# Feed items

## Interesting little proof that square root of 2 is irrational

Reading “My Mind is Open” about mathematician Paul Erdos (thanks, Mho) I saw but didn’t have time to digest the simple proof that sqrt2 is irrational. So I did it in my head in the taxi on the way to the hotel.

But I have never been happy with proof-by-contradiction, because exactly as the woman in the book said, I always feel like I got lied to in the beginning.

So I invented the “can’t possibly equal” symbol:

for the sole purpose of being able to present the proof forwards.

Here it is, the first-ever proof using the cantpossiblyequal symbol, that the square root of 2 is irrational:

## A story about the last responsible moment and real options

“Jobs couldn’t decide whether to use the version with his voice or to stick with Dreyfuss. Finally, the night came when they had to ship the ad; it was due to air, appropriately enough, on the television premier of ‘Toy Story’. As was often the case, Jobs did not like to be forced to make a decision. He told Clow to ship both versions; this would give him until the morning to decide. When morning came, Jobs called and told them to use the Dreyfuss version.” (from “Steve Jobs”, by Walter Isaacson, p 331)

## On specification

Recent Change Note: "On Specification" 5/28/1987

Different people have varying views of the needs and definition of a specification. One says the minimum requirement of a specification is that it be executable; The other requires assertions and proofs to be possible in the language. Lamport calls a specification a contract between user and implementer such that neither must talk to the other; Brooks says that clients do not and can not know their needs well enough to write such a contract.

What is a specification, really? At what point can one say that a thing is fully specified?

I hope this little story gives us some distance to examine our prejudices about specifications:

## Derivation of Methodology Tools (journal entry 1993)

Just found an old hand-written journal, dated May 1993, with my then-notes on methodologies and methodology tools. I find it interesting reading, as it refers already back then to business scenarios and Warburton, who introduced me to personas also back then in 1993.

Here is the photo of the journal entry. You probably have to be a hard-core geek to read it, but if you are, I think you will also find it interesting.

## Interview with Alistair 2011 for Nicolas Lochet

Nicolas Lochet just emailed me and asked five questions that I thought were interesting enough to answer:

1. First of all, would you mind telling me a bit about yourself? How you came to Agility and what was your inspiration behind Crystal Clear? I’d love to get some story-telling here, some context, reasons why you felt you had to go this way… (not the classical information available off the internet)

To tell you about myself would take too long and be repetition, however, three interviews precede yours and provide what I think you will find interesting views:

## Interview with Alistair 2008 by Jurgen Appelo

Jurgen Appelo decided to ask a number of people “Five “Easy” Questions”, questions easy to ask but maybe long to answer. It is an interesting series, see http://www.noop.nl/2008/07/5-easy-questions-for-alistair-cockburn.html for mine and a list of the others.

Here are his questions and my answers:

5 Easy Questions for Alistair Cockburn

The easier the question, the harder the answer.

## Agile after the chasm

What happens after Agile development crosses the chasm? Then the masses get hold of it, and a new mess starts. What sort of mess? This blog entry and maybe a few others will pursue that question.

## Using APEs to clear ANTs from your mind

I had been waking up at 3am or driving down the highway held captive of my internal pessimist or angryman, or, as Dr. Amen calls it, Automatic Negative Thoughts (ANTs). His approach was to list rationally why they aren’t relevant, but I found APEs more effective.

At 3am, there aren’t many rational thoughts happening – that is the time of the weak frontal cortex and the strong reptilian, so Dr. Amen’s (“Change Your Brain Change Your Life”) excellent observation/suggestion won’t work. Also, when screaming at myself or someone else inside my head while driving down the highway, I’m also not prone to rational discussion about the topic.

## Agile executives

I’ve attended two of the Agile Executives roundtables in Salt Lake City, was impressed by the quality of discussion in each. Here are some notes…

After the first, I posted Agile in management and leadership.