A correlation set is declared within a scope, similar to a variable declaration. You can declare both global and local correlation sets.
You can hide a correlation set in an outer scope by declaring a correlation set with an identical name in an inner scope. If you declare the correlation set locally for a scope, it is applicable only to the activities in the scope.
A correlation set can be initiated only once during the lifetime of the scope it belongs to.
A correlation set must be initiated.
After a correlation set is initiated, the values of the properties for a correlation set must be identical for all messages in all operations in the scope.