TUNNEL INSTALLATIONS - The Westerschelde Tunnel: Approaching Limits - page 238

Architecture and structure of the system
System architecture concerns the fundamental organisation of a system as
this is given shape by its components, their mutual cohesion and the cohe-
sion with the environment, as well as the principles which act as a guide for
the design and evolution. In order to be able to develop an EM system from
the schedule of requirements (desires), the desired functionality must con-
tinually be subdivided into small uncomplicated functional units.This division
is also determinative for the realization of a function in hardware, software
or both.The architectural approach is so important, because it not only sup-
ports a cohesive concept of the system to be realized from the very start, but
also provides guidance and sets limiting conditions to design decisions. A
recognisable technical structure has gradually been created from within the
architecture of the Westerschelde Tunnel system. The architecture as well as
the system structure are (contextually) the most important reference frame-
works in the setting up and elaboration of a functioning testing programme.

Technical structure
Westerschelde Tunnel
system

Fig. 15.12

Application/functionality of subsystems in the control and operating systems (181 and 189)

Basic functions of control and operating systems (182, 183, 184) (firmware/communication drivers)

Hardware of control and operating systems (182, 183, 184)

Fire
extinguishing
(150)

Intercom,
Public address
(163/164)

Traffic
(141,
142)

Drainage,
ventilation
(130, 135)

Building
security
(172)

Fire alarm
detection
(174)

Energy
(110)

Lighting
(120)

Video
(161)

HF
(162)

Telephone
(165)

VRIs
(145)

Transmission system (185)

Functioning testing programme
The development of a functioning testing programme is of importance in
order to be able to determine if the EM systems comply with the schedule of
requirements. A functioning testing programme is a trajectory which
encompasses multiple steps and which runs 'bottom up', contradictory to a
design trajectory: it starts with small independently functioning parts of
which it is determined, by means of testing or by means of a 'document
review', or by means of a combination of both, whether the parts comply
with the requirements. Gradually these units become larger and more com-
plicated until eventually the entire integral system is tested. Combined with
this method, the components are firstly tested at the factory level and even-
tually in their full composition, preferably in a 'test bed' first and then at the
final location. Although it is a managed approach, it should not be forgotten
that a component may comply with the requirements, while the functioning
of the composition of components is not acceptable. For acceptance in this,
in principle the requirements on the higher level apply. A ventilator can for
example, function in accordance with the standard, but when it appears that
the whole ventilation system does not work because the operating software
is inadequate, this means that the entire system cannot be accepted. In
redesigning, it is then possible that other ventilators must be applied.
To summarize, the scope of the functioning testing programme encompasses:
- the determining of the proper working per component;

- the determining of the proper working per system;

- the determining of the proper working of the cohesive system.