Scope of interface and standard identifiers
Programs or units containing uses clauses have access to identifiers belonging to the interface parts of the units in those uses clauses.
Each unit in a uses clause imposes a new scope that encloses the remaining units used and the program or unit containing the uses clause.
The first unit in a uses clause represents the outermost scope, the last unit represents the innermost scope.
If two or more units declare the same identifier, an unqualified reference to the identifier will select the instance declared by the last unit in the uses clause.