All concepts surrounding Enterprise Services or services in general can be broken down into two distinct categories. Either they fall into the process of provisioning or consumption. Both processes differ significantly but are closely interlinked. In order to help beginners in the area of service-oriented architecture a short and a long introduction to these categories:
In Short:
Provisioning: Building a novel service
- Modeling: create a visual representation
- Define: create the service description (input/ output)
- Implementation: create the coding
- Publishing: make it known to the world
Consumption: Using an existing Service
- Discovery: Find an existing service
- Testing: Try out the service
- Consumption: Use the service(s) in dedicated user interfaces or integration scenarios
- Process Composition: Bring multiple user interfaces, events, roles, systems etc. together to fulfill a dedicated process
In Long:
Providing Services
Provisioning outlines the process of building and delivering services. After the service candidates have been identified (=scenario/ landscape assessment), the provisioning of these may begin within a four step approach:
- Modeling is the crucial first step in outlining the service's functionality in a broader scope. It constitutes the creation of a visual ‘picture' of all the functionality (provided via individual services) in one organization. To this end, the Enterprise Services Builder (ES Builder) offers a modeling environment where one can create various models as part of the Enterprise Services Repository (ESR). This model-driven service development provides a broad set of advantages which are elaborated in the ESR Documentation, along with explanations on SAPs modeling entities.
- Definition follows modeling and takes also place in the ES Builder. The intention of the definition phase is the creation of the WSDL file - the service interface description. Starting from the model, assignments are created out of which the definition objects are created. Definition and model are therewith linked. The ultimate result of the service definition is a design-time WSDL. A pure description of the service without specific information about where and how the functionality is provided; generally speaking the input and output message with data types.
- Implementation describes the process of ‘turning' the design-time WSDL file into a run-time WSDL. This means implementing the coding (basically any modern programming language can be used) and finally adding the system and transportation specific information to the WSDL, to facilitate communication with the service later. The original service description (design-time WSDL) is hence enriched with additional endpoint information and becomes a run-time WSDL. The example Enterprise Service "Find Customer Address Basic Data by name and Address" shows therefore one design time WSDL (labeled ESR) and one run time WSDL (labeled back-end).
- Publication is all about making the service known to the world - publishing the WSDL(s), specifically the run time WSDL to a dedicated place - the Services Registry. The service can then be found via search criteria or classifications. Publication to a Services Registry is optional and not explicitly mandatory for consumption - it acts only as facilitator for retrieving/ finding existing services along with their endpoint information. SAPs Services Registry is part of the ESR and based on the open UDDI v3 standard.
Consuming Services
Consumption outlines the process of using or invoking already provided services during runtime. This overall process can be structured into four major steps
- Discovery describes the process of identifying and physically finding existing services along with their endpoint information via typically search criteria or classification schemas. This activity is typically performed within the Services Registry.
- Testing describes the use of test data to invoke the service via its endpoints and clarify if the service is working according to the given premises and expectations. Services within the Enterprise Services Workplace can be tested by locating them in the Services Registry and from there starting the WS Navigator
- Consumption constitutes the main activity and describes the invocation of services using their endpoints to create user interfaces for end users or integration scenarios for more automated communication. Within SAP either Composition Environment or the Process Integration can be mentioned here as respective tools.
- Process Composition is all about realizing entire processes in which multiple consumed services along with their user interfaces, associated roles, events and so forth are brought together to flexibly fulfill a dedicated business requirement.
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