I only see a VPI usage/ routine definitions section within the Verilog AMS reference manual as part of the Cadence doc folder. I am wondering where can I get the most recent version of the "VPI User Guide and Reference"? I found the 1999, version 2.0 pdf online, but can't find any recent versions. The VPI section within the Verilog AMS reference manual is drastically different from the 1999 "VPI User Guide and Reference" which has more detailed, guiding a new user into VPI approach, so I was hoping to get an up to date version, is there one more up to date than 1999?
I'm not sure exactly what you need, and I admit I've not found any nice up to date "user guide" to the VPI in all my travels, however the API reference is given in the IEEE1800-2012 LRM, which is available for free via the Accellera website. This document has object model diagrams and explanations of the properties and methods. I use it when writing VPI applications and whilst it's not always totally clear, it's generally pretty good.
Also, if you're looking for documentation in general, you should consider logging into support.cadence.com, and using the search facility there. We've made huge usability improvements over the last year and it's a great place to find lots of examples, app notes, rapid adoption kits as well as the basic documentation.