Algebraic Optimization of RDF Graph Pattern Queries on MapReduce - Large Scale and Big Data: Processing and Management - page 185

Query Q1: Retrieve vendor and review details
of product offers delivered within three days

J 2
Obj=Obj

Subject Property Object

& V 1 homepage www.ven..

SJ 3
Sub=Sub

& V 1 label Vend1

& V 1 country US

…
σ(P='rating1') T

SJ 1

J 1
Sub=Obj

& Off 1 vendor & V 1

σ(P='revFor') T

J 1
(obj-sub)

& Off 1 price 1008

SJ 2
Sub=Sub

& Off product & Pr 1

1

SJ 2

&R1 reviewer & Rev 1

…

J 2
(obj-obj)

&R1 revFor & Pr 1

SJ 1
Sub=Sub

σ(P='vendor') T σ(P='product') T

SJ 3

& Pr 1 prodFeature & Pf 1

σ(P='label') T & Pr 1 prodFeature & Pf 2

… … …

σ(P='homepage') T σ(P='country') T

(a) (b) (c)

FIGURE 6.1 (a) Example RDF triple relation T, (b) example SPARQL query Q1, and (c) corresponding relational algebra plan.