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diff --git a/usth/ICT2.7/P2L2 OO Software Engineering and UML Subtitles/33 - State Transition Diagram Example - lang_en_vs5.srt b/usth/ICT2.7/P2L2 OO Software Engineering and UML Subtitles/33 - State Transition Diagram Example - lang_en_vs5.srt deleted file mode 100644 index 6c4c1bf..0000000 --- a/usth/ICT2.7/P2L2 OO Software Engineering and UML Subtitles/33 - State Transition Diagram Example - lang_en_vs5.srt +++ /dev/null @@ -1,227 +0,0 @@ -1 -00:00:00,090 --> 00:00:02,850 -As usual were going to illustrate these kind of diagrams by - -2 -00:00:02,850 --> 00:00:06,050 -using an example. In particular we are going to describe the state - -3 -00:00:06,050 --> 00:00:09,330 -transition diagram for part of our example, for part of - -4 -00:00:09,330 --> 00:00:12,640 -our course management system. And we're going to focus on the course - -5 -00:00:12,640 --> 00:00:15,540 -offering class. When the class is created, it enters the - -6 -00:00:15,540 --> 00:00:19,490 -initialization state, in which the activity performed is to initialize the - -7 -00:00:19,490 --> 00:00:22,580 -course. At this point, a simple case is the case in - -8 -00:00:22,580 --> 00:00:25,550 -which the class is cancelled, so there is a cancelled event. - -9 -00:00:25,550 --> 00:00:28,700 -And if that happens, the class is simply cancelled. So it - -10 -00:00:28,700 --> 00:00:31,720 -gets into this final state, which is the state cancelled. And - -11 -00:00:31,720 --> 00:00:35,500 -the activity in this case is to notify the registered students. - -12 -00:00:35,500 --> 00:00:38,580 -Obviously if this is the flow there will be no registered students. - -13 -00:00:38,580 --> 00:00:41,110 -However something else can happen when we are in this initial - -14 -00:00:41,110 --> 00:00:43,930 -state. So what can happen is that a student can register, so - -15 -00:00:43,930 --> 00:00:47,260 -in this case the add student event is triggered. And the - -16 -00:00:47,260 --> 00:00:50,620 -corresponding action is to set the count, in this case it would - -17 -00:00:50,620 --> 00:00:53,270 -be the count of students for the course offering, to one. And - -18 -00:00:53,270 --> 00:00:55,570 -there will be a change of state and the course offering will - -19 -00:00:55,570 --> 00:00:58,870 -get into this open state. And the action that will be performed - -20 -00:00:58,870 --> 00:01:02,260 -on entry will be to register the student. At this point more - -21 -00:01:02,260 --> 00:01:06,920 -students may register. So other student events might occur and notice that we - -22 -00:01:06,920 --> 00:01:10,630 -have a curve here that tells us this event will trigger this - -23 -00:01:10,630 --> 00:01:13,790 -transition only if the count is less than 10. So we're assuming - -24 -00:01:13,790 --> 00:01:16,120 -that we're not going to have more than 10 students just for lack - -25 -00:01:16,120 --> 00:01:19,010 -of a better number in our course offering. So if that - -26 -00:01:19,010 --> 00:01:21,960 -happens, if the count is less than ten so then the count - -27 -00:01:21,960 --> 00:01:25,880 -is incremented so the increment count action takes place. And the - -28 -00:01:25,880 --> 00:01:28,910 -system goes back into the open state, and the new student - -29 -00:01:28,910 --> 00:01:32,100 -is registered. Now here we have an interesting transition, because there's - -30 -00:01:32,100 --> 00:01:35,380 -no event triggering the transition, but simply the fact that the - -31 -00:01:35,380 --> 00:01:37,780 -count is equal to 10. So you can imagine this as - -32 -00:01:37,780 --> 00:01:40,930 -being a transition that is always enabled so can always be triggered, - -33 -00:01:40,930 --> 00:01:43,410 -but will be guarded. By the fact that the count has - -34 -00:01:43,410 --> 00:01:46,750 -to be exactly ten. So basically this transition will take place - -35 -00:01:46,750 --> 00:01:49,800 -only when enough students are added, such we get to count - -36 -00:01:49,800 --> 00:01:52,900 -them. Being incremented and being equal to ten and then the transition - -37 -00:01:52,900 --> 00:01:55,590 -will occur. And we will get into the closed state, in - -38 -00:01:55,590 --> 00:01:59,025 -which the class is no longer open because there are enough students - -39 -00:01:59,025 --> 00:02:01,730 -registered. And at this point, what will happen is that the - -40 -00:02:01,730 --> 00:02:06,320 -course will be finalized. So there will be this activity which performs - -41 -00:02:06,320 --> 00:02:09,699 -some operation that is needed to finalize the course. Another possibility - -42 -00:02:09,699 --> 00:02:12,150 -is that when we are in the open state, the course - -43 -00:02:12,150 --> 00:02:14,680 -is cancelled. And if the course is cancelled, in this case, - -44 -00:02:14,680 --> 00:02:18,320 -we go again to the cancel state. But here, the activity - -45 -00:02:18,320 --> 00:02:21,850 -of notifying registered students makes more sense. Because we will have - -46 -00:02:21,850 --> 00:02:24,960 -at least one registered student in this state, and therefore we'll - -47 -00:02:24,960 --> 00:02:28,190 -need to notify such student that the course offering has been - -48 -00:02:28,190 --> 00:02:31,470 -cancelled. Finally, is it also possible also to cancel a course - -49 -00:02:31,470 --> 00:02:34,050 -after it has been closed? And in this case again, the - -50 -00:02:34,050 --> 00:02:38,040 -same thing will happen. The class will reach the cancelled state and - -51 -00:02:38,040 --> 00:02:40,850 -all the students, in this case ten students, that are registered - -52 -00:02:40,850 --> 00:02:43,730 -for the course will be notified that the course has been cancelled. - -53 -00:02:43,730 --> 00:02:46,100 -So, if we look at this state transition diagram, you can - -54 -00:02:46,100 --> 00:02:49,860 -see that it's pretty easy to see what the evolution of objects - -55 -00:02:49,860 --> 00:02:52,590 -of this class can be. How they can go from their initial - -56 -00:02:52,590 --> 00:02:56,660 -state to various final states depending on what are the external events - -57 -00:02:56,660 --> 00:02:57,750 -that reach the system. |