AN ARCHITECTURAL PATTERN FOR REAL-TIME CONTROL SOFTWARE

Bran Selic
ObjecTime Limited
340 March Rd.
Kanata, Ontario, CANADA 
K2K 2E4

e-mail: bran@objectime.com
phone: (613) 591-3435
fax: (613) 591-3784

ABSTRACT

In this paper, we introduce a high-level design pattern that can be
applied to a broad class of real-time systems. This pattern, which we
call Recursive Control, provides a systematic method for dealing with
what are traditionally considered ancillary software functions (system
start up and shut down, failure detection and recovery, on-line
maintenance, etc.). In many large systems, such functions represent as
much as 80% of all the code written yet they are still given lower
priority in system design. The result are systems that are difficult to
control and evolve.

The Recursive Control pattern implements a clear separation between the
control aspects and the service-providing aspects of a real-time system
allowing each to be defined and modified independently. The pattern can
be applied recursively which means that it is applicable across a wide
range of levels and scopes, starting from the highest system
architectural level down to individual components.