What are the differences between the Instance-Id, the ECID and the Dialog-ID? (In the Enterprise Manager 11g WebGui you can search for instances with these criteria.)
A unique Instance ID is created whenever a new instance of a SOA composite application is initiated either automatically by an external consumer of the application, or manually by an administrator from the Test Web Service page.
Execution context ID (ECID) value enables you to track a message flow that crosses instances of different composite applications.
Conversation ID is nothing but the correlation id between two BPEL processes. I've also seen some cases when conversation id was populated with AQ MSG ID when AQ Adapter or Application Adapter was used.
There is no such field as "Dialog-ID" in the standard search section of Oracle EM 11g unless you have added composite Sensors to the SOA composite.