Algebraic Optimization of RDF Graph Pattern Queries on MapReduce - Large Scale and Big Data: Processing and Management - page 196

RDF triple relation Groups of triple or “TripleGroups” Graph pattern query

Subject
& V 1
& V 1
& V 1
& V 1
& Off 1
& Off 1
& Off 1
& Off 1
& Off 2
& Off 2

Property
homepage
label
country
homepage
vendor
price
product
label
price
vendor

Object
www.vend...
Vendor1
US
www.vend...
& V 1
1008
& Pr 1
Offer1
360
& V 1

SELECT ?vlabel, ?hpage, ?price,....
WHERE { ( homepage , www.vendors.org.UK/V1)

( label , Vendor1),
( country , US),
( homepage , www.vendors.org.US/V1)

?v homepage ?hpage .
?v label ?vlabel.
?v country ?vcountry .

tg 1 =

& V 1,

SJ1

Group
By
Subject

?o vendor ?v .
?o price ?price .
?o label ?olabel .
?o product ?prod .

( vendor , & V 1)
( price , 1008),
( product , & Pr 1),
( label , Offer1)

tg 2 =

& Off 1, SJ2

(Missing
edges)

( price , 360)
( vendor , & V 1)

tg 3 = & Off 2,

FIGURE 6.5 Group By on the Subject column of a triple relation yields groups of triples that are potential matches to the star subpatterns in the query.