1
00:00:00,110 --> 00:00:04,700
We now discuss UML's behavioral diagrams. Those diagrams that

2
00:00:04,700 --> 00:00:07,490
have to do with the behavior, the dynamic aspects

3
00:00:07,490 --> 00:00:09,940
of the system, rather than the static ones. The

4
00:00:09,940 --> 00:00:12,670
first behavioral diagram I want to discuss is a very

5
00:00:12,670 --> 00:00:15,590
fundamental one, the Use Case Diagram. So, let's start

6
00:00:15,590 --> 00:00:18,370
by seeing what a Use Case is. A Use Case

7
00:00:18,370 --> 00:00:21,800
represents two main things. First the sequence of interactions

8
00:00:21,800 --> 00:00:25,250
of outside entities which is what we normally call actors

9
00:00:25,250 --> 00:00:27,990
with the system that we're modelling and the second thing

10
00:00:27,990 --> 00:00:32,290
is the system actions that yield an observable result of values

11
00:00:32,290 --> 00:00:35,380
to the actors. And basically these two things, and nothing else

12
00:00:35,380 --> 00:00:38,010
that the outside view of the system. So the view of

13
00:00:38,010 --> 00:00:41,060
the system in which we look at the interaction between

14
00:00:41,060 --> 00:00:44,170
this system, and the outside world. If you want to parallel, think

15
00:00:44,170 --> 00:00:48,070
about designing a house. Considering how you would use the house.

16
00:00:48,070 --> 00:00:50,550
And you might have seen use cases called with different names.

17
00:00:50,550 --> 00:00:54,820
So for example, they're also called scenarios, scripts or user stories,

18
00:00:54,820 --> 00:00:58,220
but in the context of UML, we'll call the use cases.

19
00:00:58,220 --> 00:01:00,650
Now let's look at the basic notation for a use case,

20
00:01:00,650 --> 00:01:03,910
which is fairly simple. We have a use case which is represented

21
00:01:03,910 --> 00:01:05,760
by an oval, with a name, which is the name of

22
00:01:05,760 --> 00:01:08,520
the use case. We have an actor, which is represented by

23
00:01:08,520 --> 00:01:12,330
this icon and is normally identified by a role name. And

24
00:01:12,330 --> 00:01:15,820
finally we have an edge which is a solid line that connects

25
00:01:15,820 --> 00:01:18,970
actors and use cases and indicates that an actor

26
00:01:18,970 --> 00:01:21,270
is the actor of a given use case. And just

27
00:01:21,270 --> 00:01:24,360
for completeness let me note there are some additional notational

28
00:01:24,360 --> 00:01:27,750
elements but now for simplicity we'll just use these ones.