Data Warehouses and the Semantic Web - Data Warehouse Systems: Design and Implementation - page 535

logical table ,a subject map , and zero or more predicate object maps . A logical
table is either a base table or a view (using the predicate rr:tableName )or
an SQL query (using the predicate rr:sqlQuery ). A predicate object map is
composed of a predicate map and an object map. Subject maps, predicate
maps, and object maps are either constants ( rr:constant ), column-based
maps ( rr:column ), or template-based maps ( rr:template ). Templates use brace-
enclosed column names as placeholders. As an example, Fig. 14.3 shows how
a portion of the dimension table Product is mapped to RDF using R2RML.
This mapping can be then applied to any instance of the table to produce
the triples. We next show the mapping document, which, together with the
instance of the table, will produce the RDF graph:

#TriplesMap_Product

rr:logicalTable rr:subjectMap rr:predicateObjectMap

rr:predicate
rr:objectMap

rr:predicate
rr:objectMap

rr:tableName rr:template rr:class

Product ../{ProductKey} ex:product ex:productName ex:unitPrice

rr:column rr:column

ProductName UnitPrice

Fig. 14.3 R2RML mapping of the Product dimension

@prefix rr: < http://www.w3.org/ns/r2rml# > .
@prefix rdf: < http://www.w3.org/1999/02/22-rdf-syntax-ns# > .
@prefix rdfs: < http://www.w3.org/2000/01/rdf-schema# > .
@prefix ex: < http://example.org/ > .

< #TriplesMap Product >
a rr:TriplesMap ;
rr:logicalTable [ rr:tableName '' Product '' ];
rr:subjectMap [
rr:template '' http://example.org/product/ { ProductKey } '' ;

rr:class ex:product ] ;
rr:predicateObjectMap [
rr:predicate ex:productName ;
rr:objectMap [ rr:column '' ProductName '' ; rr:language '' en '' ];];
rr:predicateObjectMap [
rr:predicate ex:unitPrice ;
rr:objectMap [ rr:column '' UnitPrice '' ; rr:datatype rdfs:integer ] ; ] .

The triples map above (corresponding to the table Product ) is called
< #TriplesMap Product > . The logical table is the table Product ,andthe