Databases Reference
In-Depth Information
RDFS and OWL Reasoning for Linked Data
Axel Polleres
1
, Aidan Hogan
2
, Renaud Delbru
2
,andJurgen Umbrich
2
,
3
1
Siemens AG Osterreich, Siemensstraße 90, 1210 Vienna, Austria
2
Digital Enterprise Research Institute, National University of Ireland, Galway
3
Fujitsu (Ireland) Limited, Swords, Co. Dublin, Ireland
Abstract.
Linked Data promises that a large portion of Web Data will
be usable as one big interlinked RDF database against which structured
queries can be answered. In this lecture we will show how reasoning -
using RDF Schema (RDFS) and the Web Ontology Language (OWL) -
can help to obtain more complete answers for such queries over Linked
Data. We first look at the extent to which RDFS and OWL features are
being adopted on the Web. We then introduce two high-level architec-
tures for query answering over Linked Data and outline how these can
be enriched by (lightweight) RDFS and OWL reasoning, enumerating
the main challenges faced and discussing reasoning methods that make
practical and theoretical trade-offs to address these challenges. In the
end, we also ask whether or not RDFS and OWL are enough and discuss
numeric reasoning methods that are beyond the scope of these standards
but that are often important when integrating Linked Data from several,
heterogeneous sources.
1 Introduction
Linked Data [36,2] denotes the emerging trend of publishing structured data on
the Web as interlinked RDF graphs [49] following a number of simple principles:
use HTTP URIs to name things, return RDF about those things when their
URIs are looked up, and include links to related RDF documents elsewhere on
the Web. These trends - and related trends with respect to embedding metadata
volume of RDF data being made openly available online, contributing to what
is often called the “Web of Data”.
The Semantic Web provides the necessary tools to query this data, (i) firstly
by defining RDF [49,35] as a universal data format; (ii) secondly by defining
SPARQL [60,30], a standard query language for RDF; and (iii) lastly by provid-
ing schema languages such as RDF Schema (RDFS) [13] and OWL [37], which
allow for adding rich semantics to the data.
It is the aim of this lecture to emphasise that all three components, and in
particular the reasoning capabilities enabled by RDFS and OWL, are essential to
enable usage of the Web of Data as “
one huge database
” as originally envisioned
by Tim Berners-Lee [9].
As opposed to standard reasoning and query answering in OWL, for instance
as described in the present volume in the chapter on Ontology-based Data Ac-
cess [47], reasoning over Linked Data poses several unique challenges:
