Consider the E-R diagram in Figure 8.25. Are all three relationships—Holds, Goes_on, and Transports necessary (i.e., can one of these be deduced from the other two)? Are there reasonable assumptions that make all three relationships necessary? If so, what are these assumptions?

Figure 8.25

Transcribed Image Text:

AGENT CONSIGNMENT CONSIGNMENT Is responsible_for May_contain " Consignment_Number $ Value Agent_ID Consignment_Number $ Value Holds Transports VESSEL Vessel ID Country_of_ Registry Goes_on VOYAGE Voyage_ID Tonnage