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

So let's write down those three components.

I expected it.

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

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

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?

This one, this one, and this one.

Which we have come to regard as natural.

And we pop that empty path off.

So 140 is the lowest.

And only a few years later in 1986

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

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

A final frontier begins in this hall.

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.

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.

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.

Now it could be called shortest first search because what it does is always choose of the frontier one of the paths that hadn't been considered yet that's the shortest possible.

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.

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.

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

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.

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

missiles firing up

Male narrator

Aaron was one of the most prominent people in a community of people who helped lead organizing around social justice issues at the federal level in this country.

And I believe that if you are a beneficiary of that civilization it is your duty too.

If we go ahead and make a choice of one of the paths on the frontier and remove that path from the frontier, we find the state which is at the end of the path, and if that state's a go then we're done.

One of the things that we did with the Ansari X PRlZE was take the challenge on that risk is OK, you know.

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.

And so at last mankind began the conquest and colonization of deep space.

And this time the lands that we see are truly unpopulated, they are waiting for the gift of life.

So, the distance that has historically separated our dreams from reality has shrunk to a point so near that for all intents and purposes we're fully immersed within it.

Now we reach Bucharest, which is the goal, and the h value is going to be 0 because we're at the goal, and the g value works out to 418.

And that's why, now, the new breakthroughs, the new frontiers in terms of oil extraction are scrambling about in Alberta, or at the bottom of the oceans.

It turns out that c is also the actual cost, because at the goal the h component is 0, and so the path cost is the total cost as estimated by the function.

But one of the first things I realized about the frontier that we don't have to look at the future to find it.

And if you're a biologist and know about sharks, and you want to assess, how much jeopardy am I really in here, there's one question that sort of jumps to the forefront of your mind immediately, which is (Video) Diver 1

Now the question I want you to answer is once we remove that from the frontier, what paths are we going to add next?

And Dr. Terry Erwin, in 1983, called the canopy, the last biotic frontier.

So we have so many problems here on earth, and if we want to solve those problems and really advance humanity, we need to continue to explore.

If you're talking about a factory setting, when you're talking about deciding to make one thing or another, then maybe you just aren't using the resources in an optimal way.

Then, when we consider a new path, we add the new state to the set of already explored states, and then when we are expanding the path and adding in new states to the end of it, we don't add that in if we have already seen that new state in either the frontier or the explored.

Azerbaijan was a forgotten corner of the Caucuses, but now with the Baku Tbilisi Ceyhan pipeline into Turkey, it has rebranded itself as the frontier of the west.