The farthest paths that have been explored, we call the frontier.

It starts off by initializing the frontier to be the path consisting of only the initial states, and then it goes into a loop in which it first checks to see do we still have anything left in the frontier?

And we pop that empty path off.

So let's write down those three components.

Which we have come to regard as natural.

Instead, we just continue in the normal way and choose the node on the front tier which has the lowest value.

I expected it.

This one, this one, and this one.

The answer is this one. Two twenty is less than 229 or 239.

It's final because once we reach it, it's limitless.

The piece that he was working on, RSS, was a tool that you can use to get summaries of things that are going on on other web pages.

They drove a tunnel through the hill.

I want to spend most of my time on this part of the world.

The answer is that we're not done yet, because the algorithm works by doing the goal test, when we take a path off the front tier, not when we put a path on the front tier.

True, we have added a path that ends in Bucharest, but the goal test isn't applied when we add a path to the frontier.

So 140 is the lowest.

These are all points on you as a hunter gatherer, on your production possibilities frontier.

And only a few years later in 1986

And that's the cheapest, so this one gets expanded.

A final frontier begins in this hall.

Now Tree Search represents a whole family of algorithms, and where you get the family resemblance is that they're all looking at the frontier, copying items off and and looking to see if their goal tests, but where you get the difference is right here, in the choice of how you're going to expand the next item on the frontier, which path do we look at first, and we'll go through different sets of algorithms that make different choices for which path to look at first.

Isaiah Berlin put it this way

Again, we don't stop here just because we put a path onto the front tier, we put it there, we don't apply the goal test next, but, now we go back to the front tier, and it turns out that this 418 is the lowest cost path on the front tier.

(Applause)

Not through E.

Oh, Ha Ni, Oh Ha Ni!

If it comes up, some of them will be submerged.

Through the girl?

Through the family.

length 0, starting in the start state, and that's the only path in the frontier so it's the shortest one so we pick it, and then we expand it, and we add in all the paths that result from applying all the possible actions.

Policemen cleared the way to let cars pass.

I don't communicate well through a shroud.

So I hushed my voice.

And bring him in through the southeast service entrance.

I talk to my analyst.

Here is our tradition

So how do we recover from that, ladies and gentlemen?

I wish I could show you my Yemen.

Jam its signal!

Now, here's another representation of the search space and what's happening is as we start to explore the state, we keep track of the frontier, which is the set of states that are at the end of the paths that we haven't explored yet, and behind that frontier is the set of explored states, and ahead of the frontier is the unexplored states.

Out of the way. Out of the way, everybody.

Hurry!

Excuse me.

Send him in.

Let me through! Wikus!