown that the sampling of this 1% is not random, is not representative, is not anything. Therefore, all studies that involve data gathering through the public APIs have to focus on phenomena that include less than 1% of the tweets (because in that case even the public APIs return all results), otherwise the results are doomed to be greatly biased.

Workshops and tutorials, held after the conference, were very interesting too. Particularly one, I have to say: Multiple Network Models. Sounds familiar? That would be because it is the tutorial version of the satellite I did with Matteo Magnani. Luca Rossi and others at NetSci. Uooops! This time I am not to blame, I swear! Matteo and Luca organized the thing all by themselves and they did a great job in explaining details about how to deal with these monstrous multiple networks, just like I did in an older post here.

I think this sums up pretty much my best-of-the-best picks from a very interesting conference. Looking forward to trying to be there also next year!

Continue Reading

16 June 2013 ~ 0 Comments

NetSci 2013 Report

As I mentioned a couple of months ago, during the first week of June the NetSci conference took place. NetSci is the main venue that brings together all researchers interested and involved in network science. It has always been a gigantic opportunity to put you in contact with the big shots in network analysis and an excellent playground for very interesting discussions. This year was no different.

Of course, for me the most important part of it was the very first day, when the satellite on multiple networks (organized by myself together with Matteo Magnani, Dino Pedreschi, Luca Rossi, Guido Caldarelli and Przemyslaw Kazienko) happened. As I wrote more than once in the past, multiple networks are networks in which the nodes may be connected with different kinds of interactions (friendship, collaboration, and so on).

It was an extremely interesting event; a first step to bring together many researchers working on the topic of multiple networks, most of whom hadn’t spoken to each other up until then. And when I say it was a smooth and successful operation, you don’t have to take my word for it. We have proof of a room full of brilliant minds taking up all the available spots… and beyond:

The talks were very impressive:

  • We learnt how to measure eigenvector centrality on multiple networks (and you can too);
  • We learnt how to extend basic measures from regular complex networks to multiple networks (and you can too);
  • We learnt how to mine network with heterogeneous information on nodes and edges (and you can too);
  • We learnt how to detect communities on multiple networks (and you can too);
  • We learnt how to infer the latent structure of inter-related networks (and you can too);
  • We learnt how a random walker behaves on dynamic networks (and you can too);
  • We learnt about the structure and dynamics of multiple networks (and you can too);
  • And we learnt how the properties of multiple networks arise when adding one network at a time (and you can too).

But NetSci, of course, was much more than just this satellite. Another event you absolutely didn’t want to miss there was the Arts, Humanities and Complex Networks Symposium, organized by Max Schich and Isabel Meirelles.

They are both great guys, with a gigantic knowledge about art and design. For example, they picked up a great reference for the logo of their symposium, namely one of the most known infographics made about visual arts, by Alfred Barr:

And besides the usual great lineup of talks (from the Wikidata project to a very cool movie ranking multiple network algorithm) you can learn surprising stuff about basically everything. My favorite: the observation of one of the speakers about the above visualization itself. Apparently, he was the first to realize that there is a bull up there (hint: Cubism lays in between the bull’s horns). As Max then puts it:

Then… the rest of the conference. It is impossible to even give a close idea of the overload of ideas and flashes of genius that populated the venue for those three days. I’ll work around the problem and cheat by giving you a laundry list of (a very tight subset of) the things that most impressed me during the conference:

  • The excellent invited talk by Shlomo Havlin about interdependent networks (networks which depend on each other to function, much like a computer network controlling the electric grid). This interests me because he claims that interdependent networks are a more general case of multiple networks (although I personally have an inkling that perhaps they can be reduced to the same model);
  • The usual spectacular presentation style of my friend Cesàr Hidalgo, who this time talked about a complex system showing a nested structure: namely, the cultural exports of different countries;
  • A really great contributed talk by Esteban Moro, which in my opinion could have been a keynote speech as well. Dr. Moro highlighted how people have a trade-off between social capacity (how many relationships we can keep alive) and social activity (how many new people we can meet). As a consequence, different social strategies arise;
  • A brilliant mathematical formulation of a network problem by Jure Leskovec, that, in my opinion, could be the final word about the problem itself. And it resembles the formal mathematical formulation of the same algorithmic idea behind my DEMON;
  • And the hilarious ignite talks, 5 minutes and 20 slides for each speaker. There was no possibility of interacting, with the presentation automatically jumping to the next slide every 15 seconds. Next year I definitely want to try to do one too.

And, of course, many other things. But you get the idea: blog posts about it are boring, you really have to experience it yourself.

Continue Reading