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4.5. *EVENT MACHINE
The Event Machine , based on user’s configuration decides what,
where and when to send a report and/or execute an action, but
it is not all of the configuration needed by the unit. When
the user starts configuring the Event Machine , it is assumed that
he has already defined the Destination Addresses an their corre-
sponding Destination Points as described on the previous sections
of this chapter. Enabling the unit on the GSM/GPRS network is
also required.
Note:
4.5.1 Triggers
A trigger is determinated with the logical combination of several sit-
uations (also called signals). A logical combination is basically an
equation (specifically: a boolean equation) that combines signals (sit-
uations) with the logical operators
AND
,
OR
and
NOT
.
Combining situations with operators: Example
An e-track
TM
traveling at or over 60mph is a situation, let’s call it
situation
S
. This situation may be true or may be false , there are no
other possibilities. These kind of situations that can only take two
possible values,
true or false , are said to be of boolean nature. Let’s
add another
boolean
situation: An unit located within some cities’
perimeter. This again is a two-value situation. Let’s call it P.
How can we combine these two situations to create a third complex
situation ?. We can do so with logical operators. For example, let’s
create a third situation C that is only true when the other two situa-
tions are also true. For this we use the
AND
operator in the following
form:
C = S AND P
Now, every time S and P are both true at the same time, C is going
to be true too. Whenever S or P become false, C will become false.
The situation we just created (named C) is useful for detecting an
speed limit violation within a cities’ perimeter. With C we specify
that we are interesting not only on detecting a general speed violation
but an specific speed limit for an specific city boundary. Note that a
cities’ perimeter is just an example: We could have specified a road
or a small neighborhood.
You can create simple triggers which go off whenever a single specific
situation occurs, like when
e-track
TM
’s button is pressed. Or you
can construct more complex triggers by combining situations with
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