Robert Sawyer again has a lovely entry in his blog. It's his definition of science fiction. It's short, but it sums up the genre pretty well. I should note that he doesn't write like I do; I doubt that he would write a novel with a medieval historical backdrop that basically contains "Harry Potter-like" elements. But science fiction contains a pretty wide variety of "critters", so to speak, so I think that the "alternate reality" he speaks of would certainly fit anything I'm writing. Or what my writing-partner friend is writing. Or any number of writers are writing. Be that as it may, for anyone interested in science fiction, or writing in general, the Robert Sawyer blog and website is a good place to go from time to time.