We now turn to the library application. For convenience, we divide the ORM schema into four subject
areas: membership, loan, book, and book shipment. Figure 7 shows the main aspects of the membership
subschema. The reference mode “Id” for Person indicates that each person has a value-based identifier,
called PersonId, used in human communication. Each person also has a name, not necessarily unique. A
library year is a calendar year, at some time during which the library was in operation. The reference mode
“CE” denotes “Common Era”, indicating calendar years are based on the Gregorian calendar.
The association Membership covers Year is objectified as the entity type AnnualMembership. Its
association with FeeType indicates whether or not a given member has been granted a reduced membership
fee for a given year. If desired, a derived fact type may be added to infer the fee paid for a given annual
membership, based on the fee type and the membership fee of that type for the given year. For simplicity
we assume that a member pays the full annual fee regardless of when he/she began or renewed the annual
membership. In practice, it would be more usual to apply a pro-rata fee or extend the membership to a year
after the date paid.
We now turn to the library application. For convenience, we divide the ORM schema into four subject
areas: membership, loan, book, and book shipment. Figure 7 shows the main aspects of the membership
subschema. The reference mode “Id” for Person indicates that each person has a value-based identifier,
called PersonId, used in human communication. Each person also has a name, not necessarily unique. A
library year is a calendar year, at some time during which the library was in operation. The reference mode
“CE” denotes “Common Era”, indicating calendar years are based on the Gregorian calendar.
The association Membership covers Year is objectified as the entity type AnnualMembership. Its
association with FeeType indicates whether or not a given member has been granted a reduced membership
fee for a given year. If desired, a derived fact type may be added to infer the fee paid for a given annual
membership, based on the fee type and the membership fee of that type for the given year. For simplicity
we assume that a member pays the full annual fee regardless of when he/she began or renewed the annual
membership. In practice, it would be more usual to apply a pro-rata fee or extend the membership to a year
after the date paid.
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