path: root/usth/ICT2.7/P3L2 A Tale of Analysis and Design Subtitles/2 - Analyzing Requirements - lang_en.srt

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Okay so let me start underlining these nouns, and I'll start

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identifying the ones that are relevant, and I'll ask you some

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questions or you can ask me questions if

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you see something that doesn't make sense to you. Good enough.

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>> okay, let's see, patron. It seems to

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me that patron is definitely an important entity.

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>> That's, that's what its all about.

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>> Okay, all right, so actually, the way

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I'm going to do this, I'm going to take all these relevant

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entities and I'm going to start putting them into what I call a class

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diagram. So you don't really need to know what that is exactly, but imagine

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this being a, a diagram in which I'm drawing, I represent in all development

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items as rectangles with a given name and, and then later on some attributes.

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>> Okay.

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>> Okay, and I'm, I'm just going to put

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them there. So I'm going to start with patron.

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I'm going to create one class for the

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patron. I'm going to give it the name patron.

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And by the way, assuming that you'd probably figure out, it's important that we

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represent, we use the right names so that it's clear when we're looking at

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the class diagram what we're referring to, so I'll just use the, the nouns

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themselves as names. Okay, library card seems to be also a relevant element.

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>> Every patron has a library card.

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>> All right, perfect, so we'll just

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create a library card here. And let's see.

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As, as long as they're in the system. And I saw that there's a system

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here, this concept of system, this concept

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of library. And based on my experience, normally,

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those are kind of in an overarching themes. So this is really what we are

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modeling. So the only

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thing that will make a difference is

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if there were more than one library or more than one system. Is that the case?

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>> We just want one system for our one library

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>> Okay so, in this case I won't even represent

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those because basically what I'm representing is the system and

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the library.

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>> I understand, I understand.

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Okay and then, oh name, address and phone

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number are interesting because these are important entities,

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but this seems like, you know, they're not

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entities in themselves, so they're more attributes

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of something else. I would imagine that

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this is the way you identify, or these

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are elements that are important for the patron?

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>> That's what we take down when we issue the cards.

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>> Okay. Perfect. So, I'm going to

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take those and make those attributes of the patron, which means

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that I'm going to take the class that I created before, and I'm

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just going to write them down here so that they're represented and,

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and we know that these are kind of what characterizes the patron.

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>> Gotcha.

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>> Okay? And then, I guess similar consideration for the library

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card number. So this is to be associated with the library card?

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>> It's printed right on it.

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>> All right, so we'll put this as

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an attribute of the library card, then. And then, in addition, at any particular point

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in time. Okay, so time seems to be a relevant entity right,

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because time seems to occur several times in this description. For example, I

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think you guys keep track of how long a book has been loaned, right?

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>> Right.

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>> And there's some time associated also here.

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>> And a children's age.

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>> Oh yeah. The children's age here that

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I didn't see before. Yeah. So, what

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I'm going to do, I'm going to represent this in

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a sort of generic way, as a date.

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>> Okay.

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>> These are kind of, kind of classes, utility

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classes we call them, that are normally in every system.

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>> Okay.

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>> So I'm just going to put it down here

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as a utility class that will be used

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by different elements in the diagram. Okay, so

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I want to calculate the items. So the items also

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I mean I for what I know about libraries they

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seem to be pretty relevant elements, right? So these are all

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>> This is what we check out, this is what we're for.

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>> Okay, so then items definitely will become a

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class, and then we have a due. Oh there's also

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this concept of fines. I guess that seems to be

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important. Right? You guys give fines to people who are late.

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>> Right, right.

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>> Right, collect fines and so on. So we create a fine class down here and

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the children. So children are special customers, right? It's

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their age makes a difference? Is that the way it works?

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>> Right. They, they can only check out a few books.

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>> Okay. So I'll create them a special

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kind of case, a special kind of customer so

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I just create here a class for children. And

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I can see that they're categorized by their age.

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>> Right.

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>> So I'll just put the age here as an attribute of the child.

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And, okay, so the next one is

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restriction. And restriction is kind of tricky because just

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to be sort of a general concept. I mean,

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in a sense, all of those are restrictions, right?

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>> Right, this is just another one of these requirements.

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>> Oh, okay, so, so we don't need to represent it explicitly, right?

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>> Right, right.

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>> It's just telling us how the children, yeah, okay, right; this is

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just another requirement, so I just won't consider that for now. And oh,

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I see that these books and audio video materials, I guess these

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are things that the patrons can check out, right?

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>> Those are some of the items, right.

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>> There are two

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more down here, right? Reference books and magazines?

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>> But, they can't be checked

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out, but they're definitely in the library.

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>> Okay, so then I'm going to represent all of those

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actually, now. So, I'm going to have books, I'm going to have audio

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video materials, reference books, and magazines. And

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I'm just going to have those as classes. Then,

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okay here we have week, and we

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already represented this general concept of time, so

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week will be represented by the date class as well. And oh, I see best sellers.

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So best sellers are also, I guess, items that can be checked out, right?

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>> Right.

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>> Okay, so I'll

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just represent those as a class as well and an additional item that

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is relevant for the library. And the limit, this is also a time limit, right?

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>> Right.

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>> So it can also be represented with a, with a class.

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Oh, here we have cents, and for cents, same consideration that made

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for time. This is kind of the money, is a general concept

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that in all currency, many, in many IT systems. So, I'm, I'm

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going to just have a money class here, which is another utility class.

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>> Okay

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>> Okay, and, oh, here I have value, so value is a property.

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Let me look again at the requirement. Oh, it's the value of the item. So value

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I'm going to put in the item as an attribute. Okay?

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>> Okay. That's how much it cost us.

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>> Okay. Perfect.

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>> Seems like we got them all. Right? Anything I forgot?

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>> That looks like it.

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>> Okay, so this one, what I'd like to do. We have a kind of

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a first take, first cut at the class diagram. I'd like to kind of

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move to that and go through the different classes with you. And I'll ask

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you some questions again. And you can

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tell me whether there is something that

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jumps at you that's not right. And

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then we're going to try to refine that.

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>> Okay

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>> Okay.

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>> Sounds good.