Annotating objects for transport to other worlds
Ungar, David
Abstract
In Self 4.0, people write programs by directly constructing webs of objects in a larger world of objects. But in order to save or share these programs, the objects must be moved to other worlds. However, a concrete, directly constructed program is incomplete, in particular missing five items of information: which module to use, whether to transport an actual value or a counterfactuaI initial value, whether to create a new object in the new world or to refer to an existing one, whether an object is immutable with respect to transportation, and whether an object should be created by a low-level, concrete expression or an abstract, type-specific expression. In Self 4.0, the programmer records this extra information in annotations and attributes. Any system that saves directly constructed programs will have to supply this missing information somehow.