Service Loose Coupling

Loose coupling can be thought of as the resilient relationship that exists among two or more systems or companies that have some sort of relationship based on exchange. Each transactional end should make its requirements explicit somehow and make very few, if any, assumptions about the other end. While the notion of loose coupling originated in computer systems, Karl Weick later brought it in to organizational studies.

Loose Coupling in Computing Loosely coupled computers systems are regarded as being useful in the event that either the destination or the source computing systems are subject to changes on a frequent basis.

Loose coupling can be thought of as a design goal that has to be sought out by companies who are in the process of implementing an Enterprise Messaging System.

There are numerous dimensions to the idea of loose coupling. Integration, for instance, between two applications may be coupled loosely in time through the usage of Message oriented middleware – meaning the availability of such a system does not have any affect on the other. On the other hand, integration might be coupled loosely in format through the utilization of middleware as a means of performing data transformation – i.e. differences in data models are not able to prevent integration. When it comes to Service Oriented Architecture or Web Services, loose coupling can mean simply that the implementation is concealed from the caller.

Loose coupling may be applied to friction free linking that is enabled by open architectures. Services that are loosely coupled, even if they might be employing incompatible system technologies, might be able to be joined together on demand as a means of creating composite services, or readily disassembled in to functional components. Through normative or inceptive means, participants are able to establish a shared semantic framework in order to ensure that messages retain a consistent meaning across the spectrum of participating services.

Loose coupling is thus descriptive as an approach in which integration interfaces are developed with very few assumptions among sending and receiving parties. This reduces the risk that any changes that take place in one particular application will make a change in a relating application necessary.

Loose coupling can also be thought of as a computer system wherein two or more physical processors share storage disks in a real time atmosphere. The system has to be designed in order to enable code to be shared. It must be reentrant and the records to be shared have to be protected via record locking.

The extent of the loose coupling can be measured through a notation of the quantity of changes within the data elements that might occur in the sending or receiving systems, and then determining whether the computers would still be able to communicate in a correct manner. Such changes might include items like

• New data elements that are added to messages
• Data elements that are omitted
• The order of data elements being altered
• The structure or name of a data element being altered

Loose coupling can be enhanced in a major way by transmitting messages through the use of a flexible file format like XML as a means of enabling subscribers to publish clear definitions of how they use this info subsequently. A subscriber, for instance, might wish to publish a collection of statements that was used to extract data from a publisher’s messages through sharing relevant Xpath expressions utilized for the transformation of data. Such a step would then allow a responsible publisher of data to see whether their subscriber’s extraction methods would work when a change is made to a published format.

By reducing the data passed in to a service to the key data, the loose coupling of services is then enhanced. A service, for instance, that transmits a letter is most reusable when only the customer identifier is passed and the customer address is obtained from within the service. This effectively decouples services because then they do not need to be called in a specific order.