This document discusses the concept of coupling in system architecture. It notes that coupling affects complexity, adaptability, and behavior. Loose coupling reduces interdependencies but also interoperability, while tight coupling enables integration but with less flexibility. The document examines different types of coupling, including business, organizational, data, process, and implementation coupling. It argues that coupling is important to consider for system scale, economics of manufacturing versus agile systems, and the costs of semantic matching between systems.

1. Architecture and Coupling Richard Veryard September 2011

2. Motivation System architects need to pay attention to coupling. Because the degree and location of coupling in a system of systems critically affects its behaviour. Coupling also affects complexity and adaptability.

3. Not just IT systems … Consider the connection between the moulding shop and the paint shop in a factory. This is exactly the kind of architectural trade-off that enterprise architects should be qualified to consider.

4. Loose coupling is a judgement, not a mantra Loose Coupling Reduced interdependencies  reduced interoperability risk Minimize knowledge dependencies Tight Coupling Integration & interoperability  joined-up business 4

5. Inscription and Loose Coupling According to Simon, loose coupling gives you THREE different types of flexibility - technological flexibility, organizational flexibility AND flexibility in the relationship between technology and organization. Kai A. Simon, Business Processes and IT in the Pharmaceutical Industry(Dissertation) http://www.informatik.gu.se/%7Ekai Richard Veryard, Inscription and Loose Coupling (September 2005) http://rvsoapbox.blogspot.com/2005/09/inscription-and-loose-coupling.htm

6. Weick on Loose Coupling Karl Weick, Managing Change Among Loosely Coupled Elements

7. Coupling and complexity can be a consequence of scale At low volumes, a system may be able to operate effectively in asynchronous mode. At high volumes, the same system may have to switch to a more synchronous mode. If an airport gets two incoming flights per hour, then the utilization of the runway is extremely low and planes hardly ever need to wait. If the airport gets two incoming flights per minute, then the runway becomes a scarce resource demanding tight scheduling, and planes are regularly forced to wait for a take-off or landing slot. 7

8. Management Coupling Business Coupling Organization Coupling Data Coupling Process / Control Coupling Implementation Coupling Device Coupling In 2003 I identified many aspects of coupling and decoupling Richard Veryard, Component-Based Service Engineering (CBDI Journal, November 2003) Copyright © CBDI Forum

9. Business (Commercial) Coupling Richard Veryard, Component-Based Service Engineering (CBDI Journal, November 2003) Copyright © CBDI Forum

10. Organizational Coupling Richard Veryard, Component-Based Service Engineering (CBDI Journal, November 2003) Copyright © CBDI Forum

11. Information Coupling Richard Veryard, Component-Based Service Engineering (CBDI Journal, November 2003) Copyright © CBDI Forum

12. Process Coupling Richard Veryard, Component-Based Service Engineering (CBDI Journal, November 2003) Copyright © CBDI Forum

13. Implementation Coupling Richard Veryard, Component-Based Service Engineering (CBDI Journal, November 2003) Copyright © CBDI Forum

14. Device Coupling Richard Veryard, Component-Based Service Engineering (CBDI Journal, November 2003) Copyright © CBDI Forum

15. Management Coupling Richard Veryard, Component-Based Service Engineering (CBDI Journal, November 2003) Copyright © CBDI Forum

16. Coupling may affect design-time and/or run-time In simple manufacturing, the economics of scale involves long production runs, so that you can spread the setup costs across a large volume. In agile manufacturing, the economics of scope involves minimizing the setup costs, so that you can have shorter production runs without affecting the economics of scale. A major element of the setup costs for services involves matching the semantics. Therefore semantic and related forms of coupling are critically important for the economics of scope.

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