"alternative" and "progressive" rock

Here are two two terms from musical genres (or rather movements) that are both difficult to pinpoint. And while we are making endless debates what prog rock is (and is not), somehow we have an approximate idea.
Wikipedia offers a good article about what "alternative" rock is. But I want to know:

how are the terms progressive and alternative correlated to each other?

The term progressive widened after 80's, and especially after 90's and 00's. The term alternative was closely related to post-punk music in the beginning, but I guess it's not the case any more. Nowadays, I got an impression that every "rock" band that is not cheap pop, rnb or some other crap is alternative. Or at least "lite alternative". Are we living in the times when the term rock is equal to term alternative?

There are alternative bands that:
a) are not suitable for PA because they're not prog (Sonic Youth, Stereolab)
b) are included in PA as prog-related (Radiohead)
c) are included in PA under some sub-genre (Sigur Ros) or they are not included here, but (in my opinion) they should be.  (Pere Ubu)

One more thing, in the "suggest new bands" section it's a common case that someone suggests some band for addition, while somebody else replies "they're not prog, they just have some alternative overtones" etc etc.

So, are these two terms opposite to each other? Or one is sub-set of another?

I'm quite puzzled...

In the UK originally meant indie bands (often initially signed to indie labels), that offered some alternative music to the late 80's established pop chart bands - however, within 2-3  years many of the alternative bands were the establishment e.g. James, Madchester groups.

Edited by Dick Heath - February 17 2007 at 15:40

all UKers will remember the Manic Street Preachers who started as a glam rock band who said they'd release an album that would sell a billion copies and then split up forever. I have five of their albums and they got absorbed pretty quickly into the top 40 set while somehow managing to fool everyone that they were alternative and edgy.

Brilliant and biting lyrics, though, I suppose that helps.

edit: it's practically internet legend now that the top three genre tags on last.fm are "rock", "alternative" and "indie." although of course what's pop in the real world is scorned there to some extent. but music listeners on the whole are being tricked about what's alternative.


Edited by laplace - February 17 2007 at 19:20