Feb 22, 2010

In Praise of Bibliographies

One of the best things about books are their bibliographies.  Sometimes a book's bibliography is worth more than the book itself.  If it is any good, the bibliography arms you with a map, or a mini-library, to other treasures about the subject you are reading about.   

When you are reading the very first book you have read about a subject, the bibliography is often a map to a new world. If it's a good bibliography, it leads you to treasure. But sometimes it can lead you to a rubbish pile. 

I always skim through the bibliographies of each book I read, marking down titles that may interest me next. 

It’s still vivid in my mind the occasion when I first came across Patrick Henry Winston’s “Lisp”. I remember exactly where I was.  I found a copy at our school library. I was in university, somewhat new to programming, but already infected by an intense interest in computer science, a subject I only had recently discovered. 

I had already read perhaps a dozen Pascal and Fortran books before picking up “Lisp”, but Winston’s was the most wonderfully strange computer programming book I had come across then (and still since). 

First was the very strange programming language (Lisp was not like normal procedural languages).  Then the domain was very new to me (it was the first book I read about Artificial Intelligence).  But it was also because Winston had a quirky writing style.  Looking back later, and understanding his academic interest in how humans learn, I’m sure this style was deliberately designed.

His book imprinted in my mind the names of dozens of computer scientists in the AI field. Names like Marvin Minsky, Douglas Lenat, Elaine Rich, and others whose very unusual sounding names (to me back then) felt like they were not normal humans, but members of a different breed, a strange breed, an alien breed. I swore to read all of them.   

Not all bibliographies are good (and by bibliography I include ‘References’). But, off the top of my head, authors who are great at compiling bibliographies include Andrew S. Tanenbaum, C. J. Date, Jeffrey D. Ullman, Douglas Comer.

Sometimes I forget how I learned about a book. I estimate that of all the books I’ve read or intend to read, the vast majority were inspired from a bibliography of some book I read.

So I thought it might be a fun exercise to list down some key books that have influenced me, write down their bibliographies (I’ll limit it to books only), and see how they are connected.

This is a tedious exercise so it will happen slowly, and when time permits.

Nov 16, 2009

Example of a Decision Tree

A simple example of using a decision tree to help us with decision-making.

A couple renting an apartment and is wondering whether they should sign a 1-year contract on the rent.  If they sign a contract, their rent is guaranteed not to increase during the 1-year period. If they don’t sign a contract, their rent will increase by about $20 after 6 months.

This seems like a simple decision.  But there is a drawback to signing the contract. If the couple decides to terminate the contract before the end of 1 year, they are liable to pay up to 25 weeks worth of rent to the landlord, unless the landlord is able to get someone else to rent the place earlier. 

The couple intends to buy their own home if the right opportunity comes, so there is a chance that they would need to terminate any contract they sign.

Supposing the initial rent is $900 per month, what is the couple’s best option?

Let us choose the simplest situation first.  Let’s assume there is zero chance that the couple will terminate the contract.  So the decision tree looks like this:

DecisionTree01

The tree says that the option to sign a lease contract will result in a total 1-year rent of $10,800 ($900 * 12 months), while not signing a lease contract will result in a total 1-year rent of $11,800 ($900 * 6 months + $900 * 1.2 * 6 months).

But what happens if the couple finds their dream house and moves out of the house after 8 months?

Nov 12, 2009

The Essence of Risk Management

All of man’s activities is fraught with uncertainty and risk.  When he undertakes something, he faces uncertainty and risk and loss.  Even when he does not undertake anything new, but simply goes on with life as normal, he still faces uncertainty and risk and loss.

Therein lies the essence of risk management, to which man runs to, to seek an answer to his question: in the face of this uncertainty, what should we do?