Could the holodeck create a fictional character just from analyzing stories that have been written about them?
Or would it need a living example?
Well, any simulation of a living person is going to have to be modeled on data about living people. If a prose story describes a character as "a short, slender, dark-haired woman," the computer's going to have to extrapolate a ton of other details somehow, so it'd probably have to draw on examples of real people who fit those descriptions and do some kind of statistical estimate or randomization or whatever to select other attributes. Or, a living person could create a holoprogram based on that story and cast actors in the roles to use as templates as I've been saying. Both hypothetically could be done, but a holocharacter modeled on a living actor's performance would probably feel more lifelike and convincing than one simulated purely by computer algorithms, just as sampled instruments sound more real than synthesized ones.