The five gap model. Parasuraman, Zeithaml & Berry’s (1994) Quality Service Model is a helpful instrument to define the objectives of quality management. It is basically customer-oriented and it helps to explain the co-service process.
According to this model, consumers’ quality assessment will be influenced by a series of five distinct “gaps” in this co-service process. Quality Management Systems must attempt to close the five gaps in the model and to improve the quality of service as experienced by means of comparison between expected and perceived quality after the customer has received the service.