TitleThe IBM SOM metaclass
CreditsDanforth Scott, H.
PublisherUniversity Video Communications
DescriptionFrom University Video Communications' catalog:
"In SOM, the IBM System Object Model, a class is a run-time object that defines the behavior of its instances. Because classes are objects, their behavior is defined by other classes (called meta-classes). The first part describes the unique facilities provided by SOM to support metaclass programming: SOM-derived metaclasses combine programmer-defined metaclasses to guarantee correct polymorphic behavior for classes, and metaclass cooperation prevents interference between metaclasses that are combined into a SOM-derived metaclass. The second part describes the use of these facilities to implement composable Before/After Metaclasses. A before/after metaclass ensures that invocation of methods is preceded by execution of a "before method" and followed by execution of an "after method." Composibility ensures that different before/after behaviors will be automatically combined in an appropriate fashion by SOM-derived metaclasses."