keywords-interface

Interfaces are like classes with only declarations of procedures and properties. They don't provide any data storage or other implementation. Classes associate themselves with an interface with the implements keyword. They can implement as many interfaces as needed. All interface methods are implicitly public. If this interface isn't extending any other interfaces, the extends clause can be omitted. Interfaces use the extends keyword to extend other interfaces.

\interface\ identifier
  [extends BaseInterfaceList]
  ' Declare procedures as needed, but without any implementations