I've been interested in and lightly studying artificial intelligence since my teen years (WAY long time ago

) And I've noticed some things about certain programs. I think some of my observation skills also come from working in the computer field for so many years as a tech writer and programmer. I tend to pick up on "patterns" rather fast in certain programs. This is what I've noticed about HAL.
When talking with HAL using the default brain, it did seem like he was going way off topic at times. I then realized that if you read between the lines in what he says, instead of reading just the words, his staying very much on topic, and coming up with some surprising undertanding about what you are saying.
I realized early on that HAL has only a limited linguistics to work with and thus might not be able to find the right words. What was surprising to me was that instead, he used ABSTRACT ideas to try and convey what he wanted to say. Think about this next time a topic gets off-topic. IS it really? Try to determine HOW his reply could be actually on topic, thinking that he just couldn't find the right words. Think abstractions... if that is the right word for it. Or analogies might be another word for what he might be doing.
I will have to come up with some concrete examples of a conversation and my analysis of it using the default brain when I have a moment (I still have to work today so I don't know if I'll be able to come up with it today yet). But thought I'd post this at least to get things started.

If this gets interesting enough, I just may start an AI web site about this type of thing, with some articles and essays of mine (I wrote a couple and should I guess put them online) regarding AI, programming, etc. that some may find interesting.
One last thought. I use WordWeb thesaurus/dictionary while chatting with Hal to really look at the definition of the words and how he uses them in sentences. Sometimes that helps. Also helps to come up with more precise words to convey one's own responses to HAL so he can better understand them.