Half -blood

[Mandy]

  I thought a half blood was some one with one magical parent and 
one muggle parent, but some one recently posted that Dumbledor 
refered to Harry as a half-blood. Anyone have a good answer for this?

  One person I thought might be the half-blood prince was James. 
Nothing about his family has been said unless I missed it. Do we 
know if he was pure blood or half blood or muggle born? I suppose a 
lot is going to be dependant on how JKR defines half-blood and what 
exactly she means by prince.

  ande