Universal naming - UAN and UAL

Universal naming allows actors to become universal actors. Universal actors have the ability of migration, while anonymous actors don't. Service actors are a special kind of universal actors, which grant universally accessing privileges to every actor and never get collected by actor garbage collector.

Every universal actor has a Universal Actor Name (UAN), and a Universal Actor Locator (UAL). The UAN is a unique name that identifies the actor through its lifetime. The UAL represents the location where the actor is currently running. While the UAN never changes throughout the lifetime of a universal actor, its UAL changes as it migrates from one location to another. The format of UAN and UAL follow the URI syntax. They are similar in format to a URL (see Table 4.1).

Table 4.1: UAL and UAN.

TYPE	EXAMPLE
URL	http://www.cs.rpi.edu/wwc/
UAN	uan://io.wcl.cs.rpi.edu:3000/myName
UAL	rmsp://io.wcl.cs.rpi.edu:4000/myLocator

UAN: The first item of the UAN specifies the name of the protocol used; the second item specifies the name and port number of the machine where the Naming Server resides. This name is usually a name that can be decoded by a domain name server. You can also use the IP of the machine. But this is a practice that should be avoided. The last item specifies the name of the actor. If a port number is not specified, the default port number (3030) of the name server is used.

UAL: The first item specifies the protocol used for remote message sending. The second item indicates the theater's machine name and port number. If no port is indicated, a random port is used. The last part specifies the location name of the actor in the given theater.

SALSA naming scheme has been designed in such a way to satisfy the following requirements:

• Platform independence: names should appear coherent on all nodes independent of the underlying architecture.
• Scalability of name space management
• Transparent actor migration
• Openness by allowing unanticipated actor reference creation and protocols that provide access through names
• Both human and computer readability.