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diff --git a/usth/ICT2.7/P3L2 A Tale of Analysis and Design Subtitles/3 - Refining Classes and Attributes - lang_en.srt b/usth/ICT2.7/P3L2 A Tale of Analysis and Design Subtitles/3 - Refining Classes and Attributes - lang_en.srt deleted file mode 100644 index 271c2fd..0000000 --- a/usth/ICT2.7/P3L2 A Tale of Analysis and Design Subtitles/3 - Refining Classes and Attributes - lang_en.srt +++ /dev/null @@ -1,535 +0,0 @@ -1 -00:00:00,880 --> 00:00:03,920 -Okay, so this is our first, class diagram. - -2 -00:00:03,920 --> 00:00:06,260 ->> So, let me ask you something about. - -3 -00:00:06,260 --> 00:00:06,520 ->> Okay. - -4 -00:00:06,520 --> 00:00:08,930 ->> What we've done so far. I also sent, in what - -5 -00:00:08,930 --> 00:00:14,490 -I sent you, I also had some stories about how the actual - -6 -00:00:14,490 --> 00:00:16,400 ->> Library is used. You asked me to do - -7 -00:00:16,400 --> 00:00:18,950 -that and are we going to take, use that here? - -8 -00:00:20,160 --> 00:00:23,300 ->> Glad you asked actually. yeah. Those are, you know, what we call use - -9 -00:00:23,300 --> 00:00:25,940 -cases, or what we will use as scenarios kind of things that we will - -10 -00:00:25,940 --> 00:00:28,340 -use to derive use cases. And they're also a very good - -11 -00:00:28,340 --> 00:00:31,450 -way of extracting requirements. We're not going to look at them right - -12 -00:00:31,450 --> 00:00:33,890 -now because now, because we're more working on kind of the static - -13 -00:00:33,890 --> 00:00:37,860 -structure of the system. But after we're done with the class diagram, - -14 -00:00:37,860 --> 00:00:40,700 -you know, we will do it at a different time. But - -15 -00:00:40,700 --> 00:00:43,410 -we're going to use those to see how the - -16 -00:00:43,410 --> 00:00:45,850 -libraries actually use them, and see whether we can get more - -17 -00:00:45,850 --> 00:00:49,000 -information that we can use to refine our requirements based on that. - -18 -00:00:49,000 --> 00:00:49,770 ->> Okay. - -19 -00:00:49,770 --> 00:00:51,020 ->> Okay, - -20 -00:00:51,020 --> 00:00:52,940 -So, for now, we'll just focus in on the, - -21 -00:00:52,940 --> 00:00:54,630 -structure, but, just so you know, I'm, - -22 -00:00:54,630 --> 00:00:55,870 -I'm glad you sent them, because they were going - -23 -00:00:55,870 --> 00:00:57,380 -very useful as well. - -24 -00:00:59,410 --> 00:01:00,840 -Okay. So let's see. Well, first of all, let - -25 -00:01:00,840 --> 00:01:03,030 -me, seems like that this is already pretty crowded, - -26 -00:01:03,030 --> 00:01:06,770 -right? We have a number of, classes. So let's - -27 -00:01:06,770 --> 00:01:10,580 -see if there's, some class that may be superfluous and - -28 -00:01:10,580 --> 00:01:13,310 -we can model in a different way. So, for - -29 -00:01:13,310 --> 00:01:16,360 -example, you, while, while thinking of this I was thinking, - -30 -00:01:16,360 --> 00:01:19,450 -the library card, it doesn't really contain much - -31 -00:01:19,450 --> 00:01:22,736 -information, right? So is it basically just the number? - -32 -00:01:22,736 --> 00:01:23,948 - -33 -00:01:23,948 --> 00:01:30,760 -The card has a number on it. We have a separate vendor that does that for us so. - -34 -00:01:30,760 --> 00:01:30,810 ->> Oh. - -35 -00:01:30,810 --> 00:01:33,270 ->> We don't need, it doesn't need to be part of this system, - -36 -00:01:33,270 --> 00:01:35,450 -we just have to make sure that every patron has a library card. - -37 -00:01:35,450 --> 00:01:37,670 ->> Okay, so basically for you, in a sense, the library - -38 -00:01:37,670 --> 00:01:41,560 -card is just an ID that gets associated with a patron. - -39 -00:01:41,560 --> 00:01:42,120 ->> That's right. - -40 -00:01:42,120 --> 00:01:45,380 ->> So I think that the best way to represent this, I mean, unless you - -41 -00:01:45,380 --> 00:01:47,000 -need an entity because you are creating it - -42 -00:01:47,000 --> 00:01:49,160 -yourself, but it seems like you are not. - -43 -00:01:49,160 --> 00:01:52,710 -I would just remove this one and I would like to put this, - -44 -00:01:52,710 --> 00:01:56,020 -basically to take the library card number and add it to the pattern. - -45 -00:01:56,020 --> 00:01:57,100 ->> Okay, makes sense. - -46 -00:01:57,100 --> 00:02:03,000 ->> Okay, so I'll add it here. And as - -47 -00:02:03,000 --> 00:02:06,160 -an additional attribute. Okay, and it will eliminate this class. - -48 -00:02:06,160 --> 00:02:06,410 ->> Okay. - -49 -00:02:06,410 --> 00:02:07,580 ->> Okay. - -50 -00:02:09,690 --> 00:02:11,700 -Oh, and, wait a second, so I guess - -51 -00:02:11,700 --> 00:02:13,940 -also the child needs a library card number, right? - -52 -00:02:13,940 --> 00:02:18,320 ->> Child needs a library card number, but let me ask you about that. Is, - -53 -00:02:18,320 --> 00:02:22,050 -is child a separate class, or is it just another kind of patron? - -54 -00:02:22,050 --> 00:02:24,920 ->> Oh, I see, I see. Because, yeah, it - -55 -00:02:24,920 --> 00:02:28,490 -is sort of a special patron, right? And, so - -56 -00:02:28,490 --> 00:02:31,730 -maybe we should, maybe we should represent it as - -57 -00:02:31,730 --> 00:02:35,640 -a kind of a refinement of the patron. - -58 -00:02:35,640 --> 00:02:38,730 -Hm, but then that made me think. So what is - -59 -00:02:38,730 --> 00:02:42,510 -the only thing that characterizes children? Is it just the age? - -60 -00:02:42,510 --> 00:02:47,440 ->> Well, if they're, that they can't check out more than five books. - -61 -00:02:47,440 --> 00:02:48,890 ->> Okay. And the, and the only difference is the - -62 -00:02:48,890 --> 00:02:52,010 -fact that they are less than, you know, twelve years old. - -63 -00:02:52,010 --> 00:02:52,710 ->> Twelve or less, right. - -64 -00:02:52,710 --> 00:02:56,090 ->> Twelve or less. So, I guess, you know, I would probably - -65 -00:02:56,090 --> 00:03:01,120 -like to represent this by making the age explicit in the patron rather - -66 -00:03:01,120 --> 00:03:04,730 -than to represent it as a class. And I'll tell you why, - -67 -00:03:04,730 --> 00:03:08,300 -because one, one of the issues, and you know, that might happen - -68 -00:03:08,300 --> 00:03:13,070 -again, is that, basically, there are patrons that are children. And they're - -69 -00:03:13,070 --> 00:03:17,130 -no longer children, when they come you know 13 or older right. - -70 -00:03:17,130 --> 00:03:18,100 ->> Right. - -71 -00:03:18,100 --> 00:03:21,990 ->> And if we represent them with a separate class in a sense, then we - -72 -00:03:21,990 --> 00:03:26,620 -cannot really change the type of an instance of these classes. - -73 -00:03:26,620 --> 00:03:28,920 -So we're left to kind of destroy the patron, create - -74 -00:03:28,920 --> 00:03:31,190 -a new one, so that means we also have to transfer - -75 -00:03:31,190 --> 00:03:33,510 -any history we want to keep history and so on. - -76 -00:03:33,510 --> 00:03:35,680 -So I, I think I kind of like better the idea - -77 -00:03:35,680 --> 00:03:39,560 -that I represent the age exclusively in - -78 -00:03:39,560 --> 00:03:42,700 -the patron, and then I'll behave differently, based on whether the - -79 -00:03:42,700 --> 00:03:45,910 -patron is 12 years old, or younger, or 13 or, - -80 -00:03:45,910 --> 00:03:49,600 -13 or older. This, do you see any problem with that? - -81 -00:03:49,600 --> 00:03:51,210 ->> It makes things a little simpler. - -82 -00:03:51,210 --> 00:03:51,490 ->> Okay, - -83 -00:03:51,490 --> 00:03:53,550 -and we actually, it allows us also to eliminate - -84 -00:03:53,550 --> 00:03:56,450 -one class here. So I'm going to proceed this way. - -85 -00:03:56,450 --> 00:03:59,450 -I'm going to eliminate the children class, and I'm going to - -86 -00:03:59,450 --> 00:04:03,600 -put the age in the patron. Okay, and let me - -87 -00:04:03,600 --> 00:04:07,020 -see. But in this spirit, actually, something else that jumps - -88 -00:04:07,020 --> 00:04:09,740 -at me is this idea of the bestseller, because I - -89 -00:04:09,740 --> 00:04:11,850 -kind of feel like, we might have the same - -90 -00:04:11,850 --> 00:04:15,085 -problem. So, what is the story? What is a bestseller. - -91 -00:04:15,085 --> 00:04:16,850 ->> Well it's - -92 -00:04:16,850 --> 00:04:20,750 -an item that we want to restrict how - -93 -00:04:20,750 --> 00:04:23,896 -long people can keep, because there is such demand for it. - -94 -00:04:23,896 --> 00:04:26,880 ->> I see, and so basically a book that's a - -95 -00:04:26,880 --> 00:04:30,450 -bestseller, like the New York Times bestseller, is a bestseller forever? - -96 -00:04:30,450 --> 00:04:32,683 ->> No, no, no it's hot for - -97 -00:04:32,683 --> 00:04:35,940 -awhile, and then it becomes just a regular item. - -98 -00:04:35,940 --> 00:04:38,318 ->> I see. Hm. Then I guess it's a - -99 -00:04:38,318 --> 00:04:40,349 -similar situation to the one I was mentioning before, right? - -100 -00:04:40,349 --> 00:04:40,980 ->> Okay. - -101 -00:04:40,980 --> 00:04:41,800 ->> That if we have a book, - -102 -00:04:41,800 --> 00:04:44,530 -it will kind of have to change its type if it becomes a best seller. - -103 -00:04:44,530 --> 00:04:47,218 -Then we have to change its type again, if it's no longer a best seller. - -104 -00:04:47,218 --> 00:04:47,790 ->> Right. - -105 -00:04:47,790 --> 00:04:48,920 ->> So it seems to me that a better - -106 -00:04:48,920 --> 00:04:52,150 -way to represent this, is just to eliminate this BestSeller - -107 -00:04:52,150 --> 00:04:55,060 -class and instead, I'm going to put the best seller - -108 -00:04:55,060 --> 00:04:58,190 -attribute, which would just be a Boolean in the book. - -109 -00:04:58,190 --> 00:05:00,190 ->> Okay, what do you mean by Boolean? - -110 -00:05:00,190 --> 00:05:02,280 ->> Right. We don't know what Boolean is, right? The Boolean is - -111 -00:05:02,280 --> 00:05:04,940 -basically just a number. It can have two values, right? True or false. - -112 -00:05:04,940 --> 00:05:05,380 ->> Okay. - -113 -00:05:05,380 --> 00:05:06,830 ->> So we usually, normally use it - -114 -00:05:06,830 --> 00:05:09,510 -in this in this case. Imagine one, zero, - -115 -00:05:09,510 --> 00:05:10,970 -right? Then it's just kind of the basic. - -116 -00:05:10,970 --> 00:05:11,120 ->> Okay. - -117 -00:05:11,120 --> 00:05:12,250 ->> You know, the bits, right? - -118 -00:05:12,250 --> 00:05:12,590 ->> Okay. - -119 -00:05:12,590 --> 00:05:14,730 ->> So, this is just telling us, it's like a flag - -120 -00:05:14,730 --> 00:05:16,672 -that is telling this book is a best seller, or not. - -121 -00:05:16,672 --> 00:05:17,053 ->> Okay. - -122 -00:05:17,053 --> 00:05:20,920 ->> It's very easy to change this value and make a book a best - -123 -00:05:20,920 --> 00:05:22,880 -seller or not a best seller, than - -124 -00:05:22,880 --> 00:05:26,210 -just creating and destroying instances of these classes. - -125 -00:05:26,210 --> 00:05:27,135 ->> Okay, makes sense. - -126 -00:05:27,135 --> 00:05:32,630 ->> Okay, so at this point, this already looks better, right? Because we have, - -127 -00:05:32,630 --> 00:05:35,590 -less classes, and I think we did, yeah, we - -128 -00:05:35,590 --> 00:05:38,775 -did some serious cleanup. That's good. Okay, so now that - -129 -00:05:38,775 --> 00:05:40,975 -we eliminated some of this, what I would like to - -130 -00:05:40,975 --> 00:05:42,845 -do, as I said, we are going to both clean - -131 -00:05:42,845 --> 00:05:45,222 -up, but also refine. I would like to go - -132 -00:05:45,222 --> 00:05:48,826 -back to our, requirements and see whether we can identify - -133 -00:05:48,826 --> 00:05:52,566 -additional attributes for this, class that maybe are not as - -134 -00:05:52,566 --> 00:05:55,120 -obvious as the one that we saw so far, okay? - |