Older blog entries for chalst (starting at number 189)

22 Apr 2008 (updated 22 Apr 2008 at 12:36 UTC) »
Some trust-metric references
All the references listed below link to PDFs, with my comments in italics.
  • Weeks, 2001. Understanding Trust Management Systems. Crucial paper for understanding much recent work on trust-metrics. Presents framework, motivates it with examples, and shows PKI can be modelled using it.
  • Carbone, Nielsen and Sassone, 2003. A Formal Model for Trust in Dynamic Networks.. Proposes a simple domain- theoretic formalisation of what a model of trust is that provides the basis for some significant later work.
  • Twigg and Dimmock, 2003. Attack-Resistance of Computational Trust Models. Synthetic exposition of several trust-metrics that have some degree of attack resistance. Good exposition of Raph's metric, sgives alternate proof of attack resistance by order-theoretic reasoning.
  • Moreton and Twigg, 2003. Trading in Trust, Tokens, and Stamps. Proposes system for adding trust trading to trust-metrics by stamps, and argues for advantages of this system. Interesting for Advogato: could provide a more principled means of bringing in new members than just rejigging weights.
  • Ziegler and Lausen, 2005. Propagation Models for Trust and Distrust in Social Networks. Motivates criteria for success of trust-metrics when applied to social networks, including attack resistance. Proposes a new algorithm, which they call Appleseed and which is based on the spreading activation technique, which they compare to Raph's version. This work is based in part on Ziegler's PhD thesis, Towards Decentralized Recommender Systems.
I'm curious as to the origin of Raph's talk of "good", "bad", and "confused" nodes. Is it his novel usage, or did he get it from elsewhere?

I'm amused also to read references sections that cite Raph's abandoned trust -metrics thesis as if it was a successfully defended one. Folks who run into the thesis he did write will no doubt conclude he is one of the select few who wrote two PhDs concurrently...

Food prices
I've been thinking and worrying about food prices more and more over the last four weeks, and I see that skvidal shares my worries.

In fact, he doesn't worry enough! When he talks of food prices "spiking", there's more to the story. The S&P-GSCI agricultural commodity price index, which is the main aggregate food price index, has shown a nearly three fold increase from Jan 2005 until the beginning of this year. Given the terrible access to credit poor farmers face, this is likely to mean that food prices, already difficult for many to afford, will get higher as the year progresses. If there is nothing done to relieve the situation, it will spell immense suffering and political instability in much of the world.

It's a scary picture, and if it isn't ignored by the world media, not enough attention is drawn to just how serious this all is. It's pretty damn clear that the story matters more than the bloody farce in Iraq (which has contributed to it by pushing up oil prices), and it is more important than the financial turmoil shaking the world right now (though that will make it harder to do anything to help).

Can we do anything to help? Skvidal has suggestions: I wonder if growing food is an option for me? lkcl's article Singularity of computing, might have something to do with food price stability in the future, though I don't suppose this kind of thinking about technology can help with this year's crisis.

What should I believe?
On Friday, the Financial Times tells me how Germans feel Schadenfreude towards Anglophone countries, because the economic pain those countries are suffering will pass them by, because of the fairly healthy state of the German finance system, growing internal demand, and because the peculiar makeup of Germany's export markets puts it in a good position to weather the coming global economic downturn.

On Saturday the Financial Times tells me how Germany is headed for a nasty fall, because domestic demand is faltering, and its export-centric economy is particularly vulnerable to the coming global economic downturn.

26 Mar 2008 (updated 26 Mar 2008 at 12:22 UTC) »
Advogato certifications again
I've just certed henrique, despite his not having a link to anything identifying him and saying what free software projects he is involved in.

This is generally against my policy, but the Henrique Romano involved in Django and some other python projects doesn't seem to have a home page, and he does post contentful diary entries here, so...

As a general point for newcomers seeking certs, I, and I think others, pay more attention to diary entries than account creation, and to some extent I trust local diary content more than RSS feeds.

19 Mar 2008 (updated 20 Mar 2008 at 10:50 UTC) »
International money transfer tips
bagder wrote: Receiving money from abroad is not easy.

And he is quite right, especially when he is in the US. But some things might help:

  1. Wire transfers for some banks become much cheaper and involve dramatically less bureaucracy if you set up a wire transfer authority.
  2. Paypal is convenient, but its cut is outrageous: a few years ago I figured that they would take 8% on a $14,000 transfer from Germany that I was planning; that's $1,120. I used XEtrade instead, who were very cheap and not much hassle.
  3. Negotiating cheques between banking systems is a major nuisance, but your best bet is probably to use an independent money broker. It's mostly a problem the other way around though: in my experience only Americans ever think that settling accounts by sending cheques to addresses abroad is a good idea...
  4. You can sort of make IBAN transfers to countries outside of the IBAN network by using an intermediary (usually a retail bank). I tried this with a money transfer to Brazil where I sent the money to the IBAN account of the Brazilian intermediary's account in the Netherlands, with the details to the recipient's Brazilian account in the "reason for transfer" field. It took months before the money finally arrived...
I've not seen a euro denominated cheque yet, though I gather the French and the Irish still write them.
Linked to without comment
  1. Arnold Zwicky writes on To Henry Fowler on the occasion of his 150th birthday;
  2. Mark Jason Dominus on Drawing lines.
FizzBuzz
Zaitcev wrote: English kids who play this game in kindergarten are freaking geniuses. The only sensible plan seems to be to keep two counters, which is actually quite challenging.

It seems tome that a better strategy would be to count in groups of 15 at a time, and memorise where the Fizzes, Buzzes and FizzBuzzes occur. It's feasible to make a rhythm out of it, to keep track of where you are. I think I could teach my 4 year-old to count to such a rhythm, though her grasp of number greater than 12 is a bit shaky at present (she starts making up the sequence, repetitions and all, when she gets unsure), so maybe her rendition wouldn't be so impressive.

If I were to try to code this in 2mins, I'd probably choose perl, and choose from an array of 15 format strings. Maybe I try that, see how long it takes.

The rather harder version of the puzzle if that you call "Fizz" if either the number is divisble by, or whose decimal expansion contains, 3, likewise for Buzz, FizzBuzz.

13 Dec 2007 (updated 13 Dec 2007 at 13:49 UTC) »
Lazyweb
Two questions:
  1. What's the best way to mount an HFS+ partition on Linux?
  2. Has anyone any tools that support (however partially) mounting volumes captured in .dmg files? baghira.sourceforge.net says it can be done, but I haven't got these instructions to work, probably because my /sbin/mount barfs on "-t hfs"...

While I'm talking OSX
Rixstep occasionally comes up with the goods. Eg.

OK then - now here's the real no brainer: have you ever seen Apple dump a .DS_Store in one of their Cocoa applications?

Think about it.

12 Dec 2007 (updated 13 Dec 2007 at 13:17 UTC) »
Recentlog
davidw wrote: Economics is generally a pretty good way of thinking about problems like that - one of the best there is. But it's certainly a system that is far from perfect, and Munger points out some of its defects in an effective way, without going overboard and trashing the whole discipline, as some do.
Of course, one can go overboard and trash nearly the whole of the subject in a disciplined and scholarly way. Indeeed, the results of this appeal to me, which is why Robert Vienneau's Thoughts on Economics is one of my favourite weblogs.

bagder wrote of Fred Brooks' classic: Large portions of it feels of the age and there’s a lot of talk about Fortran, System/360 and PL-1 as if we should know about them. We should know about these languages and systems, if we want to really understand how the language design and software engineering issues that we face today in modern languages came about. Checking out LtU's history department can help you make inroads into this, especially the stories with "HOPL" in them.

12 Dec 2007 (updated 12 Dec 2007 at 10:14 UTC) »
Move Along Now, Nothing To See Here
This was a duplicate post, that I think arises from some way in which advogato handles previews.

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