WEBVTT

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Hello.
I am Alejandro Rodríguez Ascaso,

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lecturer at the Department
of Artificial Intelligence at UNED.

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In this video, we are going to look
at how to develop a use case,

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which is part of a broader task:
the creation of user requirements.

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As part of this creation
of user requirements,

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we need to describe

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 the functional requirements
of the system;

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that is, what the user
does with the system.

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We do not utilise use cases
to describe how the interaction

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between the user
and the system takes place.

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We describe the function,

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but to explain
how that interaction occurs,

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we will prepare
the non-functional requirements.

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A use case represents
the vision the system has

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of a user who is external to it.

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It expresses a transaction,

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an interaction
between the user and the system.

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For example, a user calling a lift,

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a peripheral requesting data
from a central computer,

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as in the case we are about to see,

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a person who uses speech recognition
to use their computer,

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and, specifically,
to edit a text document. 

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(CLAUDIA) I am going to show you
the speech-recognition system that I use:

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Dragon NaturallySpeaking.

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This software must be purchased.

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You install the software like any other,

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and once that's done,
you automatically begin training it.

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To improve voice recognition,

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Dragon NaturallySpeaking
gives us an option to train it.

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So let's begin.

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"Wisdom pursues me,
but I am faster"

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a phrase written
on a Spanish university desk.

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"Nothing is so stupid as to vanquish;
the real glory is to convince."

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Victor Hugo.

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One of the most useful tools
that speech recognition software provides,

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especially at first,
is its support feature.

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Once you install it, it takes you

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on a walkthrough
of the Dragon Speaking software

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that helps you see
all the different configuration options

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and clears up any doubts.

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And for new users, it is very advisable
to read this help page carefully.

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Dragon allows you
to create different profiles,

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meaning not only can I use
this speech-recognition system,

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but also the people around me,
which can be much more productive.

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Now I am going to start
the speech-recognition system

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to write a document.

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I have opened the Word processor
and turned it on.

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"Dear Margarita, comma."

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"Everything’s going great."
"Start new line."

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"We are..."

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"Undo."

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With this command,
I delete the previous word.

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"Go to sleep."

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With this command,
I tell the speech-recognition system

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to stop recognising my voice

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so that I can speak
to the person next to me.

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This is useful when we want
to write an acronym

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or add a word that does not appear
in the Spanish vocabulary.

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We will activate
the spelling command: "Spell."

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O...

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N...

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U.

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A use case contains several elements.

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On one hand, the use cases themselves

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consist of a sequence of actions
and possible variants of these

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between the system and the actors.

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And then the actors,
the people or sets of roles

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performed by users
when they interact with the use cases.

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In our case, we have several actions,

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for example, requesting help to learn
how to use the system;

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selecting one of the users
configured to use the system;

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training the system so that it
recognises my voice better over time;

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activating the speech-recognition system
to dictate or edit a text;

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and deactivating speech recognition.

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The type of user we are talking about
is the client, the end user:

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 the person who uses
the speech recogniser and the text editor.

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But there might be
other roles or actors,

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for example, an installer,
the person who may assist a user

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to sell them the product,
install it, or repair it.

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There are many roles
concerning ICT products.

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The parts of the use case
are the following.

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On one hand, the diagram,
the one we have just seen,

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a UML diagram,

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and on the other hand,
the description of the use case.

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In that description of the use case,

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we provide
slightly more complete information

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that is not included
in the diagram,

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such as the general description
of the use case.

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Here we see that the user can,
in general, request help,

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configure the user,
train the system,

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and use voice recognition
to edit texts.

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The version, the date,
which actors participate in the use case,

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and then we can include
a brief description

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 to define
the basic course of action,

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that is, the steps
that are necessary

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to provide this set of functions
that our system offers. 

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There may be an alternative course.

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It may happen
that this basic course of action

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suffers a small modification
on some occasions.

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It is also necessary to state
a series of preconditions,

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what we assume
has happened beforehand,

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so that this use case can take place.

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In our case, in which the user
is using the voice-recognition system,

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we say that we assume that the user
has approached the computer,

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that it is switched on,

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that the voice-recognition
and word-processing programmes

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have been previously installed
and executed,

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there is a microphone
that is correctly installed,

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 connected to the sound card,

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and that the sound card is configured

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so that the microphone signal
reaches the computer properly

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and the voice recogniser
can do its job.

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There may also be
a series of postconditions,

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conditions that arise
after this use case ends

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and which may in turn
become preconditions

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for another use case to take place.

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Two tools can help us generate
our UML use-case diagrams:

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extends and include.

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"Include" is used to add a sub-function
within a step of a use case.

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We are talking about a subset
of the functionality

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established
by that more general use case.

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In the video we have just seen,

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we could describe "Edit text"
as a sequence or iteration

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of "Enter paragraph",
"Start new line", and "Undo".

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On the other hand,
we have "Extends".

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"Extends" allows us
to add a sub-function

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that does not always occur,
only occasionally,

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in exceptional situations.

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For example, spelling a word
when entering text.

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We only do that when, for instance,

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that word is unknown
to our voice recognition software.

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Let us stop for a moment
to reflect on all this.

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Let us remember that "Edit text"
was a step within a previous use case,

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the general one,

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but it has acquired
a complexity of its own

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 that makes it deserving
of creating a new use case.

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To create this use case,
we will generate a specific table

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in which we will record
a description,

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the basic course of action,
preconditions, etc.

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Well, as the saying goes, everyone
has their own way of doing things,

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and there are multiple ways
of defining a task through use cases.

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The important thing is
that whichever we choose,

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 the system’s functionality
is described fully and coherently

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with the objective
of preparing user requirements.

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For example,
here we have our user,

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who, in order to edit texts,

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we can think
of dividing it into entering words,

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entering punctuation marks,
starting a new line, and undo,

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another decomposition
of functionality,

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but one
that can still serve our purpose.

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In summary, we can say that we utilise
use cases to describe functionality.

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It is important to emphasise

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that we do not include aspects
of accessibility or usability.

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A single use case
should generally apply

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to two people
with different accessibility needs,

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 because it refers exclusively
to the system’s functionality.

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Furthermore, we have seen
that the elements of the use case

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are the use cases themselves
and the actors.

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We have also seen that use cases
consist of a UML diagram

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and a textual description

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that provides some information
not contained in the UML diagram.

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We have also seen the use
of "include" and "extends".

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And that is all.

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Here we finish this video
on developing use cases

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as part of user requirements.

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Until the next video.