Abstract
This paper is a part of the document which my colleagues and I prepared for the National Air
Traffic control System (NATS), UK, to highlight the problem areas involved in the design,
development, implementation, upgrade and management of safety critical distributed systems.
NATS monitors and decides the flight paths of civilian aircrafts in the British air space. Its
operations are conducted centrally from West Drayton, and its engineers are reported to have
stated that the strain on the central system grows inexorably, stretched to the limits during busy
periods. A way to address these concerns is to scale up the system through decentralisation and
maximal re-use of the existing legacy software. In this approach, the existing (central) system
needs to be deployed as subsystems in many, geographically-apart centres; each subsystem will
be responsible for a well-defined sub-domain of the over-all air-space and must frequently
coordinate its activities with other subsystems so that certain services it provides are correct and
consistent at the system level. The core requirement here is to have certain distributed services,
which support such an expansion in a reliable and responsive manner. The services we identify
here are generic enough to support a wide range of applications, say, from constructing global
auction services over the Internet to managing replicated database servers on an institutional
network.
The focus of this paper is to highlight how such services can be constructed. We indicate the
various models available and identify their strengths and weaknesses, thus exposing the design
options available to a system builder. We expound on a particular model by presenting the
features of the NewTop system that is designed in Newcastle and implemented in a CORBA
compliant manner.
Building Responsive and Reliable Distributed Services: Models and Design Options
In Workshop on CORBA Based Real-Time Fault-Tolerant Systems for Industrial Applications (CORFIA 2001), Bangalore, India, 6-7 April 2001
Centre for Development of Advanced Computing, Bangalore, 2001
[Abstract]