SERG REPORT - Deriving Real-Time Monitors from System Requirements Documentation

• Subject: SERG REPORT - Deriving Real-Time Monitors from System Requirements Documentation
• From: Doris Burns <burns@raid.cas.mcmaster.ca>
• Date: Mon, 24 Jan 2000 10:24:09 -0500 (EST)

January 24, 2000

Dear Sir/Madame:

Below is an abstract for SERG Report 383 which was recently 
completed by McMaster University's Software Engineering Group.  

Our web address for downloading reports is:

http://www.crl.mcmaster.ca/SERG/serg.publications.html

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Yours truly,
Doris Burns

				SERG Report 383
	Deriving Real-Time Monitors from System Requirements Documentation
	           		Dr. Dennis Peters

When designing safety- or mission-critical real-time systems,
a specification of the required behaviour of the system should be
produced and reviewed by domain experts. Also, after the system has
been implemented, it should be thoroughly tested to ensure that it
behaves correctly.  This, however, can be difficult if the requirements
are complex or involve strict time constraints. A monitor is a system
that observes the behaviour of a target system and reports if that
behaviour is consistent with the requirements. Such a monitor can be
used as an oracle during testing or as a supervisor during operation.
This thesis presents a technique and tool for generating software for
such a monitor from a system requirements document.

A system requirements documentation technique, based on [102], is
presented, in which the required system behaviour is described in terms
of the environmental quantities that the system is required to observe and
control, which are modelled as functions of time. The relevant history of
these quantities is abstracted as the initial conditions and a sequence
of events. The required value of all controlled quantities is specified,
possibly using modes---equivalence classes of histories---to simplify
the presentation.  Deviations from the ideal behaviour are described
using either tolerance or accuracy functions.

The monitor will be affected by the limitations of the devices it uses
to observe the environmental quantities, resulting in the potential for
false negative or positive reports. The conditions under which these
occur are discussed.

The  generation of monitor software from the requirements documentation
for a realistic system is presented. This monitor is used to test an
implementation of the system, and is able to detect errors in the
behaviour that were not detected by previous testing. For this example
the time required for the monitor software to evaluate the behaviour is
less than the interval between events.

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