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Diagramas de Secuencia UML
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Hello, I hope you are doing
very well. The topic for today is
sequence diagrams. Well, what are they
and what are they for? Basically,
sequence diagrams are a type of
diagram that belongs to the ML library.
ML is a set of diagrams that
make up this library. It is the
unified modeling language that has been defined internationally.
internationally.
Unified Model Languages, for its acronym in English.
English.
There are many diagrams that belong
to this library, among them are
use case diagrams,
flow diagrams, process diagrams, and sequence diagrams.
Specifically, what are they for? Well, it
serves to illustrate the sequence, as
its name suggests, in the interaction between
objects. See that this concept is very important here
since we mentioned the
word objects and by object, well, as
you know, at the programming level,
anything tangible or intangible that
has characteristics and hopefully methods or
interfaces with which it communicates with
the outside world
can be considered an object in
a given process, no matter the
type of process we are in. Whether it is
for a billing system, an
order delivery system, for
example, a registration system, we are going to
have different objects that interact
in this process and we can illustrate the
average. the sequence diagram
also illustrates the messages through which
these objects interact it
is very important that there is an
interaction for these objects to be
part of the sequence diagram and
basically the idea is to know in what
order each of them interacts
who comes first who comes next who
made this request who received it what
happened after this and establish a
timeline that allows us to
basically know the sequence of the process
what are the visual elements that
compose it very important it is always
important to know specifically what
each of the elements of the
diagram means and to respect what the standard
defines for example we have the
object avia line the rectangle at the
top is the object then there we
could put the name of a
specific object that is going to interact in
our system the sequence diagram is
read from top to bottom the events
happen in that order what is
above what is first and what
is below what is
after the lifeline is that
dotted vertical line that basically defines
the time in which this object
interacts with other objects by sending
messages or communicating in the sequence diagram
we have the activation that activation
is basically when some
event or action happens within an
object and is placed inside or on the
life line of the object since this way we will
see an example where we can
show how an activation is placed the
activation is a very important element
since other elements are also reflected in it
such as the sending of
messages the sending of messages is
represented by a line with an
arrow this arrow can be to the
right or it can be to the left it
leaves the life line of an object and
must reach the life line of another object
object
in addition
a very short but very specific phrase must be placed on the line
that basically describes what is the
message that the first object is sending
to the second object as I was
saying it can be to the right or
to the left
also these messages can be auto
messages what does an auto message mean
for example it is widely used
when we make a query to a
database let's suppose that here a
message comes from left to right it reaches
the activation of the database and the
database performs the auto query or
performs an auto process in which it
consults itself about the request
that was made to it and then returns the
message now very well when we have
messages that only go from one object to
another and then to another and then another and they do not
have a specific evolution, that is,
they were not sent specifically to be
returned, so they are simply
messages, but when a specific message is sent
from which a
return is expected, it is responded with this type of
arrow which is a line with an arrow but
the dotted line.
Now in the same way, this dotted line
with the arrow can go to the
left or it can go to the right,
but it must always go as a response
to the message for which it is fulfilling its
function, for example, a query is made
to the database, the database
carries out its self-processing or its self-
message and then comes a
return message that would be with the
dotted line, ok, let's see an example
continuing with the example of the
enrollment system in which a student
needs to enroll in a course or a
set of courses, we could see it
this way, we have the following
actors, which would be the student, a
registration person, the system, and the
database. Now, very well, this is an
example in which we have these actors
or these objects, we could have more
objects or fewer objects, ok, so let's
remember that the sequence diagram
is read from top to bottom.
The first activation we have here is
by part of the registry which is the activation
activation
that is above the others
then we begin to read it there
then the person in charge of digital registration
the courses to publish where they digitalize them
in the system ok so now what does
the system do the system receives that message
and generates an activation where the
system sends a request to the database to
store the
course information then the database
receives that message stores it and then
confirms the storage see that here I
have an example in which it sent a
message from the right and sent a
return to the left it could be
the other way around also it depends on the order in which
the objects are that does not alter the product
product
now the system at the same time sends
a publication confirmation to the
person in charge of registration and see that
here at this moment registration has no
interaction with the student
simply registration interacts with the
system and with the database and the
student enters into action or enters into
function after what the
registration officer did however between
them there was no direct interaction
for example registration did not write to the
student to tell him that he will
register at this moment you see or
anything like that between them there was no
direct communication in this example
but as we read vertically top
down then we know that
after the registration confirmation the
student continues with this activation
that we have here in the
student activation he now what he does is that he
consults the available courses where in
the system the system consults based
on the business rules which are the
business rules in this case it is an
enrollment system the business rules
that for example the course is available
that the student meets the requirements
requirements
that the schedules will not conflict that it
belongs to that career that it is in the
appropriate semester etcetera those are
the business rules
now we have an execution of an auto
query see that here it says
query execution and it is an auto message which is one
of the examples that we had in the
previous slide where the
database generates its own query as well
and then returns the list of courses
unit is a return message
reaches the system and what the system
does is that it displays the list of
available courses for the student receives
that message the student and then takes
an activation or generates an activation
where now it says that he selects
the courses to enroll where in the
system the system makes a request
to store the enrollment in the
database The database confirms the
storage, the system confirms the
enrollment of the student and the
sequence diagram is completed. We read it
from top to bottom and we were able to read and
understand the sequence of how
the objects that are the
student registration system and
database interact through the lifeline of
each of the subjects and how
messages like these are sent in returns, how
requests are made and even auto
messages in this process.
Very well, I hope it was very
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