Page 408 - Unleashing the potenti al of the Internet of Things

4 Unleashing the potential of the Internet of Things

Appendix I

Use case of SCN for verification

(This appendix does not form an integral part of this Recommendation.)

I.1 Errors in decisions
The decision-making process in SCN applications includes different activities and can be very
complicated. As a result, there is a whole series of sources of errors in decisions:
– Unreliability of communication channels. Normally, SCN applications intend to make wide
usage of wireless communications which are more error-prone in comparison with wired
communications.
– Distributed calculation model. This model makes it difficult to synchronize all the activities
and to provide all the SCN objects with actual data.
– Not very predictable duration of the decision-making process, due to different delays in
calculations and data transmissions.
– Mobility of actuators and possibility of their usage for different SCN applications. When
this is accompanied by the presence of several software and hardware vendors of actuators,
this feature deprives the system designer of the possibility to test the system thoroughly in
various conditions. Furthermore, when the interaction of the actuator with the SCN
infrastructure is not on a systematic basis, making critical decisions cannot be entrusted
entirely.

– Hardware and software errors.
As a result, control commands given by SCN applications should be analysed in order to ensure that
possible errors do not result in considerable negative consequences. When a control command is
intended for an information actuator, it can be analysed by the human who receives the control
command. When a control command is forwarded to another network by a gateway actuator, the
duty of analysis shifts onto the other network. But when a control command should be carried out
without any direct human intervention to a machine actuator, special measures should be taken to
counteract errors in decisions made by SCN applications.

I.2 Verification
For a machine actuator, there is a set of critical operations which can lead to considerable negative
consequences when carried out in an improper system state. To avoid this, for each critical
operation, a set of rules should be defined, which must be checked before this operation and/or
while the operation is in progress. These rules are called "verification rules". To check the
verification rules, a number of values of different types must be determined:
– Aggregate values, reference values, sensed data obtained in SCN application as part of
normal flow of decision making.
– Aggregate values, reference values, sensed data obtained in SCN application which are
only intended to support verification.
– Sensed data obtained from sensors associated with machine actuators.
– Values obtained upon request from SCN controllers or NGN entities.

394 Rec. ITU-T Y.4250/Y.2222 (04/2013)