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3.5 Smart Objects, Smart Applications 179
The smart application technology allows the definition of multiple rule
sets for a smart object. Thus, it is possible to configure multiple application
modules and interconnect them by logical links. Smart applications can be
realized within a node or even distributed over a whole sensor network.
In order to make the implementation of smart applications easier for the
user, a graphical development environment allows defining rule sets with
the help of jigsaw puzzle pieces Figure 3.11. The editor provides SAL elements
— such as events, instructions, variables and common language components
— which can be connected to a jigsaw puzzle. The backend generates the
corresponding SAL code and the user level is arranged on a higher abstraction
layer. The following Figure 3.12 shows the complete workflow of the smart
application development.
The SAL source code, generated by the graphical editor, is compiled to
an optimized and highly compressed byte code. Due to the small size of the
resulting data, a complete configuration can be sent via the radio interface of
the smart object. It is also possible to send multiple of these configuration
sets and store them on a persistent memory as application profiles and switch
between them on demand.
After receiving a configuration, the smart application manager configures
all corresponding modules on the node regarding to the rules. It starts the
components in sequence of their application priority. The application is then
ready to operate. A reconfiguration can be done at any time and with any
Fig. 3.11 Service oriented approach — left and Smart application approach — right.