VOV: What are sets?

In RTDA VOV technology, a set is an unordered collection of objects. An object may only appear once in a set, but may be a member of more than one set. There are four kinds of sets:

  • system sets
  • enumerated sets
  • selection-rule sets
  • smart sets
The system sets have names beginning with system, for example  system:jobs contains all jobs in the flow. These sets may not be forgotten, and their members are maintained automatically by vovserver.

The enumerated sets contain a fixed collection of objects. If an object is deleted from the flow, it is removed from the set.

The selection-rule sets are defined by an expression. The contents of the set may vary depending on when the selection rule is evaluated.  For example, such a rule might be 'isjob status==FAILED'.  This set could be empty if evaluated at a time when there are no failed jobs.

The smart sets are like a selection-rule set, except that its contents are automatically maintained by the vovserver, continuously evaluating the selection rule as objects are created and forgotten. Because this imposes a computational load on the vovserver, the number of smart sets is controlled by a system parameter, and such sets should be used sparingly.

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