Information Technology Reference
In-Depth Information
Perceptual
Reference
Point
Interworking
Reference
Point
Interchange
Reference
Point
Interworking
Reference
Point
Programmatic Reference Point
(within software)
FIGURE 8.3: Conformance points for the mobile phone.
may be required to generate a pop-up message when it detects unusual event
traces. Checking that this actually happens must be performed at a perceptual
reference point.
An interchange reference point is a point where some portable medium
is read or written, and this process can be checked by observing the state of
the medium before and after a known series of operations. For example, the
specification might state that, in certain circumstances, configuration details
on a removable SD memory card are updated; the tester can remove this card
and see if the change has in fact been recorded. Or a customer's conrmation
of order information may be written onto a smartcard, and subsequently this
recorded copy can be checked for consistency with the system's state.
To illustrate these ideas, consider the provision of a phone tester by a sub-
contractor (see figure 8.3). A test SIM is loaded into the repaired phone, which
is then connected to the tester, using an external interface provided by the
handset manufacturer. A software harness is loaded into the phone's memory.
The tester orchestrates a series of tests, in which the functions of the phone
are exercised, including reading and writing the SIM, presenting patterns on
the phone's display and exercising the wireless receiver and transmitter. At
the end of the test, the SIM is plugged into the tester and its contents checked.
In this scenario, the tester is connected at an interworking reference point;
the wireless interface provides another interworking reference point. The load-
ing and running of the test software depend on there being a programmatic
reference point at which a particular set of operating system services are avail-
able. The checking of displayed patterns takes place at a perceptual reference
point, and finally the SIM checks require an interchange reference point.
