Extractor of contacts' data from result.
An encapsulation of the signal that targets a subsystem's internal contact.
This contact is used to process answers of internal system.
This contact is used to process signals of internal system.
This contact is used to process signals of internal system.
In asynchronous execution the resulting signal should come at the same level of "call stack". However as far as we usually get the signal asynchronously it is processed at top level. So in order to run it in inside the subsystem, we package asynchronous result into Signal(SubsystemSpecialContact, SubsystemDirectSignal( name, actual resulting signal))
Create a contact with the given name.
Create a contact with the given name.
One may use notation (contact -> data) to represent a signal