I’m studying WSDL 1.1 documentation and came across this confusing statement:
“Note that a request-response operation is an abstract notion; a particular binding must be consulted to determine how the messages are actually sent: within a single communication (such as a HTTP request/response), or as two independent communications (such as two HTTP requests)”
What does this mean exactly? I understand that WSDL defines web service interfaces, but I’m struggling to grasp how request-response patterns can work as either single or dual communications.
Could someone explain this concept with a practical example? Maybe show how the same operation might be implemented differently depending on the binding used?
think of it like ordering food. u can call 1 time and get ur order confirmed right away (like a single HTTP request/response), or you could text it and then wait for a reply (that’s dual). same order, just different ways the service can handle it.
The difference lies in the abstraction of the operation and its implementation. WSDL 1.1 defines operations in a generic manner, specifying the messages exchanged without detailing the transport method. The binding section clarifies how the communication occurs.
For instance, consider a getAccountBalance operation categorized as request-response. When using HTTP binding, a single POST request can fetch the information in one go. Conversely, with JMS binding, the request might go to one queue, and the response is retrieved from another, resulting in two distinct communications. Ultimately, while the operation remains the same—sending account details and receiving balance information—the method of transport varies depending on the binding protocol selected.
WSDL’s big advantage is separating what happens from how it happens. When you define a request-response operation in the abstract section, you’re just saying “this service takes message A and returns message B” - no mechanics involved. I ran into this while working with SOAP services that had to support both sync and async clients. The same operation definition worked whether clients waited for immediate HTTP responses or got responses hours later through callbacks after their requests were queued. The binding decides if your client opens one connection and waits, or sends a message and subscribes for the response separately. Same service contract, different performance and reliability needs - no need to change the core operation.