text: One final point: features of OWL and SWRL that new users frequently find frustrating are the Open 
  World Assumption (OWA) and lack of non-monotonic reasoning. The OWA was discussed in chapter 
  4.13. Non-monotonic reasoning will be discussed in section 11.1. For now, though remember that 
  SPARQL is*not*subject to*either*of these restrictions. With SPARQL one can do non-monotonic 
  reasoning and leverage the more common Closed World Assumption (CWA). E.g., one can test if the 
  value for a property on a specific instance exists or not and can take actions if that property does not exist. 