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1
00:00:00,350 --> 00:00:03,460
Spencer, I gotta tell you, I'm impressed.
2
00:00:03,460 --> 00:00:05,441
You're getting very good at this. So, why
3
00:00:05,441 --> 00:00:07,190
don't you go wild and continue, there
4
00:00:07,190 --> 00:00:09,240
anything else you think we can improve here?
5
00:00:09,240 --> 00:00:11,800
>> Well something was bothering
6
00:00:11,800 --> 00:00:14,600
me, that what happens if there's more
7
00:00:14,600 --> 00:00:19,110
than one book with the same title and somebody puts in a request?
8
00:00:19,110 --> 00:00:25,360
>> Oh, I see. That's a good point. So basically what you are telling me is
9
00:00:25,360 --> 00:00:28,630
there's kind of a difference between an item and
10
00:00:28,630 --> 00:00:30,660
the title, so the title is kind of a more
11
00:00:30,660 --> 00:00:32,940
general concept, in a sense. So if you can
12
00:00:32,940 --> 00:00:35,830
have multiple copies of a given title, is that right?
13
00:00:35,830 --> 00:00:38,460
>> Yeah, we have five copies of Tom Sawyer, and the
14
00:00:38,460 --> 00:00:42,810
persons, the patrons, really putting in a request for any Tom Sawyer.
15
00:00:42,810 --> 00:00:45,332
>> They don't want like copy number three of Tom Sawyer, right? They want,
16
00:00:45,332 --> 00:00:50,530
they want to read Tom Sawyer. Okay and I can represent that. So, in which
17
00:00:50,530 --> 00:00:55,230
I suggest we do that, and you can tell me whether it makes sense to you is by
18
00:00:55,230 --> 00:00:59,650
introducing an additional class, which I call Title. And
19
00:00:59,650 --> 00:01:02,614
that represents exactly the concept that you're mentioning. So
20
00:01:02,614 --> 00:01:04,666
this is a title which represents some
21
00:01:04,666 --> 00:01:09,180
specific content. That is not related to a specific
22
00:01:09,180 --> 00:01:12,110
physical element. Like it can be rated to multiple,
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00:01:12,110 --> 00:01:15,520
physical elements. So basically I'm going to create this title.
24
00:01:15,520 --> 00:01:18,100
And then I'm going to create a relationship between
25
00:01:18,100 --> 00:01:20,500
the title and the item. And what
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00:01:20,500 --> 00:01:22,530
the relationship is telling me, the the association
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00:01:22,530 --> 00:01:25,512
between these two in this case. Is an association,
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00:01:25,512 --> 00:01:30,320
that we call aggregation. So it's a special kind of association, that basically
29
00:01:30,320 --> 00:01:35,450
indicates that an item of this type, so a title can
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00:01:35,450 --> 00:01:40,692
consist of a multiple elements of this type of multiple items.
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00:01:40,692 --> 00:01:42,710
So it's telling me that one title can
32
00:01:42,710 --> 00:01:45,700
consist of multiple items, and I'm going to indicate
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00:01:45,700 --> 00:01:48,560
it with this annotation, which is a this
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00:01:49,700 --> 00:01:53,200
diamond at the top of the association.
35
00:01:53,200 --> 00:01:55,570
>> And so we can move our request
36
00:01:55,570 --> 00:01:57,510
line, up from loanable item to
37
00:01:57,510 --> 00:01:59,010
title, because that's what they're really requesting.
38
00:01:59,010 --> 00:02:00,710
>> Definitely, definitely, and in fact,
39
00:02:00,710 --> 00:02:02,420
you know, that represents exactly the situation
40
00:02:02,420 --> 00:02:06,350
that you are mentioning, at this point when the patron makes a request.
41
00:02:06,350 --> 00:02:12,240
It makes a request to a title and not to a loanable item. And then, and
42
00:02:12,240 --> 00:02:15,420
when the actual loan will take place,
43
00:02:15,420 --> 00:02:18,420
then that will be connected to a specific item.
44
00:02:18,420 --> 00:02:20,090
>> Right. Okay that makes sense.
45
00:02:20,090 --> 00:02:20,388
>> Makes sense?
46
00:02:20,388 --> 00:02:20,779
>> Yeah.
47
00:02:20,779 --> 00:02:21,214
>> Okay, good.
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