This classification can be loosely linked to the purposes of testing. For
quality control, fundamental properties are not needed, apparent properties
will usually be acceptable, although functional properties would certainly be
desirable. For predicting service performance, the most suitable properties
would be functional ones. For design data, fundamental properties are really
needed, although considerable help can often be got from functional
properties. For investigating failures, the most useful test will depend on the
individual circumstances but it is unlikely that fundamental methods would
be necessary.