Although many inconsistencies in literature about SOA exist most authors agree on the basic ‘publish - find – bind model’ shown in [1]. This model is useful to introduce the basic entities that interact within a SOA [MAS07]: 

 

As shown in [1], the whole process of finding the needed service is only possible using the service repository. In step (1) the service provider publishes a description of the service, the interface description and the contract to the service repository. In step (2) the service consumer retrieves this information from the service repository and chooses the preferred service. This decision is solely based on the information provided by the service repository and independent from any implementation details. Therefore, this model leads to a loose coupling between service provider and service consumer. The service provider could change the implementation of its service without affecting the service consumer as long as the interface does not change. The service could also be provided by another service provider without affecting the consumer and the consumer could also change without affecting the provider.