'Verb' refers to the predicate verb. Predicate verbs change their form depending on the subject and the time expressed.

For example, I'll show you the successor state axiom for the In predicate.

If we have a predicate Possible of A and S, is an action A possible in a state?

But over here on the right I've put this sort of if conditional, a guard or a predicate we might call it in mathematics, and this is saying I only want you to yield those numbers for which the predicate is true.

So for all A and S for which it's possible to execute A in situation S, the In predicate holds if and only if the action was a load or the In predicate used to hold in the previous state and the action is not an unload.

If it's con , by convention, if a method returns a inaudible , or is a predicate, you end up with a, a question mark.

And the convention is that they refer to a specific situation, and we always put that situation argument as the last in the predicate.

And now instead of describing the actions that are applicable in a situation with a predicate Actions of S, situation calculus for some reason decided not to do that and instead we're going to talk about the actions that are possible in the state, and we're going to do that with a predicate.

The predicate is that part that shows the action in the sentence. In Japanese it would be the part that ends in da , suru , etc.

Instead of writing 1 action or 1 schema or 1 axiom for each action, we do 1 for each fluent, for each predicate that can change.

If that's true, then the In predicate holds between some cargo C and some plane in the state, which is the result of executing action A in state S.

For loops are structured essentially the same way they are in C, were we have an initializer value, then a predicate to evaluate for, when the for loop should end, and then an expression to execute at the end of each for loop.

If statements work essentially the same way that they would in any other language, where you have the keyword if, then in parenthesis you specify the predicate that's going to return a boolean value, either true or false and then the body of the if statement that executes, if that evaluates to true.

And then we start branching on the possible actions, so say one possible action would be to load the cargo, C1, onto the plane, P1, at SFO, and then that would bring us to another state which would have a different set of state variables set, and we'd continue branching out like that until we hit a state which satisfied the goal predicate.

So that In predicate will hold if and only if either A was a load action so if we load the cargo into the plane, then the result of executing that action A is that the cargo is in the plane or it might be that it was already true that the cargo was in the plane in situation S and A is not equal to an unload action.