In BPEL, it is quite easy that if we don't specify the version during partnerlink invocation, it will use the default one. But in ESB, especially when ESB is calling BPEL via native binding the version of the BPEL process is hard coded inside the routing rule. This was quite annoying because this pattern is heavily used in AIA and redeploying newer version of BPEL requires change in routing rule in ESB.
In 10.1.3.5, Oracle released a new feature which solves this problem. After 10.1.3.5 upgrade, if you deploy any BPEL process, it creates a separate version in BPELSystem called "default" which is visible in ESB Console as well as JDeveloper.
If we select default during routing rule, then the default version of the BPEL process would be called from ESB during native invocation. Therefore if we change the BPEL default version or redeploy BPEL process with higher version, it won't require change in ESB routing rules.