The document discusses the service system design matrix and the role of customers in service systems. The service system design matrix defines the relationship between sales opportunities and production efficiency based on the level of human interaction. It establishes the relationship between the degree of customer contact, sales opportunities, and production efficiency. Customers are considered "partial employees" as they contribute resources to the production process. The level of customer participation can range from quasi-services with low contact to pure services with high contact. Service blueprinting is also discussed as a tool used to map customer touchpoints and the internal processes involved in service delivery.