daniel bigham.ca

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Deriving facts using rules
September 11, 2008

The next area of research I'd like to explore is that of deriving facts about the world using rules.

Rules consist of two parts:

1.	A list of conditions that must be met for the rule to apply.

2.	A conclusion or implication, which says something is true if all of the conditions are true.

What makes rules useful is that any part of a condition can left undefined and represented by a variable, which is then used in another condition or the conclusion.

For example:

Conditions:

1.	A person's first name is $1

2.	A person's last name is $2

Conclusion:

The person's full name is '$1 $2'.

This can notated as follows:

rule:
  $1 is_a person
  $1.first_name = $2
  $1.last_name = $3
  -> $1.full_name = '$1 $2'

Some more examples:

rule:
$1 on_top_of $2
-> ! $2 on_top_of $1

rule:
  $1 is_a person
  $1 born_in Canada
  -> $1 is_a Canadian

rule:
  $1 is_a person
  $2 is_a person
  $1.birth_date > $2.birth_date
  $1 older_than $2

etc.

Rules come in very handy when trying to answer questions. For instance, consider the following story:

My first name is Daniel
My last name is Bigham
What is my full name?

The AI wouldn't know the value of speaker.full_name implicitly because it was never told its value. But it can derive that value given what it knows.

There are three primary cases where rules can be applied:

When the AI is told something, it can search for rules for which what it was told matches a condition of the rule. Finding these rules, it can then check whether it has all the necessary information to indicate that the conclusion is true, and if it is, it can update its brain state with the derived information in addition to what it was specifically told.

In the example above, an AI could apply speaker.full_name = 'Daniel Bigham' as soon as the second statement was made, long before the question was even posed.

2.	When the AI is asked something. In other words, when asked for the speaker's full name, the AI could search for rules whose conclusions match the information it is looking for, and then determine whether all of the conditions are met.

In a sort of recursive scenario, checking to see whether a rule can be applied may involve using other values that are not explictly known. This can trigger a second rule search to see whether that value can be derived, and so on. What you get is a kind of search tree. Obviously you wouldn't want a scenario where the AI goes off and spends 5 minutes exploring a huge search tree, so the depth to which it explores would need to be set to a reasonable number.

Rugby
September 10, 2008

I've never really been all that interested in Rugby: A strange looking sport, somewhat similar to football, that is mostly played outside of North America.

Today as I was biking back from work, I stopped and watched the Warrior's womens team play. It looked so fun! You have the tackle aspect of football, which I love, but it's nonstop action. It makes football look boring in the same way that baseball is boring: So much idle time waiting for the next play.

Another thing that makes Rugby interesting is all of the lateraling, kicking, and various ball movements. It's such a varied, action-filled game!

And then, it's also fun watching girls tackle each other... I mean...

Random thought: What about using a pen instead of a mouse?
September 10, 2008

It occurred to me today: What device have people historically used to provide them with a high degree of pointing accuracy? A pencil, or a pen. And that's what a mouse does: It gives a person a high degree of pointing accuracy.

Given that a pen is something people learn to use in school (even previous generations are great at it), I'm surprised that this hasn't been used more.

Now, pen interfaces already exist... artists use them for drawing on the computer, etc. But if I'm not mistaken, you have to also hold the pen up to a special surface. I wonder what this technology might be like if you didn't have to hold the pen up to a special surface, and it still worked if then pen came a little off whatever surface you held it against.

Does it afford more or less accuracy than a mouse? What would it be like using a computer with this device for clicking on icons, dragging windows, etc.

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