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-1
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-Okay, so let me look at the requirements and
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-2
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-it's something that I can see here that we didn't point out before is that
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-3
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-there seems to be clearly some concept of a due date. And I'm telling you why
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-4
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-I'm saying that because here, for example, I notice that it says when items are
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-5
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-due. We mention overdue several times, so is
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-6
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-this something we need to keep track of?
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->> Yeah remember when we used to stamp them on the books? In the stamp pad?
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-8
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->> Oh yeah yeah yeah! Oh course!
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-9
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->> Right? Yeah we definitely keep track of,
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-10
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-the system has to keep track of when books are due.
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-11
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->> Okay. So it seems to me that one good way
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-12
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-of doing that is by basically adding an attribute to the, item.
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-13
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->> Okay.
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-14
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->> And I'll just call it due date.
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-15
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->> Okay.
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-16
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->> So basically for each item in case it's loaned
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-17
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-there will be this attribute that will contain the value of
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-18
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->> Okay.
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-19
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->> Of when, when the item is due. And then, something else that I noticed
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-20
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-here is that down here, it seems like
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-21
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-the requirements are saying that an item can
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-22
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-be renewed only once. So, I guess, that's
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-23
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-something we need to keep track of, right?
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->> Yeah.
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->> The system needs to know.
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->> We have to know whether they've renewed it or not.
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->> Okay so, I'll do a similar thing here. I think I want to go and add a an
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-attribute that we'd call number of times renewed, and add it to the item class.
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->> Okay.
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->> And this is kind of more generic
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-than what you need, because here it says only once, but
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-let's say that in the future you want to allow it to,
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-kind of renew twice, you'll be able to use these attributes again
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-34
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-because, we can just count how many times it was renewed. Okay?
-
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->> Makes sense.
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->> Alright. And one last thing I want to point out.
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-And this seems obvious but I'm going to check with
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-38
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-you anyways. And seems like there is a basically the
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-need to keep track of whether an item is checked
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-out or not. If you look at the text here,
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-41
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-the requirements here, I can see that check out and checked out are
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-mentioned five times. So, I'm assuming that that's something also
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-that we want to know about an item, whether it's checked out or not.
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->> We have to keep track of whether they're checked out.
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->> Okay, so I'll add an
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-additional attribute there. So I'm going to again go
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-47
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-back to the diagram and I'm
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-48
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-just going to write here also the checked out attribute.
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-49
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-And, I think that's it as far as I'm
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-concerned. Is there anything that you think is missing?
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->> Well, I do have a question. Would checked out,
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-better not be the case that someone can check out a reference book.
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->> Oh, I see, I see.
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->> Okay. I mean, it's only the books and
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-the audio visual material that can be checked out.
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->> Right, right, right. Okay, so I, I guess, well the way I will fix that is,
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-I'll probably put yet another attribute in the item class, and I'll
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-call it loanable. And basically, this attribute is just telling us whether
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-an item is loanable or not. So, when it's not true and
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-loanable is not on. Basically, that item can be checked out.
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->> Okay. And, the system would know this.
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->> The system will know that.
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->> And prevent it from happening.
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->> And prevent it from happening. Okay?
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->> Alright.
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->> Perfect. So, we're going to do that and, any other objections,
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-67
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-any other?
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->> No, that was my question.
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->> Okay, perfect, so what I'm going to do next, I
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-mean, I haven't mentioned that yet, but you know classes right
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-now we just looked at the attributes right that give
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-you sort of the state of the class. And there's something
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-else, there's a second part of the class that is kind of
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-an orthogonal aspect, which is what the class can do. And we
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-call those operations. So normally these kinds also have operations, I
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-guess you know it would make sense to you as well.
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-And one way, one very natural way to
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-identify operations is to look at the requirements and
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-79
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-look for verbs. Because verbs associated with an item
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-will tell you basically what the item can do.
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->> Okay.
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->> So I, I'd like to go back to the requirements and
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-start, the same way in which we underlined, nouns, we're going to underline
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-verbs and we're going to see which ones of those verbs actually represent
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-actions that we want to represent explicitly, we want to model explicitly in
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-our class diagram.
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->> Okay.
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->> Okay.
-