The Extent of Objects and Entities

  Each object, attribute or local entity of a method has a lifetime or extent, i.e. that part of the program execution during which it may be used.

The extent of an entity locally declared in a block of a method begins by executing its declaration and ends with the termination of the block. This rule also applies to method bodies including the declarations resulting from parameter transmissions.

The extent of all other quantities extends indefinitely from the time of their creation. They are created as follows:

• A shared attribute is created prior to the call of the procedure main.
• A non-shared attribute of a class is created whenever an object belonging to this class is created.
• An object belonging to a class C is created whenever a type constructor or is evaluated where a denotes an object of type C.

Note: Indefinite extent does not imply indefinite accessibility to an object. As soon as all the variables or constants which had a reference to a global object as their value cease to exist or have changed their value or have become inaccessible themselves, it is no longer possible to access such a global object or any of its features. Hence SATHER-K should be implemented using a garbage collector since global objects are never automatically or explicitly deleted.