How to control transactions (WS-AT) between two web services in OSB?

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Could someone tell me if the OSB can have 2 diferents web services controlled by an unique transaction?

For instance: in the OSB there are two wsdl, each one with its own Business Service and ProxyService respectively. In my vb.net aplication I started a transaction, called the first web service succefully and from the second web service I got an exception. I expected the first web service undo its work because the vb.net aplication excute a rollback command. Is this possible? How can I do? Any sample or tip will be helpfull.

If I was developing without OSB, I would rely on WS-AT as shown in 6 Steps to Enable Transactions in WCF[^] for two web services dot net, or for one web service dot net and other java, http://www.ibm.com/developerworks/websphere/library/techarticles/0707_lo/0707_lo.html[^].

My question is basically: Is still possible to keep a single transaction between multiple web services when they are mediated by OSB? If so, is there a example showing how?