This section describes what is SOAP RPC Presentation and how to represent RPC (Remote Procedure Call) with SOAP messages.
SOAP RPC Presentation is an extension of the SOAP framework specification that defines how RPC (Remote Procedure Call)
requests and responses should be presented by SOAP messages.
As programmers, we all understand that the following issues are involved to carry out a remote procedure call:
The target system which will perform the procedure and return the result.
The procedure name used to identify the procedure on the target system.
Input parameters that need to be passed to the procedure on the target system.
Return value which is returned directly by the procedure.
Output parameters that contain information affected indirectly by the procedure.
SOAP RPC Presentation defines the following rules to resolved the issues listed above:
1. The target system should be mapped as the target SOAP node, which should represented by a URI.
2. The nature of the procedure should be reviewed to see if it can be carried by other simpler SOAP extensions
like SOAP Web Method Feature. See other sections of this book for detail information on other SOAP extensions.
3. The procedure name should be reviewed. If the nature of the procedure is a request for information retrieval,
and the procedure name contains resource identifications that are needed to retrieve information, the target SOAP
node URI should be extended to include the resource identification parts of the procedure name.
4. Input parameters of the procedure should also be reviewed. If the nature of the procedure is a request for
information retrieval, and some input parameters represent resource identifications that are needed to retrieve
information, the target SOAP node URI should be extended to include those input parameters.
5. If the nature of the procedure is a request for information retrieval, and the procedure name and input
parameters can be entirely represented in the target SOAP node URI, this RPC invocation should be carried as
a Web method defined in the SOAP Web Method Feature specification.
6. If a RPC can not be carried out as a Web method, it should be invoked by as SOAP message with a SOAP body
element. The body element should use SOAP encoding and contains a single "struct" node representing the procedure name.
All input parameters should be represented as outbound edges originated from this node.
7. The target SOAP node should always return a SOAP message with a SOAP body element. The body element should
use SOAP encoding and contains a single "struct" node with any label. This node should have on outbound edge
labeled as "result" representing the RPC return value.
8. If there are any output parameters, they should be represented as outbound edges originated from the node described
in rule #7.
9. SOAP header blocks are optional in RPC invocation and response SOAP messages.
Note that SOAP RPC Presentation specification does not define how the communication should be carried out. Protocol
binding specification is totally independent of SOAP RPC Presentation specification.
