OK

so welcome everybody.

Small message to the Zoomies who have failed in the ice bucket

challenge

namely succumb to the snow outside.

We have three people in presence.

If it gets much below that

I'm not going to give the course.

OK

so three is the official lower boundary.

And so since there is material enough

I'll be very happy to not give the course.

No.

Why would I preach to an empty room?

This says not actually being able to talk to people is

I'm a professor and a teacher

not an actor.

They can kind of imagine their audience.

I don't.

So you may want to think about SMAI.

There we go.

The other side of things.

And I want my this thing here.

And now we can start.

Good, so we've been talking about graphs and trees.

The upshot of this is that graphs and trees

are very important data structures in computer science

and symbolic artificial intelligence.

A graph is just a set of nodes or vertices

and a set of edges

which is just a relation

if you want.

A set of pairs of nodes.

And we draw them.

We have nodes.

We have edges between them.

We have two kinds of graphs in computer science.

The directed graphs actually are more important.

We've talked about when we consider two graphs the same

i.e., if they're isomorphic.

We've talked about labeled graphs,

things that might have one

two

three as labels on the nodes.

We're not interested in the objects that are the nodes.

They're just scaffolding or architecture.

We want to have something there.

We have to have a labeling function.

And we may also label the edges.

No.