Title: message exchange

*message exchange* --- {excerpt}a communication between the ODE engine and a _[partner](partner.html)_ {excerpt}. Essentially, a message exchange is a web service invocation. Each message exchanges is associated with a WSDL _[port type]_ and _operation_. There are two types of message exchanges: _my role message exchanges_ and _partner role message exchanges_. The former represents invocations _on_ the server, while the latter represents invocations _by_ the server (this is BPEL terminology, so a look at the [spec](xxx) may be helpful).