Information Technology Reference
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The character sequences <= and >= are used to
describe the respective relations.
As the next part, the event handlers are added
to the binary event specification, which are con-
secutively listed and separated by comma. Fi-
nally, the binary event specification is completed
by adding the remaining elements containing the
phenomenon constraints, which are the execution
element and the dimension element. Phenomenon
constraints consist of their short identifiers, fol-
lowed by the symbolized relation attribute and
one or two constants. These constraints are de-
scribed in infix notation and are evaluated on the
sensor nodes by string matching operations ac-
cording to the following regular expression:
from 710 Bytes plus white-spaces down to 56 Bytes
provided as binary event specification. Figure 6
displays the respective binary event specification.
Deployment on Sensor Nodes as
Event Decision Tree (EDT)
This section presents how sensor nodes are au-
tonomously configured according to binary event
specifications. It describes the conversion of
binary event specifications into their processable
form as Event Decision Tree (EDT). The EDT
enables every node to self-divide configuration
queries according to its resources and to execute
the complete event evaluation process. Unlike in
other approaches, nodes are not only used as data
sources for sensing and distributing raw data. In
fact, every node can independently analyze and
process its sensor readings and come to a final
decision about the existence of a phenomenon.
The EDT is a fully distributed concept that does
not require special nodes for information-fusion
and final evaluation. This is considered mandatory
to prevent from SPoFs, which are naturally arising
if only one or a few nodes are enabled to execute
the complete detection and evaluation process.
Such concept significantly reduces the energy
[A-Za-z]
+
[<|>|=|<=|>=|<>]
{1}
[0-9]
+
([,]
{1}
[0-9]
+
)
{0,1}
Binary event specifications are transmitted as
Byte-Streams to the sensor nodes whereby the base
elements are separated by colons. Adherence to
such strict layout reduces the size of binary event
specifications compared to the event specification
by an average factor greater than ten. For instance,
that downscales the size of the introduced event
specification for fire detection by a factor of 12
Table 2. Conversion table containing event specification elements and respective binary event specifica-
tion elements. Unlisted elements of the event specification need not to be converted. These are implicitly
represented by the fixed-order structure of the binary event specification.
Event specification
Binary event specification
Event specification
Binary event specification
<AND>
&
<PRODUCT>
*
|
/
<OR>
<QUOTIENT>
<NOT>
!
<MODULO>
%
<EQUAL>
=
<TIMEINTERVAL>
I
<GREATER>
>
<CIRCLE>
C
<LESS>
<
<SQUARE>
S
<GREATEROREQUAL>
>=
<BALL>
V
<LESSOREQUAL>
<=
<CUBE>
K
<SUM>
+
<HOPS>
H
<DIFFERENCE>
#
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