Gosh, I don't even know where to start with this one....
So, my mother calls me up a few weeks ago, before I left Comverse, and says, "Tom, I'm really confused about the differences between the P-CSCF and the S-SCSF... I know one is has something to do with replacing session border controllers, or is it a replacement for the HLR? No, that can't be right, can it? You really need to help me. I gotta get this done before my bridge game tonight."
"Well, Mom... I'm not quite too sure myself, as I don't even know what rev of IMS I'm designing to. Besides, why don't you leave all that IMS development to the Tier 1 NEPs. It's why they invented IMS in the first place, so that the smaller vendors could get locked out, while at the same time, locking in those large carriers to many more years of big, expensive iron. Besides, IMS is just an architecture, not a definitive specification, so why don't you call your bridge game an IMS compliant activity, and everyone will be happy. "
The title is so true, in so many ways.
p.s. I am pretty sure that if you took the entirety of the IMS specifications, in all the variances and splendor, and printed it out and put it in a big pile, the average human being standing upon it would not be able to survive the fall.