1 files changed, 535 insertions, 0 deletions

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
new file mode 100644
index 0000000..271c2fd
--- /dev/null
+++ b/usth/ICT2.7/P3L2 A Tale of Analysis and Design Subtitles/3 - Refining Classes and Attributes - lang_en.srt
@@ -0,0 +1,535 @@
+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?
+