While I'm at it, let me record it here. This is again a "re-learn" that cost me many hours.
I need to access DVM in my XSLT inside my BPEL process. I have created my DVM file (myfile.dvm) inside the project, so "myfile.dvm" sits in the project folder. The correct way to access the file in xslt is:
<xsl:value-of select='dvm:lookupValue("myfile.dvm","column1-title", "value1","column2-title","default-for-column2")'/>
Here are the two things that cost me several hours to "re-learn":
1. JDEV UI has that tool you can test XSLT locally, it works great most of the time, but it DOES NOT work with DVM. So don't waste your time testing DVM in jdev locally. You have to deploy it to the server to run your test!
2. I thought my XSLT file sits in "xsl" subfolder, so I tried to access it as "../myfile.dvm" in my XSLT code. Well, that turned out to be wrong. After searching through my old code, I found out that you should access the file as "./myfile.dvm". That's it.