Parasuraman (1997) pointed out that

Parasuraman (1997) pointed out
that driven factors of customer cognitive value included
product quality, service quality and price factor. This
research achievement has received universal recognition
from the academia. Among the aforementioned three
factors, service quality is more difficult to be duplicated bycompetitors than product quality and price. Therefore,
how to present the optimal service quality becomes the
source of sustainable competitive advantage of an enter-
prise. Other scholars made supplement to the afore-
mentioned, for example, the maintenance of brand equity
and customer relationship (Ravald and Grönroos, 1996)
and so on.