When your rule condition or filter are not defined by a range of values, you might have tried use a series of test and logical OR operations to describe the test. For example, entity1.attribute1='This' or entity1.attribute1='That' or entity1.attribute1='TheOther' is long, and could evolve into a very long expression. You can eliminate the use of the long form of enumeration literals by using the in operator's list format to reduce that filter or condition expression to entity1.attribute1 in {'This','That','TheOther'}.
You can go a step further by defining enumerated lists to define even more brisk expressions, where the labels that you choose are abbreviations for the full names. For example, Regions.state in {MA,NH,VT,CT,RI,ME} to qualify only US New England states.
