I agree with Ken. I think that we're a long way away from having truly soft analog IP. However, I think that hard analog IP does make sense today, and I think that there are opportunities for "firm" analog IP today as well to gain some of the advantages of re-use.
Chapter 8 of
- H. Chang, L. Cooke, M. Hunt, G. Martin, A. McNelly, L. Todd, Surviving the SoC Revolution, Kluwer Academic Publishers, 1999.
discusses some ideas on what firm and hard analog IP would be.
Also, you mentioned the VSI in general. Just to be certain, I think that the most applicable specification would be the "Analog/Mixed-Signal Extension Version 2 (AMS 1 2.x)". This describes in detail what an IP provider of hard analog IP would have to deliver to an IP integrator for the IP integrator to be successful. I believe that even if one went with "firm" IP, that ultimately the delivery of it to a mostly digital SoC would require that it be delivered as "hard" IP and thus this specification would still be applicable in part or in whole.
-Henry