Expression Property
Like the DerivedProperty policy, the ExpressionPropertyPolicy defines properties as functions of other properties already in scope. These properties are defined using configuration parameters of the form:
properties.[table-name].[property-name]=[prop-expression]
The right hand side of this definition is a PropExpression
This policy adds new definitions for existing properties already in scope. It also provides a mechanism for adding properties defined using configuration parameters.
The configuration parameter:
registry_list.table-name defines a comma separated list of configuration property registries to be included in scope.
And a property can be added to one of these registries by setting a configuration parameter of the form:
property.registry-name.property-name=type
Because the properties are defined independently of the policy this allows the same properties to be defined in multiple tables and to be accessible from a UsageProducer that includes the multiple tables.
