Field Specifications - Database Design for Mere Mortals - page 245

Figure 9.9. Generic field specification for a generic S TATE field
Take note of these particular items.
1. The description is very general, as it should be for this type of specification.
2. The setting of the Display Format physical element is in the form of an instruction.
This demonstrates that you have a great deal of flexibility in the way you set this
element.
3. The Range of Values logical element is appropriately broad.
4. The Comparisons Allowed logical element is set to “Value Expression—Equals”
so that a user can compare S TATE values to some arbitrary two-character alphanu-
meric value.
5. The Operations Allowed logical element is set to “Other Fields—Concatenation”
so that a user can concatenate a given S TATE value to the value of some other al-
phanumeric field.
6. The Operations Allowed logical element is also set to “Value Expres-
sion—Concatenation” so that a user can concatenate a given S TATE value to some
arbitrary alphanumeric value.
This field (and its specification) now serves as a template for all other state fields you
create inthedatabase. Forexample, youcancreate aV END S TATE fieldbasedonthegeneric
S TATE field. You'll define a Replica specification for the V END S TATE field that is based on
the S TATE field's Generic specification. Although the V END S TATE field's Replica specific-
ation draws its initial element settings from the S TATE field's Generic specification, you
can modify any of the Replica specification's element settings so that you can completely
customize them for the V END S TATE field. Figure 9.10 shows the customized Replica field
specifications for the V END S TATE field.