Opaque data types carry information that the intermediate PSYC routers and tools do not need to understand and make sense of. Since PSYC is by design transparent all content transferred over it can be opaque or unknown. By means of inheritance of methods and variables applications can always make custom extensions in PSYC. Therefore all data in PSYC is opaque until it arrives at the intended destination. We may however be suggesting _opaque as a variable type, should we ever find an unlikely reason to need that.