It is opposite and it isn't. The back of a knit is a purl, the back of a purl is a knit - that's the opposite part. You don't try to knit the opposite of how you did a stitch on the previous row, trying to figure that out does overcomplicate it. You knit a stitch the way it looks on the row you're doing, forget what you did to it before.
So for ribbing, if it looks like a V knit st, knit it, if it looks like a purl bump, purl it. For seed stitch though, if it looks like a V, purl it and if it looks like a bump, knit it. Cast on about 15 sts and try it out.
sue- knitting heretic