Understanding Enterprise Business Services 3-7
PeopleSoft Financials. The substitution of the service provider has no impact on the requester or the client.
This kind of decoupling is accomplished by having the requesters and service providers converse using a mediator. In AIA, the EBS publishes services to requesters.
The requester binds to the EBS to access the service, with no direct interaction with the actual implementer of the service.
Hence, to achieve the loose coupling between service consumer and the provider, the EBS takes the role of mediator. Routing rules can be definitionally specified to direct
the EBS regarding how to delegate the request to the right service provider as well as to the right application instance. Situations might also occur in which the services that
invoke the EBS might have knowledge of whom the requests need to be delegated to. In this scenario, the services might supply the information in the EBM prior to
invoking the EBS.
For example, you may have two billing system implementations-one dedicated to customers who reside in Northern America and the second dedicated to the customers
residing in other parts of the world. The EBS evaluates this rule and deciphers the actual implementation that should be used for processing a specific message. Using
this approach, the clients and service requesters are totally unaware of the actual implementers. Similarly, the underlying service implementers are oblivious to the
client applications that made the request.
Note that while the architecture allows for an entire message containing all instances to be sent to one service provider as opposed to another, it does not allow for a subset
of the instances present in a message to go to one provider and the remaining instances to go to another provider.
3.5.3 Content-Based Selection of the Service Provider
This architecture enables cross-application business processes to use these EBS without regard to which application vendor is actually providing the implementation
or which of the multiple deployments that might exist is responsible for processing the request and providing the response.
To achieve the loose coupling, some aspects of the service interactions must be tightly coupled between the requester and the service provider. In a service-oriented
architecture SOA, there is no way to loosely couple a service entirely between systems. You must choose what aspects should be loosely coupled and what can be
tightly coupled.
Oracle AIA places importance on the client being unaware of who the service provider is, the language, the platform in which the services are implemented, and finally, the
communication protocol. So these aspects are totally decoupled. Making a change to one of these aspects has no impact on the client.
However, at design time, the requester explicitly specifies the name of the EBS operation, which in turn is responsible for identifying the actual service provider. The
data formats are also specified at design time and regardless of the actual service providers, the data formats needed to pass the content do not change. So changing
either the name of the EBS, the service operation, or the structure of the data formats will certainly impact the client. As mentioned in the previous sections, an EBM is
passed as a request; and another EBM is received as a response.
3.5.4 EBS Purpose
The purpose of the EBS is:
3-8 Concepts and Technologies Guide for Oracle Application Integration Architecture
■
To receive the request from the calling application.
■
To identify the implementation as well as the deployment that is responsible for providing the requested service.
■
To delegate the requested task to the right implementation.
■
To receive the response and return the EBM to the calling application. Figure 3–4
and Figure 3–5
show how EBS enables the loose coupling of requesters with the actual service providers.
Figure 3–4 EBS Enables Loose Coupling of Requesters with Service Providers
Figure 3–5 Example of GetAccount EBS
Understanding Enterprise Business Services 3-9
For more information about EBS see Designing and Developing Enterprise Business Services in the Oracle Fusion Middleware Developers Guide for Oracle Application
Integration Architecture Foundation Pack.
3.6 Enterprise Business Flow Processes
