Business processes consist of individual process steps that can vary in how extensive they are. One or more functions are then assigned to these steps; an executing software component is then assigned to each function. Clearly, the heterogeneous nature of system landscapes in enterprises makes it impossible to implement all the necessary functions associated with a complete process using the same technology on the same component. A modern software infrastructure must be in the position to integrate functions, implemented on widely differing software components, in one effective complete process. Until now, the combination of different applications has largely been based on manually declared interfaces, message formats, and agreements between business partners.
Web services simplify this process. They are based on open, generally accepted standards. They enable you to combine functions in a single process, even if they are implemented in widely differing software components. Web services are standalone, executable entities that can be published, searched for, and called, across a network.
The SAP Web Application Server implements the following basic Web services standards: eXtensible Markup Language (XML); Simple Object Access Protocol (SOAP); Web Service Definition Language (WSDL); and Universal Description, Discovery, and Integration (UDDI).
In the documentation that follows, we assume that the reader is familiar with Web service standards and techniques. You will find a general introduction to the Web Services topic under Sun Microsystems, in the pages of W3C, and in the general explanations for standardization organization OASIS under the topic UDDI.
Enterprises can extend their solutions by using Java or ABAP Web services, or both. If your priority in programming an application is the selection of data, the integration of an ABAP Web Service could be appropriate. Conversely, if you are implementing processes that involve different business partners and systems, it may be beneficial to program in Java and integrate Java Web Services.
The Web Service Framework consists of:
· The development environment for the ABAP Engine
· The development environment for the J2EE Engine
· Tools that support UDDI registration
· A distributed, interoperable SOAP runtime (ABAP and J2EE Engine)
Processing of SOAP requests using the Internet Communication Framework
The SAP Exchange Infrastructure is a key area in SAP NetWeaver. The Exchange Infrastructure provides an open, process-oriented integration infrastructure for the unhindered flow of information and for XML-based message exchanges. Systems integrated using SAP XI exchange messages over the Integration Server.
The programming model for XI ABAP proxies and Web services has been unified. The advantage of this is that both technologies can be implemented so that they complement one another. Messages can be sent and received either using the XI runtime or the Web service runtime.
Additional proxy runtime services can be controlled using protocols that you request using a proxy method. The features you have available depend on whether you are using the Web Service Framework or the Exchange Infrastructure for communication.
The ABAP Workbench offers an environment where you can publish, search for, and call Web services. It enables the SAP Web Application Server to act both as a server and client for Web services.
The Web service infrastructure enables developers to:
· Publish independent function that were implemented as RFC-enabled function modules, function groups, BAPIs, or XI message interfaces. This includes functions available as part of mySAP.com solutions, or functions developed by customers or partners. The Web service can be used across the entire Internet using standard protocols and can easily be added to any development environment. (See also Creating a Web Service).
· Consume Web services, regardless of where they are stored or how they are implemented. Business processes can be implemented across several systems, either within an enterprise or across several enterprises. (See also Consuming Web Services.)
The following triangle shows the basic architecture of the Web Service Framework:
After the functions have been implemented, a Web service interface must be created that provides a representation of the Web service for the user. This interface offers an abstraction layer and thus independence from the specific implementation used. Based on this interface, the Web service is configured and can be called at runtime. Publishing Web services in a UDDI Registry is supported by the UDDI client functions in the SAP Web AS.
You can store Web service definitions and released Web Services in a UDDI Registry. WSDL documents provide the basis of the Web service client, which can then be searched for in the UDDI using either a browser or the standard UDDI APIs. Web services can be published and searched for in all registries that conform to the standard. SAP also offers a public UDDI Business Registry under uddi.sap.com.
The SAP Web AS allows you to integrate Web services. It can generate Web service clients from WSDL files.
Web services and Web service standards develop quickly; new standards are being presented continually at standardization committees. However, these extended standards – such as security standards or additional protocols – can easily be integrated in the Web Service Framework using SAP.