I need to get cXML message from Ariba in BizTalk do some processing and send as cXML to another endpoint.
Please suggest some pointers to how this can be done in BizTalk 2013.
I've done a lot of BizTalk+Ariba and there are no real blocking issues, but Ariba makes it much harder than it needs to be. This is not a problem with BizTalk, it's Ariba.
You can download the DTDs (yes, DTD still) from cxml.org then use the DTD Wizard in Visual Studio to generate the Xsd Schemas.
There will be some issues due to constructs supported in DTD but not Xsd. I just delete the offending structures. Never had to use them.
Depending on what you do, the lack of a namespace may or may not be a problem. I'd just get started and see what happens.
If you have any problems, come back and I can look at how I fixed it.