| # Section 7.1.1: $OB |

###### abstract class $OB

#### Formal Definitions

This abstract class defines a state component which is a set of all instantiations of objects of any class in addition to the vdm model types used wherever this class name is used. In this particular instance the sub-typing test is vacuously true. Note also that SAME has to be an instantiated class, not an abstract one.

types
SAME = object_type ;
$OB = set of object_type
state
objects : $OB
inv obj_types ==
forall obj in set obj_types sub_type($OB,obj)

NOTE | See the important note about vdm state in the notes on vdm-sl usage in this specification.

This class is the abstract root class for the Sather language. All classes, irrespective of whether they inherit from other abstractions, implicitly sub-type from this class.

This class defines no features.

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Comments or enquiries should be made to Keith Hopper. Page last modified: Thursday, 18 May 2000. |