well, obviously it's possible to dream *about* something before you experience it--take your dreams of childbearing. but i don't think that a dream can accurately portray a sensation or experience unless you have physically gone through that situation.

dreams are a product of our subconscious, and are often influenced by the day's events. for example: it's generally thought that a person has to see, read, or hear an advertisement 7-12 times before they take notice of it and think "i'm going to buy that." so say your subconscious mind saw part of an infomercial where a woman was using a food processor--as in, you were pretty much zoned out not realizing what you were staring at. that night, you dream about being in the kitchen (most likely yours) and using a food processor to chop lettuce. you take notice of the dream but don't think much of it. the next week, you've forgotten the dream but you realize you want/need a food processor, and buy one just in time to make that salad for the pot luck at work. so you're using the processor to chop lettuce and... "deja vu, i *soo* have done this before!"

so that's my take on the realistic attributes of a dream. i guess it sounds bit more like psychology than philosophy, but nonetheless.