Assume that data are maintained on airports around the country for a company that offers a flight chartering service for college basketball teams. They gather information from a wide variety of sources, but have had considerable difficulty in the past obtaining data on runway surfaces at airports located in small college towns. Company pilots need access to this information when they must land either at airports such as these or in occasional emergencies, when they must land at other small airports that are not located in college towns. As a result, as shown here, they have created a RUNWAY_SURFACE entity type separate from a RUNWAY entity type.

a. What does the cardinality ratio and participation constraint suggest about some airport runways in the Consists_of relationship?
b. How might the Presentation Layer ER diagram be revised to make the relationship between an airport runway and runway surface more efficient?

Runway length Rurwav no Surface type Aimort d Airport name Runway no Runway width Consists o RUNWAY UI SURFACE AIRPORT Contains RUNWAY Surface condition