Module 8: Miscellaneous Topics
Lecture 40: Skyline Queries
 

                                            

 

 

Bitmap algorithm
  • Assume that the domain of each dimension is discretized into values
  • Represent each value as a bitmap of size n bits
  • Assume that the dominating function is
  • Represent a value as a bitmap whose MSBs are set to 0 and LSBs set to 1
  • For an object, extract bit slices for appropriate dimensions
  • Bit slice for bit contains the corresponding bits of all objects
  • Bit slice corresponds to the -th MSB for dimension
  • Bitwise AND of of all dimensions produces
  • captures all objects that are better or equal in all dimensions
  • Bit slice corresponds to the -th MSB for dimension
  • Bitwise OR of of all dimensions produces
  • captures all objects that are strictly better in at least one dimension