Open Systems and Open Architecture

Peter Henderson

Updated 8th February 2012


An Open System is a modular construction that has been designed in such a way that its modules have precisely defined and publicly owned interfaces, where these interfaces allow independent suppliers to provide improved capability by providing innovative, plug-compatible modules.This modular structure, made from modules with open interfaces, is referred to as an Open Architecture.

The following reports address the issues of Open Systems in general and those of Open Architecture in particular. They are all drafts at this point in time and so are periodically updated. Each document is dated for its most recent revision. Comments can be sent to me at and this page can be referred to as

A Fuzzy measure of Openness - February 2012 (work in progress)
A measure of openness is defined that is based on an estimate of the number of independent companies that make use of an apparently open interface.
Modular Open Systems Architecture - April 2009
The concepts of System Architecture and Open Systems are introduced. The benefits of adopting a relatively formal approach to Architecture description are discussed and the scene set for the method of Architecture Description to be advocated in a later paper. We address Benefits, Blockers, Principles, Methods and Business Models for Open Architectures.
Guidelines for Architects intending to adopt Open Systems Architecture - June 2009
A list of fifteen steps that constitute a pragmatic method of developing Open Architectures or of opening legacy architectures.
The Case for Open Systems Architecture - December 2009
Based on a stochastic model of the development of a large modular system, we suggest that the cost of development of that system and the time to deliver it (schedule) can both be reduced, if the system is designed with an Open Architecture.
Why Large IT Projects Fail - August 2010
An argument that the fundamental reason Large projects fail to deliver to time or to cost is that requirements are allowed to drift.
Bibliography - September 2011
An annotated selection of books, papers and public websites that have influenced my thinking on Architecture and Open Systems.

This page is subject to frequent change. The date at the top reflects its most recent changes.