Re: Object-Oriented Systems and Realtime

From: (David B Stewart)
Organization: The Robotics Institute, Carnegie Mellon University
Date: Mon, 11 Oct 1993 16:51:19 GMT

In article <>,
Chris Zimmermann <> wrote:
>Hi community:
>What is the state of the art concerning real time in 
>object-oriented systems (if any)? By this, I mean the
>marriage of more or less traditional real time systems
>(including systems concerned with "soft" real time aspects
>like multimedia) with the OO paradigm.

We've done significant work in that area.  Check out the following tech

D. B. Stewart, R. A. Volpe, and P. K. Khosla, "Design of Dynamically
    Reconfigurable Real-Time Software using Port-Based Objects," 
    Carnegie Mellon University Tech Report #CMU-RI-TR-93-11, July 1993.

	Abstract: The current development of applications for sensor-based
	robotic and automation (R&A) systems is typically a `one-of-a-kind'
	process, where most software is developed from scratch, even though
	much of the code is similar to code written for other applications.
	The cost of these systems can be drastically reduced and the capability
	of these systems improved by providing a suitable software framework
	for all R&A sys tems. We describe a novel software framework, based on
	the notion of dynamically reconfigurable software for sensor-based
	control systems. Tools to support the implementation of this framework
	have been built into the Chimera 3.0 Real-Time Operating System. The
	framework provides for the systematic development and predictable
	execution of flexible R&A applications while maintaining the ability to
	reuse code from previous applications. It combines object-oriented
	design of software with port-automaton design of digital control
	systems. A control module is an instance of a class of port-based
	objects. A task set is formed by integrating objects from a module
	library to form a specific configuration. An implementation using
	global state variables for the automatic integration of port-based
	objects is presented. A control subsystem is a collection of jobs
	which are executed one at a time, and can be programmed by a user.
	Multiple control subsystems can execute in parallel, and operate
	either independently or cooperatively. One of the fundamental concepts
	of reconfigurable software design is that modules are developed
	independent of the target hardware. Our framework defines classes of
	reconfigurable device driver objects for proving hardware independence
	to I/O devices, sensors, actuators, and special purpose processors.
	Hardware independent real-time communication mechanisms for
	inter-subsystem communication are also described. Along with providing
	a foundation for design of dynamically reconfigurable real-time
	software, we are also developing many modules for the control module,
	device driver, and subroutine libraries. As the libraries continue to
	grow, they will form the basis of code that can eventually be used by
	future R&A applications. There will no longer be a need for developing
	software from scratch for new applications, since many required modules
	will already be available in one of the libraries.  

This report is available via anonymous FTP as follows:

	% ftp IUS4.IUS.CS.CMU.EDU	(
	Name:       anonymous
	Password:   yourname@yourmachine
	ftp> binary
	ftp> cd /usr/chimera/public
	ftp> get
	ftp> quit
	% uncompress
	% lpr	(must be a postscript printer)

For more information, 'finger'.

>50 Ada-9x (compiler, GNU)
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