Greg Ankesh 1

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  • Question is for the Presentation: Gregory Todd Williams SPARQL BGP Optimization Presentation
  • Question is asked by: Ankesh Khandelwal
  • The Question is:
  • In section 5.1 the selectivity estimation for bound object is done separately for bound and unbound properties.
    • This is contrary to the assumption that selectivities of s, p , o are independent.
    • When p is unbound the selectivity value can be >1, not just theoretically.
  • Selectivity Estimation is so naive, rudimentary. They should have at-least tried to estimate sel using sel(s)*sel(s/p)*sel(o/s,p) or sel(s)*sel(s/p)*sel(o/p) and suggested the required statistics and how these statistical informations be created. Moreover, this involves pre-processing (nothing done at query time). Only negative impact is the increase in size of summary data, but that's affordable.
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  • In section 5.1 the selectivity estimati …
  • In section 5.1 the selectivity estimation for bound object is done separately for bound and unbound properties.
    • This is contrary to the assumption that selectivities of s, p , o are independent.
    • When p is unbound the selectivity value can be >1, not just theoretically.
  • Selectivity Estimation is so naive, rudimentary. They should have at-least tried to estimate sel using sel(s)*sel(s/p)*sel(o/s,p) or sel(s)*sel(s/p)*sel(o/p) and suggested the required statistics and how these statistical informations be created. Moreover, this involves pre-processing (nothing done at query time). Only negative impact is the increase in size of summary data, but that's affordable.

e of summary data, but that's affordable.

Question asked byAnkesh Khandelwal  +
Question for the PresentationGregory Todd Williams SPARQL BGP Optimization Presentation  +
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