Is it possible to publish stories that are considerable developments of much shorter stories that have already been published? E.g. if you take a 100 word story and develop it into a 1000 word flash fiction, or short story, or even novel. At one point is it so different that it is not considered previously published?
Are you copying the characters & the technology, etc.? Though the Space Odyssey was based off of the Sentinel it wasn't a 100% transfer. Wilson is the main character / persona in Sentinel - Bowman in Space Odyssey. It was a basis, a stepping stone. Sort of like how Mocha Dick by Reynolds became Moby Dick by Melville. However, in this day and age where people are quite pro-copyright, copyright infringement, etc., it'd be better to be cautious than anything. As long as the flash fiction isn't obviously a carbon copy of the short fiction entitled Butternut Squash [a pseudo title obviously] there shouldn't be too big a problem.
I was talking about an author extending his or her own work. E.g. if I publish a 100 word story, then can I still extend that to a longer story (e.g. 1000 words or more) and then submit to a magazine that doesn't publish reprints? This may be more to do with policies than copyright law.