In a synchronous interaction, a client sends a request to a service (d1 in Figure 5-2), and receives an immediate reply (d2 in Figure 5-2). A BPEL process service component can be at either end of this interaction, and must be coded based on its role as either the client or the service. For example, a user requests a subscription to an online newspaper and immediately receives email confirmation that their request has been accepted. The following example shows the portType and operation part of the BPEL process WSDL file for this environment.

. . .
<wsdl:portType name="BPELProcess1">
      <wsdl:operation name="process">
         <wsdl:input  message="client:BPELProcess1RequestMessage" />
         <wsdl:output message="client:BPELProcess1ResponseMessage"/>
      </wsdl:operation>
</wsdl:portType>

Figure 5-2 provides an overview.