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Module: Mapping management

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Mapping management

Introduction

Mappings are declarative rules (expressed in R2RML) which defines the relationship between the underlying data (i.e. table, columns) and the entities in the ontology (i.e. concepts, properties). They are used to create virtualize RDF graphs from SQL databases.

The mapping analysis functionality provides a report to the end-user giving qualitiative indicators regarding some of the well-known mapping challenges.For example global inconsistency and global redundancy checks are implemented. This functionality is fully integrated in the Optique platform’s R2RML editor as shown below.

The mapping management page allows user to import/export mappings, create, rename, edit and delete mappings within the platform itself.

Exercice

1. Once Optique platform is installed (ref. installing Optique), data source setup and ontology create, navigate to the Mappings menu.

2. You may either create a new mapping using the Create button or import existing mapping(s) using the Import button.

3. For editing, simply click on the Mapping name hyperlink in the Collection column.

4. For Analysis, click on the analysis icon as shown below. Report is generated and added to the screen.

Mapping Management screen

Mapping Management screen

5. Optique has an integrated mapping editor, which enables the user to easily create and modify mapping rules. The editor has auto-complete features and analysis tools which guide the user through the process. See below:

Optique mapping editor

Optique mapping editor

 

6. The SQL query is defined in the “change or extend” link at the top.

7. The mapping itself starts with the Class mapping. Further all properties are added using the “Add Predicate/Object Mapping” link.

8. Preview of resulting triples is a useful tool to lokk into the generated RDF.

Note 1: Ontop module is effectively executing the mapping rules in the most efficient manner.

Note 2: you can bootstrap your data source to generate automatically an ontology and a set of mappings.

Resources

Resource: Video Demonstration of Mapping Editor.

This video gives a demonstration of the mapping editor of Optique.

Warning: The video is from 2014, so there is a significant difference between the version used in the video, and the newest version of Optique.

Northwind tutorial module 2 Task 2. Mapping

Task 2 will guide you through the process of mapping modification. You will learn how to link a simple data property from the ontology to the database.

Note: running the tutorial with editing rights requires installation of the Northwind tutorial using method 2 or 3. To read the tutorial method 1 (public demonstrator) is sufficient.

R2RML: RDB to RDF Mapping Language

This document describes R2RML, a language for expressing customized mappings from relational databases to RDF datasets. Such mappings provide the ability to view existing relational data in the RDF data model, expressed in a structure and target vocabulary of the mapping author’s choice. R2RML mappings are themselves RDF graphs and written down in Turtle syntax. R2RML enables different types of mapping implementations. Processors could, for example, offer a virtual SPARQL endpoint over the mapped relational data, or generate RDF dumps, or offer a Linked Data interface.

R2RML - The RDB2RDF Mapping Language

Illustration of R2RML mappings as RDF graph consisting of several rr:TriplesMaps, that specify how to map a logical table in the input relational database into RDF.

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