morph-ldp: an r2rml-based linked data platform implementation

morph-LDP: An R2RML-based

Linked Data Platform implementation

Nandana Mihindukulasooriya1,2, Freddy Priyatna2,

Oscar Corcho2, Raúl García Castro1,2, and Miguel Esteban Gutiérrez1,2

1Center for Open Middleware 2Ontology Engineering Group, Facultad de Informática

Universidad Politécnica de Madrid, Spain

{nmihindu,fpriyatna,ocorcho,rgarcia,mesteban}@fi.upm.es

Objective: To expose relational databases as read / write Linked Data applications

Challenges: (i) Converting RDB to RDF and vice versa; (ii) Exposing RDF as read/write Linked Data

Approach: Combining the W3C Linked Data Platform (LDP) and W3C R2RML standards

Linked Data Platform

morph-LDP Use Case and Solution

An example – Retrieving the list of group members

R2RML Mapping Language

LDP4j morph-RDB

http://example.org/oeg/members/fpriyatna

identifies

Registration

Office

morph-LDP

Web App

Relational

Database

Library

Legacy Applications

configures

exposes

consumes Tabulator

OpenLink Data Explorer

ldspider LDIF

represents

Freddy

Priyatna

dereferences toLDP Request

Handler

LDP4j

Template Matcher

Morph Proxy

Morph Engine

Query Translator

R2RML Processor

Data Translator

A set of rules for

generating RDF

triples from database

rows/values.

A RESTful protocol

for HTTP-based

read/write

Linked Data.

Sta

ndard

s

Impl.

http://ldp4j.org https://github.com/fpriyatna/morph

• An open-source R2RML Engine implementation

• Data and query translator

• Beyond the R2RML specification

• support for read / write access

• An open-source Java LDP implementation

• Middleware layer for building LDP applications

• Beyond the LDP specification

• support for vocabulary management

LDP Resource (LDPR)

Non-RDF

Source

(LDP-NR)

RDF Source (LDP-NR)

LDP Container (LDPC)

Basic Container

Direct Container

Indirect Container

GET /oeg/members/ HTTP/1.1

Host: example.org

Accept: text/turtle

200 OK

HTTP/1.1 200 OK

Content-Type: text/turtle; charset=UTF-8

Link: <http://www.w3.org/ns/ldp#BasicContainer>; rel="type"

ETag: W/"195482449"

@prefix dcterms: <http://purl.org/dc/terms/>.

@prefix ldp: <http://www.w3.org/ns/ldp#>.

<> a ldp:BasicContainer;

dcterms:title "Members of OEG, UPM";

ldp:contains <http://example.org/oeg/members/asun> ;

ldp:contains <http://example.org/oeg/members/fpriyatna> ;

ldp:contains <http://example.org/oeg/members/mesteban>;

ldp:contains <http://example.org/oeg/members/nmihindu>;

ldp:contains <http://example.org/oeg/members/ocorcho> ;

ldp:contains <http://example.org/oeg/members/rgarcia> .

HTTP Request

HTTP Response

Mapping LDP and R2RML Concepts

R2RML Mapping

TriplesMap

LogicalTable

PredicateObjectMap

PredicateMap

ObjectMap

SubjectMap

RefObjectMap

SELECT ?s WHERE { ?s a foaf:Person .

FILTER (REGEX(STR(?s), "^http://example.org/oeg/members/")) }

SPARQL Query 3

1

10

SELECT id FROM oegmembers

5 SQL

LDP Request Handler

Query Translator

HTTP Request

ResultSet

Data Translator

-http://example.org/oeg/members/asun

-http://example.org/oeg/members/fpriyatna

-http://example.org/oeg/members/mesteban

-http://example.org/oeg/members/nmihindu

-http://example.org/oeg/members/ocorcho

-http://example.org/oeg/members/rgarcia

LDP Request Handler

-asun

-fpriyatna

-mesteban

-nmihindu

-ocorcho

-rgarcia

1

HTTP Response

23

45

7

8

9

10

M

D

6

SQL Query

oegmembers

id fname lname website email phone asun Asunción Gómez Pérez http://delici.. asun@fi.up +34913367417

fpriyatna Freddy Priyatna http://delici.. fpriyatna@f +34913363670

mesteban Miguel Esteban Gutierrez http://delici.. mesteban@ +34913363671

nmihindu Nandana Mihindukulasoori http://www. nmihindu +34913363670

ocorcho Oscar Corcho http://delici.. ocorcho@ +34913366605

rgarcia Raul Garcia Castro http://delici.. rgarcia@fi +34913366596

D

@prefix rr: <http://www.w3.org/ns/r2rml#> .

@prefix foaf: <http://xmlns.com/foaf/0.1/> .

<TriplesMapPerson>

a rr:TriplesMap;

rr:logicalTable [ rr:tableName "oegmembers" ];

rr:subjectMap [ a rr:Subject; rr:class foaf:Person;

rr:template “http://example.org/oeg/members/{id}";

rr:termType rr:IRI; ];

rr:predicateObjectMap [

rr:predicateMap [ rr:constant foaf:firstName ];

rr:objectMap [ rr:column “fname"; rr:termType rr:Literal; ]; ];

rr:predicateObjectMap [

rr:predicateMap [ rr:constant foaf:lastName ];

rr:objectMap [ rr:column “lname"; rr:termType rr:Literal; ]; ];

…

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