From 8a7dfa0972c83fd811a4296e7373574bea4a28d0 Mon Sep 17 00:00:00 2001 From: Nguyễn Gia Phong Date: Sun, 19 Jul 2020 20:34:40 +0700 Subject: [usth/ICT2.7] Remove Udacity transcribes --- ...n & Aggregation Relationships - lang_en_vs5.srt | 219 --------------------- 1 file changed, 219 deletions(-) delete mode 100644 usth/ICT2.7/P2L2 OO Software Engineering and UML Subtitles/20 - Class Diagram: Association & Aggregation Relationships - lang_en_vs5.srt (limited to 'usth/ICT2.7/P2L2 OO Software Engineering and UML Subtitles/20 - Class Diagram: Association & Aggregation Relationships - lang_en_vs5.srt') diff --git a/usth/ICT2.7/P2L2 OO Software Engineering and UML Subtitles/20 - Class Diagram: Association & Aggregation Relationships - lang_en_vs5.srt b/usth/ICT2.7/P2L2 OO Software Engineering and UML Subtitles/20 - Class Diagram: Association & Aggregation Relationships - lang_en_vs5.srt deleted file mode 100644 index 8770928..0000000 --- a/usth/ICT2.7/P2L2 OO Software Engineering and UML Subtitles/20 - Class Diagram: Association & Aggregation Relationships - lang_en_vs5.srt +++ /dev/null @@ -1,219 +0,0 @@ -1 -00:00:00,080 --> 00:00:02,469 -The next example of relationship we're going to look at is - -2 -00:00:02,469 --> 00:00:06,740 -the association relationship. This is a relationship in which objects of - -3 -00:00:06,740 --> 00:00:09,570 -one class are connected to objects of another. And it's - -4 -00:00:09,570 --> 00:00:12,480 -called an has a relationship. So it means that objects of - -5 -00:00:12,480 --> 00:00:15,930 -one class have objects of another class. So let's see - -6 -00:00:15,930 --> 00:00:18,750 -what that means. Let's do it by considering two classes in - -7 -00:00:18,750 --> 00:00:22,370 -our example system. The student class and the course offering class. - -8 -00:00:22,370 --> 00:00:25,300 -In this case, there is an association between the student and - -9 -00:00:25,300 --> 00:00:28,010 -the course offering, because the student is registering for the - -10 -00:00:28,010 --> 00:00:31,750 -course offering. So, in a sense, the course offering has students. - -11 -00:00:31,750 --> 00:00:35,360 -Contains students, to indicate this fact we add a solid - -12 -00:00:35,360 --> 00:00:38,750 -line between the student class and the course offering. And the - -13 -00:00:38,750 --> 00:00:40,540 -fact that having a solid line doesn't really tell us - -14 -00:00:40,540 --> 00:00:44,780 -much about the nature of the relationship, so to clarify such - -15 -00:00:44,780 --> 00:00:47,550 -nature we can use what we call adornments that we - -16 -00:00:47,550 --> 00:00:51,010 -can apply to associations we can add to associations to clarify - -17 -00:00:51,010 --> 00:00:53,850 -their meaning. In particular we can add a label to - -18 -00:00:53,850 --> 00:00:57,550 -an association and the label describes the nature of the relationship. - -19 -00:00:57,550 --> 00:01:00,440 -In this case, for example, it clarifies that the student - -20 -00:01:00,440 --> 00:01:03,970 -registers for CourseOffering. We can also add a triangle to - -21 -00:01:03,970 --> 00:01:07,050 -further clarify the direction of the relationship. So in this - -22 -00:01:07,050 --> 00:01:10,240 -case, the triangle will indicate that it's the student That registers - -23 -00:01:10,240 --> 00:01:13,120 -for the course offering, and not the other way around. Another - -24 -00:01:13,120 --> 00:01:16,650 -important adornment or limitation that we can put on an association, - -25 -00:01:16,650 --> 00:01:20,800 -is multiplicity. Multiplicity defines the number of instances of one - -26 -00:01:20,800 --> 00:01:23,540 -class that are related to one instance of the other - -27 -00:01:23,540 --> 00:01:26,900 -class. We can define multiplicity at either end of the - -28 -00:01:26,900 --> 00:01:29,620 -relationship. In this case, for instance, we can say that - -29 -00:01:29,620 --> 00:01:31,890 -if we look at the student, the student can register - -30 -00:01:31,890 --> 00:01:35,410 -for two or more course offerings. Whereas, if we look - -31 -00:01:35,410 --> 00:01:37,560 -at the course offering, we can say that each course - -32 -00:01:37,560 --> 00:01:42,260 -offering can have or can enroll between 1 and 50 students. - -33 -00:01:42,260 --> 00:01:45,120 -So as you can see by adding a label, a direction, - -34 -00:01:45,120 --> 00:01:49,590 -and multiplicity, we make it much clearer what the relationship is - -35 -00:01:49,590 --> 00:01:52,170 -and what it means and what are its characteristics. As we - -36 -00:01:52,170 --> 00:01:55,130 -saw when we introduced relationships, there is a different kind of - -37 -00:01:55,130 --> 00:01:58,860 -association, kind of a specialized one, which we call aggregation. So - -38 -00:01:58,860 --> 00:02:01,130 -here we're going to look at an example of an aggregation. So - -39 -00:02:01,130 --> 00:02:03,490 -first of all what is an aggregation? An aggregation is a - -40 -00:02:03,490 --> 00:02:07,580 -relationship between 2 classes in which 1 represents a larger class - -41 -00:02:07,580 --> 00:02:10,610 -like a whole which consists of smaller classes which are - -42 -00:02:10,610 --> 00:02:13,430 -the parts of this whole. So lets look at an example - -43 -00:02:13,430 --> 00:02:16,960 -in the context of our system. Let's consider a Course - -44 -00:02:16,960 --> 00:02:19,160 -and the CourseOffering. And in this case, we can see - -45 -00:02:19,160 --> 00:02:23,000 -that the Course consists of multiple CourseOfferings. So in - -46 -00:02:23,000 --> 00:02:26,520 -a sense, a course is a whole and the course offerings - -47 -00:02:26,520 --> 00:02:29,430 -are the parts of this whole. So this a perfect case - -48 -00:02:29,430 --> 00:02:32,620 -in which we will use an aggregation to express this relationship. - -49 -00:02:32,620 --> 00:02:37,630 -So we will add a solid line with a diamond on the side of the whole class - -50 -00:02:37,630 --> 00:02:42,380 -to indicate that the course consists of multiple course offerings. - -51 -00:02:42,380 --> 00:02:44,670 -And as we did for associations even though we - -52 -00:02:44,670 --> 00:02:46,010 -are not going to do it for this specific - -53 -00:02:46,010 --> 00:02:49,540 -example, we could also in this case add multiplicity - -54 -00:02:49,540 --> 00:02:52,830 -information on the aggregation to indicate how many classes - -55 -00:02:52,830 --> 00:02:55,310 -of the two types are involved in the relationships. -- cgit 1.4.1