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|
Identifier |
000414365 |
Title |
Optimizations for the query language SPARQL - LD |
Alternative Title |
Βελτιστοποιήσεις για τη γλώσσα επερώτησης διασυνδεδεμένων δεδομένων SPARQL - LD |
Author
|
Γιαννάκης-Χαλβατζής, Αθανάσιος Ι.
|
Thesis advisor
|
Τζίτζικας, Γιάννης
|
Reviewer
|
Πλεξουσάκης, Δημήτρης
Φλουρής, Γεώργιος
|
Abstract |
Linked Data is a method for publishing structured data in the Web for assisting their linking and
integration. A constantly increasing number of organizations and owners publish their data
on the
Web as Linked Data and SPARQL is the standard query language. However the majority of SPARQL
implementations require the data to be available in advance in main memory or accessible
through a SPARQL endpoint.
SPARQL
-
LD is an extension of SPARQL 1.
1 (designed by FORTH
-
ICS) that
overcomes this restriction
and
allows fetching and querying RDF data from any Web source and format
i.e., RDFa, JSON
-
LD,
Microdata and Microformats
. Using SPARQL
-
LD, one can query a dataset corresponding to an RDF
dump, or a
dataset corresponding to the partial results of a query (i.e., discovered at query
execution time), or RDF data that are dynamically created by Web Services. This functionality can
motivate content owners to adopt the Linked Data principles and enrich the
ir digital content and
services with RDF, for having their data directly queryable via SPARQL
–
LD without having to create
and maintain an operational SPARQL endpoint.
In this thesis we focus on optimizations for SPARQL
-
LD, in particular on: (a) methods f
or exploring
the syntactic variations of graph patterns in a SPARQL query in order to choose a near to optimal
execution plan without the use of statistics (to this end we utilize query reordering techniques,
using selectivity estimation procedures on new
unbound variables for increasing efficiency and
decreasing intermediate results and thus the number of calls to remote sources), and (b) methods
for parallelizing RDF data retrieval by using SPARQL
-
LD for efficient data caching.
Finally, we report experi
mental results on real datasets for evaluating the efficiency as well as the
quality of the proposed optimizations. The results showed improved efficiency on SPARQL queries
in comparison to existing methods
|
Language |
English |
Subject |
Linked data |
|
RDF |
|
Semantic web |
|
Σημασιολογικός ιστός |
Issue date |
2018-03-23 |
Collection
|
School/Department--School of Sciences and Engineering--Department of Computer Science--Post-graduate theses
|
|
Type of Work--Post-graduate theses
|
Permanent Link |
https://elocus.lib.uoc.gr//dlib/5/3/8/metadata-dlib-1518158845-191256-7178.tkl
|
Views |
463 |