One of the questions I'm often asked is whether my novel is autobiographical. I think the questioners mean, Did the events in your book really happen to you? Mostly the answer is no, though there is one incident in The Train to Orvieto that actually did happen to me and that provided the "seed" for the entire story. However, the story itself is still not autobiographical in the sense that a memoir is autobiographical.
The real question here is what the relationship between fiction and autobiography is. IMHO fiction almost can't be anything other than autobiography in the sense that it is a record of the imaginative journey a particular writer has taken and recorded. No matter what the writer's approach is, fiction is invariably a work of imagination. To read it as memoir, journalism or history is to mistake its intent.
The best discussion of this question is one I saw recently in Shop Talk, a collection of edited conversations with well known writers by Philip Roth. One writer, Aharon Appelfeld, a Holocaust survivor, sees the matter this way (p. 27): I have never written about things as they happened. All my works are indeed chapters from my most personal experience, but nevertheless they are not "the story of my life." The things that happened to me in my life have already happened, they are already formed, and time has kneaded them and given them shape. To write things as they happened means to enslave oneself to memory, which is only a minor element in the creative process. To my mind, to create means to order, sort out, and choose the words and the pace that fit the work. The materials are indeed materials from one's life, but ultimately the creation is an independent creature. I think Appelfeld gets it right.