이집트는 지금..

무바락 대통령 장기 집권을 반대하는 시위가 한창 중이다..
유튜브 비디오를 보면 돌을 던지는 민간인을 향해 총을 쏜다.. 헉.
우리나라 5.18 민주화 운동때랑 비슷한 상황이랄까?

이타카 룸메 남친님이 이집트인이라서
어제 이집트 상황에 대한 자세한 설명을 들을 수가 있었다.
그 중 “어떻게 그런 상황에서 살 수가 있지?”란 생각이 든 부분은..

이집트의 40시간 직업 평균 봉급이 26달러 정도 된다고 한다.
그런데, 우유 한 갤런을 살려면 1달러란다. 일주일치 식량을 사면 쉽게 12~15달러가 되고, 한달 뼈빠지게 일해도 2주일은 굶어야 하는 지경이라, 이집트에 왠만한 사람들은 늘 일거리를 찾아다니고, 왠만한 사람은 낮일 밤일, 잡이 두개라고..

오늘 아침 미국 동부 시간으로 새벽 6시에 집회가 예정되어있었는데, 군중이 커지는 것을 두려워한 이집트에서는 유선, 무선 통신망을 모두 차단해버렸다. 그래서 어제 아담이, “지금 이집트가 오프라인이라서 구글 서버들이 트래픽을 다 우회하고 있어” 라고 하더군. 그리고 오늘 아침 알자지라 통신에서 이집트에 대해 얘기를 하면서 “이집트 (eGypt)” 가 현재 통신이 안되기에 “집트 (Gypt)”라 부르기로 해요! 다는 유머를 다 하더군.

큭큭…약간 웃겼다.


잠자리 그리고 Bole

Photo of a dragon fly taken with a macro lens

아담이 Bole라는 제목으로 이메일을 보냈다..
Bole는 나무의 줄기 수간이라는 단어인데, 첨부 파일을 보니 잠자리를 매크로로 찍은 사진이었다.

그래서 물어봤다..제목이랑 내용이랑 무슨 관계냐고..
그랬더니 아담 왈… “그거 볼레 자나..” “두 유 노우 보울레?”

Bole = 보울레 = 벌레

어째 한글 실력이 줄어드는 듯 하다..
쯧쯧..


Riverside Park

아담 그리고 나..
워드 프레스 기능들 시험 중… so far so good..


[Movie] Inside Job (Part 1)

코넬 씨네마에서는 시류에 편승하지는 않으면서, 색깔있는 영화를 주로 상영한다. 어제 7~9시에는 Inside Job이라는 다큐멘터리를 보았다. 미국 financial crisis에 관해 다룬 영화였는데, 영화도 유익하게 잘 보았지만, 영화가 끝나고 나서는 법대 교수님 (Robert Hockett)이 학생들과 함께 영화에 대해서 담화를 나누는 시간이 있었는데, 영화 만큼이나 값진 시간이었다.

영화에서는 2008년 경제 위기를 초래했던 일련의 사건들, 미국인들의 가치관, 그리고 경제 시스템이 어떻게 맞물려 있었는지 잘 설명하고 있었다. 다음은 내가 영화를 보면서 배운 내용이다. 사실 너무나 많은 내용을 2시간 영화로 설명하고 있었기에, 굵직굵직한것만 기억이 난다. 다시 가서 한번 더 볼 생각도 하고 있다. 하지만, 일단 단기 기억이 사라지기 전에 정리를 해보련다.


1. Deregulation
영화의 초반부에서는 레이건 정부 이래로 미국의 경제 시스템에 가해지는 정부 제제가 서서히 줄어들었음을 나열하였다. 아주 좋은 예가, 미국 은행들의 leverage한도 이다. Leverage란 은행이 예치금의 몇배에 해당되는 금액의 투자 상품을 살 수 있는지 나타내는 지표이다. 이 비율이 높을 수록 파산의 가능성은 높아지고, 만약 파산을 하게되면 정부 (Federal Reserve) 에서는 은행을 bail out해줘야할 의무가 있다. 이건 짚섬을 지고 화약고에 들어가는 격 아닌가? 도박을 하게 여건을 만들어 주면서, “망하면 내가 책임질께” 하는 격이라니..

2. Collateralized Debt Obligation (CDO)
2008년도 경제에 가장 큰 위기를 초래한 것은 이 Collateralized Debt Obligation 범주에 속하는 투자 상품들이다. 왜냐하면 이 투자 상품들은 가치가 별로 없는 C급 투자 상품들을 AAA급으로 둔갑시켜, 가난한 중소층의 퇴직금 및 연금들을 공중분해하는데 가장 큰 기여를 하였기 때문이다.

금융권에서 Collateral의 뜻은 “(융자를 위한) 담보; 저당물”이다. 그럼 Collateralized라는 의미는 “저당이 잡힌 빚”이다. 뭔 소리냐면, 만약 채무자가 빚을 값지 못할 경우, 저당을 팔면 되기에 투자자 입장에서는 금융 상품이 파산할 위험 부담이 적다는 의미이다. 사실 CDO자체는 좋은 시스템이다. 왜냐하면, 나중에 돈을 잘 벌 만한 학생들이 돈이 없이도 학교에 다닐 수 있게 (학생 대출) 도와주고, 돈이 없는 사람들에게도 집을 살 수 있게 도와주는 (집 담보 대출) 투자 상품이기 때문이다.

하지만 이와 같은 CDO들이 어떤 특정 집, 또는 특정 학생대출을 책임지지 않는다. 왜냐하면, 내가 산 CDO투자 상품과 물려 있는 담보 대출 상환이 원활히 이루어지지 않을 경우, 투자자들은 돈을 읽게 된다. 그래서, CDO 투자 상품들은 여러 담보 대출들을 묶어서 한번에 취급하고, 이 과정에서 투자자 위험 부담은 최소화된다.

근데, CDO 투자 상품에 묶여서 팔린 상품 중에 시한 폭탄이 있었다. 그는 바로 Subprime morgage라는 상품이다. 그리고 이 시한 폭탄이 CDO투자 상품에 묶일 수이 있는 환경을 만들어 준 것은 미국 정부의 Deregulation일환에서 일어난 일이다.

일단 Subprime morgage가 무엇인가? 일단 prime 이 뭔지부터 설명한다. 미국 Federal reserve가 일반 은행에 적용하는 이자율을 prime이라 한다. 일반 은행에서는 prime보다 높은 가격에 돈을 대출해줘야 돈을 벌 수가 있다. 그런데, Subprime은 처음 몇년간 이 prime이자율보다 낮은 가격으로 돈을 대출해준다. 이게 왜 가능할까? 그 이유는 담보의 가격이 오를 것이라는 가정이 있기 때문에 가능한 것이다. 지난 15년 이상 미국 집값은 매해 꾸준히 올랐다. 채무자가 의무를 이행하지 못하더라도, 은행에서는 담보인 집을 팔면, 매해 주택가격 증가분에 해당하는 이율을 낼 수 있단 얘기다. (사실 간단하게 설명을 해서 그렇지, 매우 복잡한 시스템이다. 내가 과연 제대로 이해하고 있는지도 알 수가 없기에 기회가 나면 다음에 더 설명을 하련다). 주택시장은 과열이 되어, down payment를 하나도 내지 않고서도 subprime morgage로 집을 살 수 있는 지경이 되기 시작하였고, 주택 가격 증가분이 은행들의 기대치에 달하지 못하면서부터, subprime morgage는 적자를 내는 시스템이 되기 시작하였다. 그래서 가장 먼저 무너진 회사가, house morgage상품을 주로 담당했던, Freddie Mac, Fannie Mae (2008년 9월) 이다.

이 여파로 subprime morgage 상품이 들어 있었던 CDO들은 부도가 나기 시작했다. 이 CDO를 가장 많이 만들어서, 돈을 가장 많이 번 회사가 골드만 삭스이다. 그래서 Subprime morgage들이 제대로 돈을 벌어들이지 못했을 때, 그래서 Subprime morgage들이 섞인 CDO들이 투자 가치가 없어지기 시작했을때, 곤두박질친 주식이 골드만 삭스 주식이었던 것이다.

3. Credit Default Swap (CDS)
골드만 삭스가 몰락하기 전에 무너진 중요한 회사가 하나 더 있다. 바로 American Interation Group (AIG)이다. AIG는 보험회사이다. AIG는 금융 상품을 보험하는 상품이 많았는데, 그 중 가장 문제가 되었던 것은 CDO들을 보증하고 있던 CDS이다. 이 CDS가 불이 난 화약고에 기름을 끼얹는 역할을 하였다.

CDO들이 부도가 나기 시작하였을 때, AIG에서 부도를 왜 막지 못했을까? 그 이유는 여러가지지만, 가장 큰 이유는 CDO를 보증하고 있는 CDS가 여러개였다는데 있다. 이게 무슨 소리일까? 만약 10개의 CDS상품이 적용되는 CDO가 한개 부도났을 경우, AIG에서 감당해야하는 부채는 실제 부채의 10배인 것이다. 그리고 골드만 삭스, 그리고 메릴린치 등 투자 은행에서는 투자의 목적으로, 그리고 CDO의 리스크를 줄이기 위해 여러개의 CDS를 하나의 CDO에 사들어 놓았다. 근데, AIG가 더 이상 부채를 감당하지 못하고 파산의 지경에 이를 것이라고는 생각도 못한 것이다.


그렇다면, 이 지경이 되기까지 미국 정부는 무었을 했을까? 클린턴 정부는 어떤 불씨를 심어놨으며, 부시 정부는 뭘 했을까? 왜 오바마 정부가 들어서고서도 아무런 진척이 없는 걸까? 영화에서 선정적으로 다루어, 오해를 일으키고 있는 내용은 어떤 것인가? 코넬 법대 교수님은 이 일련의 사태를 어떻게 해석하셨을까? 그린스펀, 버냉키, 서머스 등등은 뭘 했으며, IMF 그리고 유럽 정부에서는 어떤 경고가 있었을까?

등등을 쓰고 싶으나, 머리에 쥐가 난다.. Part 2에서 써야지..

결론은, 볼만한 영화였다.


How to write a ACM sigchi rebuttal

I originally wanted to post this during the SIGCHI rebuttal period. However, I was afraid that it may hurt the acceptance rate of my paper somehow. (Maybe by revealing my identity to the external reviewers? I don’t know. Anything is possible. No?) Hence, I decided to write this immediately after the notification, while everything is still hot in my head.  Maybe students that have to write a rebuttal for CHI2012 may find my post useful.

First, I will start by my opinion on why it is difficult to write a convincing rebuttal.

If 90% of writing a paper requires knowing how to explain a research idea and 10% knowing how to convince another researcher, writing a rebuttal requires 10% of the former and 90% of the latter. As a junior researcher (like myself, a graduate student), the only senior researcher you talk to in a daily basis is your advisor.  Yet, your advisor is only one sample point among the pool of senior researchers. How on earth would you know how to convince another senior researcher when you do not even know how to initiate a serious conversation with them?

It is always difficult to take criticism. This is especially the case for people like us Ph.D. students who always strive to produce results that are flawless. We seldom hear that our work is a crap in our face. Additionally, the criticism that we have to take in the review seems unjust especially when you believe that the person who’s making the criticism spent maybe a day or two reading a document that you spent endless nights editing over and over again for several months.  Some reviewers are actually nasty too. Although it is written in fancy and erudite terms, sometimes the reason that they are rejecting your paper is simply because, “you did not do a good job in impressing me” or “I do not buy your research story”. How would you possibly stay sane when you read these comments?

Despite, many reasons to yell at your reviewers and say, “you are full of s**t~!!”. We should not even express this in any indirect way while writing our rebuttal. In the past, I always had to discard the very first draft that I produced after reading the harsh reviews. My rebuttal was bitter, smirking, cynical and mean. This was not obvious until I slept at least two days crying over it and returned to my calm and reasonable self.

This year, due to my post (in my Korean blog) about my experience in writing a CHI rebuttal in the past years, I’ve been asked by several junior students (outside my institute) to help out in writing their rebuttal. While doing so, there are several tips that I repeated. Here are some of them.

[Understanding and analyzing the review]
Read your reviews with another coauthor and have an in-depth discussion. It is important to address the most important issues first and address only the problems that reviewers raise. Sometimes, I realize that I misunderstood what the reviewer meant and was addressing something that was totally unnecessary. Sometimes, I structured my arguments in the wrong order: order of least importance to most importance.  Many authors actually make these mistakes during the writing process, not because they are careless, but because the reviews are somewhat encrypted. Not all of them are kind enough to tell us “A is unconvincing and A’ is my opinion. B and C are what I do not understand but authors should only address B because C is not as important”. It comes more like this, “A is weird, B is weird, C is weird”. Usually, meta-reviewer tries help us by decrypting the dialect of the external reviewers so that the authors are not at a loss. However, not all meta-reviewer are nice either. For this reason, I always talk with my advisor or one of my coauthors for 2~3 hours about the reviews before writing anything. This usually helps a lot.

[Writing process]
Agree with your reviewers. Last year, one of the rebuttal of the paper that I reviewed basically stated that “R1 (myself) is wrong because so and so, and our paper is awesome”. This rebuttal didn’t acknowledge some of the important problems that I pointed out and tried to challenge my judgement. I was offended and became more strict in finding faults of the paper during the discussion period. This is the last thing that the authors want. Making an enemy among the reviewers. To make an ally, you have to tell them how useful their feedbacks are and you have to sincerely mean it too.

Specify how the camera ready version will be reflected based on the reviewer’s request. Often, there are rebuttals that just say, “I understand R2’s point”. This is only half-baked response. The goal of the rebuttal is to demonstrate how the camera ready version will be changed according to the issues raised. Hence, the response should be more specific and go even one step further. Like this:  “the question A is raised by R2 because we only explained B in section C when it is also needed in section D. In the camera ready version we will clarify B in section D”

Do not say that the draft will be improved with a major change. I have seen several authors that say in their rebuttal “After the submission we did A,B, and C which addresses all of R1,R2, R3 questions which will be updated in the final draft”. This approach is very bad. First, you are admitting that current draft has many issues. Second, during the PC meeting, papers are discussed “as is”. If it is concluded in the PC meeting that the paper requires major revision, PC members advise that it should be submitted to a future venue. Better approach is to figure out what reviewers misunderstood. Explain why there was a miscommunication and offer ways for reviewers to solve those misunderstandings. Point to a paragraph or a figure in the paper. If needed, direct them to a reference that is not cited in your paper. This is what a rebuttal is for; to clarify.

[Formatting and Style]
Although 5000 characters limit may seem insufficient to explain everything, do not hesitate to allocate some of those characters in white spaces and phrases such as (in response to R1, as mentioned by R2, in our RELATED WORK section, in p8~9). At a glance, they want to see which major raised points have been addressed and which part of the paper they should read again. Sometimes, I use the web browser search tool (namely Ctrl+F) to locate my reviewer id (RX) in the rebuttal and read the accompanying paragraph more carefully to make sure that I didn’t miss anything.

Last but not least, write short and direct sentences. Any sentence that you write to explain in your rebuttal have 50/50 chance of helping your paper and hurting your paper. The longer and indirect a sentence, the higher chance of mis-interpretation. On top of that, reviewers have very short attention span. If sentence become convoluted, they will read what they think the sentence is saying as opposed to what the sentence is actually saying.

The biggest question behind all this is, “Does reviewers actually change their score after reading a rebuttal?”.

And the answer is “YES”~!!. Among the 7 papers that I reviewed this year, I increased the score by 0.5 in one paper because I was happy to learn something that I didn’t know from the rebuttal. Among my 4 papers (2 in previous years and 2 in current year) that have been accepted, 3 paper scores actually increased (by +0.4, +0.1, +0.4) after the rebuttal period.

Although it is painful and tedious process to write a good rebuttal, it is very rewarding once you DO write a good one.


Cornell Hockey Games

This month, I attended two hockey games against other IVY league school, Dartmouth and Princeton.

The game against Dartmouth (6th) was with Adam and Hronn. Adam made an effort to come to Ithaca after his submission to WWW. Originally Hronn managed to get two hockey tickets from a CS faculty member. As the Gilmores have three season tickets, I was hoping that Adam get to come along even if we have to sit in different section. On the day of the Hockey game, Jim proposed a brilliant idea of exchanging 2 tickets with the 3 tickets that they have so that our couple and Hronn can enjoy the game at their seat and two Gilmores watching the game at the CS faculty seats. Between 1st and 2nd period, Rhonda came over to our seat telling us how impressed she was with Jim’s “intellectual girth” of the day. =)

The game against Dartmouth was relatively relaxing. I already researched before the game that they are ranked the lowest among IVY league teams. Not to my surprise, we won with 5-to-1. Because it was obvious that we will win, I was able to pay attention other aspect of the game. Before, I was occupied in keep track of which player it was that crashed against the wall and where the puck went. (Visually following the puck requires quite a concentration. It feels almost like one of those magic tricks where you have to visually track which one of the three cups are hiding a ball.) I noticed that some hand signs that the referees made for some penalty was not self-explanatory. One time, Cornell pulled out our goalie even when our score was already 4 points or so. One of the Cornell players were knocked out on the ice for about 5 minutes after tripping over another Dartmouth player but I couldn’t figure out what kind of penalty the Dartmouth player got. That night, Adam and I sat across each other on my living room sofa with out legs braided one after another looking up penalty rules on Youtube. (http://en.wikipedia.org/wiki/Penalty_%28ice_hockey%29).

This week, Hronn rushed to my office shouting “I have tickets for the hockey game!”. It was against Princeton which I had very bad feelings against. Last spring, they beat us to 1-to-2 on my very first hockey game experience. It was quite a tragic how we lost. On the very last 1 minute on the last period, they pulled out the goalie to fight with 6 offensive players and scored a goal on the 38 seconds before the end of the game. The game went overtime for sudden death and the result wasn’t pretty. Bottom line, I was very excited to be in the ice rink to see the game hoping to see a revenge.

When Hronn showed me the tickets for the Princeton game, I was slightly puzzled. One was on row 14 and the other was in row 2 of section B. She replied, “We will be fine, it’s in the student section and it’s going to be crazy anyways. We will be able to swap seats or squeeze you in to row 2.” And yes, she was right with both points. We were both able to enjoy the game in row 2 which was spectacular. At the same time, the entire section was totally out of control.

Student section cheers during the ENTIRE game. Everybody screams their lungs out that I often saw droplets of spittle clash against the plastic wall in front of us. One guy behind us was eating pop corn. From time to time, the pop corn will fly and hit against the plastic wall too. Hronn and I felt like being baptized by the Cornell undergrads’ spitting from behind. We told each other that next time we will remember to wear a cap and laundry clothes. Furthermore, some undergrads were clearly drinking alcohol during the game. When the student section shouted “Let’s go Red”, the smell of alcohol fumes from behind made us quite dizzy.

Nevertheless, I learned so many cheers (http://www.elynah.com/?cheers), some of which were very funny, some of which were very brutal and atrocious. Whenever our player scores a goal, the entire student section said “Sieve, Sieve, Sieve, Sieve, You SUCK!” and then it will be followed by “It’s all your fault~, It’s all your fault”. When the other team goalie manage to block a puck, the students shout “Lucky sieve, Lucky sieve~”. This was all cute and funny. However, whenever a period ended and the Princeton coach was leaving the bench, the entire student shouted “Bald, Bald, Bald x10” which I thought was too insulting.

When 2 minutes were left, Hronn and I both remembered to pull out our key chain and jingle. I told Hronn, “Thank you for sharing your ticket with me~!”. Hronn replied, “Thanks to you that this time, I know that key chain jingle in the third period means it’s the end of the game!”


Google search engine – Hyunyoung Song

My personal web page http://www.cs.umd.edu/~hsong inherits the high page rank due to the high page range of http://www.cs.umd.edu/ host site. Hence, when “Hyunyoung” or “Hyunyoung Song” is entered as a keyword, my webpage is the first item on the search result.

Another competing identity with hyunyoung keyword is a Korean singer named “Hyunyoung” who’s known for her song “Nuna’s dream” (Nuna is a generic term for “older sister”) Usually, google is very good at distinguishing whether a keyword phrase is entered to look at one of my publications, or whether the keyword is designed to search for the Korean singer. For example, if it is “Maryland Hyunyoung”, Google directs my webpage. If it is “Hyunyoung singer”, Google directs the user to the singer’s webpage.

Today, as I was looking at my visitor log and some searched keywords, I found a phrase that is very obvious that was intended to find the Korean singer but the google engine thought that my webpage was more relevant.

The phrase was: “Hyunyoung Nuna Song”

Hahahaha