how good is your sparql endpoint? a qos-aware sparql endpoint monitoring and data source selection...
DESCRIPTION
Due to the decentralised and autonomous architecture of the Web of Data, data replication and local deployment of SPARQL endpoints is inevitable. Nowadays, it is common to have multiple copies of the same dataset accessible by various SPARQL endpoints, thus leading to the problem of selecting optimal data source for a user query based on data properties and requirements of the user or the application. Quality of Service (QoS) parameters can play a pivotal role for the selection of optimal data sources according to the user's requirements. QoS parameters have been widely studied in the context of web service selection. However, to the best of our knowledge, the potential of associating QoS parameters to SPARQL endpoints for optimal data source selection has not been investigated. In this paper, we dene various QoS parameters associated with the SPARQL endpoints and represent a semantic model for QoS parameters and their evaluation. We present a monitoring service for the SPARQL endpoint which automatically evaluates the QoS metrics of any given SPARQL endpoint. We demonstrate the utility of our monitoring service by implementing an extension of the SPARQL query language, which caters for user requirements based on QoS parameters and selects the optimal data source for a particular user query over federated sources.TRANSCRIPT
How good is your SPARQL endpoint?
A QoS-aware SPARQL endpoint monitoring and data source
selection mechanism for federated SPARQL queries
Ali Intizar and Alessandra Mileo
How good is your SPARQL endpoint?
A QoS-aware SPARQL endpoint monitoring and data source
selection mechanism for federated SPARQL queries
Ali Intizar and Alessandra Mileo
How good is your SPARQL endpoint?
A QoS-aware SPARQL endpoint monitoring and data source
selection mechanism for federated SPARQL queries
Ali Intizar and Alessandra Mileo
How good is your SPARQL endpoint?
A QoS-aware SPARQL endpoint monitoring and data source
selection mechanism for federated SPARQL queries
Ali Intizar and Alessandra Mileo
28/10/2014 2
Linked Open Data and SPARQL Endpoints
• Linked Data • LOD cloud
28/10/2014 2
Linked Open Data and SPARQL Endpoints
• Linked Data • LOD cloud
28/10/2014 2
Linked Open Data and SPARQL Endpoints
• Linked Data • LOD cloud
• SPARQL Endpoints
28/10/2014 2
Linked Open Data and SPARQL Endpoints
• Linked Data • LOD cloud • SPARQL Endpoints • Both pubic and private
28/10/2014 2
Linked Open Data and SPARQL Endpoints
• Linked Data • LOD cloud • SPARQL Endpoints • Both pubic and private • Allow easy access to linked data using SPARQL queries • Provide a querying interface
28/10/2014 2
Linked Open Data and SPARQL Endpoints
• Linked Data • LOD cloud • SPARQL Endpoints • Both pubic and private • Allow easy access to linked data using SPARQL queries • Provide a querying interface
• Open Data Management Tools
28/10/2014 2
Linked Open Data and SPARQL Endpoints
• Linked Data • LOD cloud • SPARQL Endpoints • Both pubic and private • Allow easy access to linked data using SPARQL queries • Provide a querying interface
• Open Data Management Tools • Datahub
28/10/2014
Linked Open Data and SPARQL Endpoints
• Linked Data • LOD cloud • SPARQL Endpoints • Both pubic and private • Allow easy access to linked data using SPARQL queries • Provide a querying interface
• Open Data Management Tools • Datahub • LOD Stats
2
28/10/2014
Linked Open Data and SPARQL Endpoints
• Linked Data • LOD cloud • SPARQL Endpoints • Both pubic and private • Allow easy access to linked data using SPARQL queries • Provide a querying interface
• Open Data Management Tools • Datahub • LOD Stats
• SPARQL Endpoint Description • Vocabulary for Interlinking Datasets • Service Description
2
28/10/2014 3
Ranking of the SPARQL Endpoints
• Multiple SPARQL endpoints can represent the same dataset
28/10/2014 3
Ranking of the SPARQL Endpoints
• Multiple SPARQL endpoints can represent the same dataset • Which one is the best for me?
28/10/2014 3
Ranking of the SPARQL Endpoints
• Multiple SPARQL endpoints can represent the same dataset • Ranking of the SPARQL endpoints
28/10/2014 4
Ranking of the SPARQL Endpoints
• Multiple SPARQL endpoints can represent the same dataset • Ranking of the SPARQL endpoints • Based on QoI/QoS Parameters
28/10/2014 4
Ranking of the SPARQL Endpoints
• Multiple SPARQL endpoints can represent the same dataset • Ranking of the SPARQL endpoints • Based on QoI/QoS Parameters
28/10/2014 5
QoS Parameters for SPARQL Endpoints
For QoS based ranking of the SPARQL endpoints • Identification of the various QoS parameters associated with
the SPARQL endpoints
• Semantic respresentation of the identified QoS parameters
• Extension of the existing SPARQL endpoints description vocabularies (VoID/SD) to associate QoS parameters
• Evaluation techniques for the QoS metrics
• Continuous monitoring of the SPARQL endpoints to generate QoS profiles
28/10/2014 5
QoS Parameters for SPARQL Endpoints
For QoS based ranking of the SPARQL endpoints • Identification of the various QoS parameters associated with
the SPARQL endpoints
• Semantic respresentation of the identified QoS parameters
• Extension of the existing SPARQL endpoints description vocabularies (VoID/SD) to associate QoS parameters
• Evaluation techniques for the QoS metrics
• Continuous monitoring of the SPARQL endpoints to generate QoS profiles
28/10/2014
QoS Parameters for SPARQL Endpoints
• Performance
• Response Time • Execution Time • Throughput • Error Rate
6
28/10/2014 6
QoS Parameters for SPARQL Endpoints
• Performance
• Response Time • Execution Time • Throughput • Error Rate
• Data Quality
• Accuracy • Data Consistency • Completeness • Freshness
28/10/2014 7
QoS Parameters for SPARQL Endpoints
• Interoperabiilty
• SPARQL Version • Additional Features • Restricted Features
28/10/2014 7
QoS Parameters for SPARQL Endpoints
• Interoperabiilty
• SPARQL Version • Additional Features • Restricted Features
• Availability
• UpTime • DownTime • MeanUpTime • MTTR
28/10/2014 8
QoS Parameters for SPARQL Endpoints
• Licensing • PDDL • ODC-By • ODC-ODbL • CC0 0.1 Universal
28/10/2014 8
QoS Parameters for SPARQL Endpoints
• Licensing • PDDL • ODC-By • ODC-ODbL • CC0 0.1 Universal
• ResultSet • Size Limit • Result Format
28/10/2014 8
QoS Parameters for SPARQL Endpoints
• Licensing • PDDL • ODC-By • ODC-ODbL • CC0 0.1 Universal
• ResultSet • Size Limit • Result Format
• Dataset Description • VoID • SD
28/10/2014 9
QoS Parameters for SPARQL Endpoints
For QoS based ranking of the SPARQL endpoints • Identification of the various QoS parameters associated with
the SPARQL endpoints
• Semantic respresentation of the identified QoS parameters
• Extension of the existing SPARQL endpoints description vocabularies (VoID/SD) to associate QoS parameters
• Evaluation techniques for the QoS metrics
• Continuous monitoring of the SPARQL endpoints to generate QoS profiles
28/10/2014 10
QoS Parameters for SPARQL Endpoints
• Semantic Description of SPARQL Endpoint (VoID/SD) • QoS Profile of SPARQL Endpoints
QoSProfile
Property SubClass
QoSProfileEndpoint QoSProfileDefault
QoSProfileUser
SPARQL Endpoint
has
28/10/2014 10
QoS Parameters for SPARQL Endpoints
• Semantic Description of SPARQL Endpoint • QoS Profile of SPARQL Endpoints
QoSProfile
Property SubClass
QoSProfileEndpoint QoSProfileDefault
QoSProfileUser
SPARQL Endpoint
has
28/10/2014 10
QoS Parameters for SPARQL Endpoints
• Semantic Description of SPARQL Endpoint • QoS Profile of SPARQL Endpoints
QoSProfile
Property SubClass
QoSProfileEndpoint QoSProfileDefault
QoSProfileUser
SPARQL Endpoint
has
28/10/2014 10
QoS Parameters for SPARQL Endpoints
• Semantic Description of SPARQL Endpoint • QoS Profile of SPARQL Endpoints • QoS Profile 1. Endpoint 2. Default 3. User
QoSProfile
Property SubClass
QoSProfileEndpoint QoSProfileDefault
QoSProfileUser
SPARQL Endpoint
has
28/10/2014 11
QoS Parameters for SPARQL Endpoints
hasValue
QoSProfile
QoSParameter
Name
QoSCategory
Value QoSMetric
QoSWeight
Tendency
NonNumericMetricNumericMetricExactNumeric
IntervalNumeric
BooleanMetric
LinguisticMetric GradingMetric
No
HighMidLow
QoSUnit
Numeric Value
TextValue
Yes
hasvalue
hasvalue
hasvalue
hasvalue
hasvalue
endstart
hasName hasTendency
hasCategory
contains
hasWeight
hasMetric
isMeasuredIn
sameAs
28/10/2014 11
QoS Parameters for SPARQL Endpoints
hasValue
QoSProfile
QoSParameter
Name
QoSCategory
Value QoSMetric
QoSWeight
Tendency
NonNumericMetricNumericMetricExactNumeric
IntervalNumeric
BooleanMetric
LinguisticMetric GradingMetric
No
HighMidLow
QoSUnit
Numeric Value
TextValue
Yes
hasvalue
hasvalue
hasvalue
hasvalue
hasvalue
endstart
hasName hasTendency
hasCategory
contains
hasWeight
hasMetric
isMeasuredIn
sameAs
28/10/2014 11
QoS Parameters for SPARQL Endpoints
hasValue
QoSProfile
QoSParameter
Name
QoSCategory
Value QoSMetric
QoSWeight
Tendency
NonNumericMetricNumericMetricExactNumeric
IntervalNumeric
BooleanMetric
LinguisticMetric GradingMetric
No
HighMidLow
QoSUnit
Numeric Value
TextValue
Yes
hasvalue
hasvalue
hasvalue
hasvalue
hasvalue
endstart
hasName hasTendency
hasCategory
contains
hasWeight
hasMetric
isMeasuredIn
sameAs
28/10/2014 11
QoS Parameters for SPARQL Endpoints
hasValue
QoSProfile
QoSParameter
Name
QoSCategory
Value QoSMetric
QoSWeight
Tendency
NonNumericMetricNumericMetricExactNumeric
IntervalNumeric
BooleanMetric
LinguisticMetric GradingMetric
No
HighMidLow
QoSUnit
Numeric Value
TextValue
Yes
hasvalue
hasvalue
hasvalue
hasvalue
hasvalue
endstart
hasName hasTendency
hasCategory
contains
hasWeight
hasMetric
isMeasuredIn
sameAs
28/10/2014 11
QoS Parameters for SPARQL Endpoints
hasValue
QoSProfile
QoSParameter
Name
QoSCategory
Value QoSMetric
QoSWeight
Tendency
NonNumericMetricNumericMetricExactNumeric
IntervalNumeric
BooleanMetric
LinguisticMetric GradingMetric
No
HighMidLow
QoSUnit
Numeric Value
TextValue
Yes
hasvalue
hasvalue
hasvalue
hasvalue
hasvalue
endstart
hasName hasTendency
hasCategory
contains
hasWeight
hasMetric
isMeasuredIn
sameAs
28/10/2014 11
QoS Parameters for SPARQL Endpoints
hasValue
QoSProfile
QoSParameter
Name
QoSCategory
Value QoSMetric
QoSWeight
Tendency
NonNumericMetricNumericMetricExactNumeric
IntervalNumeric
BooleanMetric
LinguisticMetric GradingMetric
No
HighMidLow
QoSUnit
Numeric Value
TextValue
Yes
hasvalue
hasvalue
hasvalue
hasvalue
hasvalue
endstart
hasName hasTendency
hasCategory
contains
hasWeight
hasMetric
isMeasuredIn
sameAs
28/10/2014 11
QoS Parameters for SPARQL Endpoints
hasValue
QoSProfile
QoSParameter
Name
QoSCategory
Value QoSMetric
QoSWeight
Tendency
NonNumericMetricNumericMetricExactNumeric
IntervalNumeric
BooleanMetric
LinguisticMetric GradingMetric
No
HighMidLow
QoSUnit
Numeric Value
TextValue
Yes
hasvalue
hasvalue
hasvalue
hasvalue
hasvalue
endstart
hasName hasTendency
hasCategory
contains
hasWeight
hasMetric
isMeasuredIn
sameAs
28/10/2014 11
QoS Parameters for SPARQL Endpoints
hasValue
QoSProfile
QoSParameter
Name
QoSCategory
Value QoSMetric
QoSWeight
Tendency
NonNumericMetricNumericMetricExactNumeric
IntervalNumeric
BooleanMetric
LinguisticMetric GradingMetric
No
HighMidLow
QoSUnit
Numeric Value
TextValue
Yes
hasvalue
hasvalue
hasvalue
hasvalue
hasvalue
endstart
hasName hasTendency
hasCategory
contains
hasWeight
hasMetric
isMeasuredIn
sameAs
28/10/2014 11
QoS Parameters for SPARQL Endpoints
hasValue
QoSProfile
QoSParameter
Name
QoSCategory
Value QoSMetric
QoSWeight
Tendency
NonNumericMetricNumericMetricExactNumeric
IntervalNumeric
BooleanMetric
LinguisticMetric GradingMetric
No
HighMidLow
QoSUnit
Numeric Value
TextValue
Yes
hasvalue
hasvalue
hasvalue
hasvalue
hasvalue
endstart
hasName hasTendency
hasCategory
contains
hasWeight
hasMetric
isMeasuredIn
sameAs
28/10/2014 11
QoS Parameters for SPARQL Endpoints
hasValue
QoSProfile
QoSParameter
Name
QoSCategory
Value QoSMetric
QoSWeight
Tendency
NonNumericMetricNumericMetricExactNumeric
IntervalNumeric
BooleanMetric
LinguisticMetric GradingMetric
No
HighMidLow
QoSUnit
Numeric Value
TextValue
Yes
hasvalue
hasvalue
hasvalue
hasvalue
hasvalue
endstart
hasName hasTendency
hasCategory
contains
hasWeight
hasMetric
isMeasuredIn
sameAs
28/10/2014 11
QoS Parameters for SPARQL Endpoints
hasValue
QoSProfile
QoSParameter
Name
QoSCategory
Value QoSMetric
QoSWeight
Tendency
NonNumericMetricNumericMetricExactNumeric
IntervalNumeric
BooleanMetric
LinguisticMetric GradingMetric
No
HighMidLow
QoSUnit
Numeric Value
TextValue
Yes
hasvalue
hasvalue
hasvalue
hasvalue
hasvalue
endstart
hasName hasTendency
hasCategory
contains
hasWeight
hasMetric
isMeasuredIn
sameAs
28/10/2014 11
QoS Parameters for SPARQL Endpoints
hasValue
QoSProfile
QoSParameter
Name
QoSCategory
Value QoSMetric
QoSWeight
Tendency
NonNumericMetricNumericMetricExactNumeric
IntervalNumeric
BooleanMetric
LinguisticMetric GradingMetric
No
HighMidLow
QoSUnit
Numeric Value
TextValue
Yes
hasvalue
hasvalue
hasvalue
hasvalue
hasvalue
endstart
hasName hasTendency
hasCategory
contains
hasWeight
hasMetric
isMeasuredIn
sameAs
28/10/2014 12
QoS Parameters for SPARQL Endpoints
For QoS based ranking of the SPARQL endpoints • Identification of the various QoS parameters associated with
the SPARQL endpoints
• Semantic respresentation of the identified QoS parameters
• Extension of the existing SPARQL endpoints description vocabularies (VoID/SD) to associate QoS parameters
• Evaluation techniques for the QoS metrics
• Continuous monitoring of the SPARQL endpoints to generate QoS profiles
28/10/2014 13
Evaluation of the QoS Parameters
• Performance
• Response Time
Q1 . SELECT ?p where { <s> ?p <o> } Q2 . SELECT ?o where { s1 p1 ?o
s2 p2 ?o }
28/10/2014 14
Evaluation of the QoS Parameters
• Performance
• Response Time • Execution Time
Q1 . SELECT ?p where { <s> ?p <o> } Q2 . SELECT ?o where { s1 p1 ?o
s2 p2 ?o } Q3 . SELECT * where { ? s ?p ?o } LIMIT 1000
28/10/2014 15
Evaluation of the QoS Parameters
• Performance
• Response Time • Execution Time • Throughput
Repeated execution of Q1.
28/10/2014 16
Evaluation of the QoS Parameters
• Performance
• Response Time • Execution Time • Throughput • Error Rate
By putting the counter on the error returns by the SPARQL endpoint during the execution of the queries
28/10/2014 17
Evaluation of the QoS Parameters
• Interoperabiilty
• SPARQL Version • Additional Features • Restricted Features
• SPARQL 1.1 test data set
28/10/2014 18
Evaluation of the QoS Parameters
• Availability
• UpTime • DownTime • MeanUpTime • MTTR
• We rely on the service provider for the provision of initial UpTime.
• Periodic execution of query Q1 to monitor availability • Started the counter of DownTime whenever Q1 failed • MeanUpTime calculated as percentage of the time
SPARQL endpoint was available since its initial UpTime. • Mean Time To Recover (MTTR) is calculated as average
time taken by SPARQL endpoint to recover after failure.
28/10/2014 19
Evaluation of the QoS Parameters
• Licensing • PDDL • ODC-By • ODC-ODbL • CC0 0.1 Universal
Q6 .
PREFIX dcterms : <http://purl.org/dc/terms/> SELECT ?license WHERE { ?ds a void:Dataset . ?ds dcterms:license ?license . }
28/10/2014 20
Evaluation of the QoS Parameters
• Dataset Description • Vocabulary for Interlinking Datasets • Service Description
Q4 . PREFIX void : <http://rdfs.org/ns/void#> SELECT ?ds WHERE { ?ds a void:Dataset . ?ds void:SPARQLEndpoint
<SPRQLEnpointURI> }
28/10/2014 21
Evaluation of the QoS Parameters
• ResultSet • Size Limit • Result Format
Q5 . PREFIX sd: <http://www.w3.org/ns/sparql-service-description#>
SELECT ?format WHERE { ?s a sd:service . ?s sd:endpoint <endpointURI> . ?s sd:resultFormat ?format . }
28/10/2014 22
Evaluation of the QoS Parameters
• Data Quality
• Accuracy • Data Consistency • Completeness • Freshness
Data quality is an overlap between quality of information(QoI) and quality of service(QoS)
28/10/2014 23
QoS Parameters for SPARQL Endpoints
For QoS based ranking of the SPARQL endpoints • Identification of the various QoS parameters associated with
the SPARQL endpoints
• Semantic respresentation of the identified QoS parameters
• Extension of the existing SPARQL endpoints description vocabularies (VoID/SD) to associate QoS parameters
• Evaluation techniques for the QoS metrics
• Continuous monitoring of the SPARQL endpoints to generate QoS profiles
28/10/2014 24
Monitoring QoS metrics of SPARQL endpoints
• Montioring • Runtime • Periodic
28/10/2014 24
Monitoring QoS metrics of SPARQL endpoints
• Montioring • Runtime • Periodic
• QoS Profile Generation
28/10/2014 25
Federated SPARQL Queries
• SPARQL 1.1 extension provides SERVICE keyword • Allows remotely execution of the SPARQL queries on several
endpoints
Federated SPARQL Query Engine
Source Selection
Indexing/Caching
Query ExecutionOptimiser
SPARQLEndpoint …SPARQL
EndpointSPARQLEndpoint
SPARQLEndpoint
SPARQL
28/10/2014 26
Federated SPARQL Queries
• Problem of data source selection • Automated discovery and execution of the SPARQL endpoints
for any federated query.
Federated SPARQL Query Engine
Source Selection
Indexing/Caching
Query ExecutionOptimiser
SPARQLEndpoint …SPARQL
EndpointSPARQLEndpoint
SPARQLEndpoint
SPARQL
28/10/2014 27
Federated SPARQL Queries
• Problem of data source selection • Automated discovery and execution of the SPARQL endpoints
for any federated query.
• Candidate Data Sources: “Given a user's query Q and set of n data sources
DS = { dsi | i =1..n} , we define set of candidate data sources as
DSc = { dscj | j = 1..m } that can potentially contribute to answer query Q, where
DSc ⊆ DS and 1 ≤ m ≤ n . “
28/10/2014 28
Federated SPARQL Queries
• Problem of data source selection • Automated discovery and execution of the SPARQL endpoints
for any federated query.
• QoS Aware Data Sources: “Given a set of candidate data sources DSc, we define set of QoS aware data sources as
DSqos = { dsqosk | k = 1..l } as set of optimal data sources that can potentially contribute to the answer
of the Query Q and are compliant with the QoS requirements mentioned in the query, where DSqos ⊆ DSc and 1 ≤ l ≤ m ≤ n . “
28/10/2014 29
QoS-Aware Federated SPARQL Queries
Federated SPARQL Query Engine
QoS Aware Query Parser
Source Selection
Indexing/Caching
QoS Aware Source Selection
QoS Repository
QoS Evaluation
Query Execution
Optimiser
SPARQLEndpoint …SPARQL
EndpointSPARQLEndpoint
SPARQLEndpoint
User Query& QoS SPARQL
DSc
DSqos
QoSProfile
Monitoring
28/10/2014 29
QoS-Aware Federated SPARQL Queries
Federated SPARQL Query Engine
QoS Aware Query Parser
Source Selection
Indexing/Caching
QoS Aware Source Selection
QoS Repository
QoS Evaluation
Query Execution
Optimiser
SPARQLEndpoint …SPARQL
EndpointSPARQLEndpoint
SPARQLEndpoint
User Query& QoS SPARQL
DSc
DSqos
QoSProfile
Monitoring
28/10/2014 29
QoS-Aware Federated SPARQL Queries
Federated SPARQL Query Engine
QoS Aware Query Parser
Source Selection
Indexing/Caching
QoS Aware Source Selection
QoS Repository
QoS Evaluation
Query Execution
Optimiser
SPARQLEndpoint …SPARQL
EndpointSPARQLEndpoint
SPARQLEndpoint
User Query& QoS SPARQL
DSc
DSqos
QoSProfile
Monitoring
28/10/2014 30
SPARQL Extension with QoS
• QoS requirements can be described as part of the SPARQL query
• We introduce a new QOSREQ keyword in the SPARQL query language
• QOSREQ operator is applied to the triple pattern or BGP immediarly proceeding the operator
• Comma separated values of multiple QoS parameters within QOSREQ operator
• Comparison operators to compare the user defined QoS requirements with QoS profile of the SPARQL endpoint
28/10/2014 30
SPARQL Extension with QoS
• QoS requirements can be described as part of the SPARQL query
SELECT ?drug ?keggUrl ?chebiImage WHERE { ?drug rdf:type drugbank:drugs .
QOSREQ[ qs:ResponseTime < 10 , qs:SizeLimit > 10000] ?drug drugbank:keggCompoundId ?keggDrug . ?keggDrug bio2rdf:u r l ?keggUrl . { ?drug drugbank:genericName ?drugBankName . ?chebiDrug purl:title ?drugBankName . }
QOSREQ[ qs:DatasetDescription = 'VoID' , qs:MeanUpTime > 80 ]
?chebiDrug chebi:image ?chebiImage . }
28/10/2014 31
QoS-Aware Federated SPARQL Queries
Federated SPARQL Query Engine
QoS Aware Query Parser
Source Selection
Indexing/Caching
QoS Aware Source Selection
QoS Repository
QoS Evaluation
Query Execution
Optimiser
SPARQLEndpoint …SPARQL
EndpointSPARQLEndpoint
SPARQLEndpoint
User Query& QoS SPARQL
DSc
DSqos
QoSProfile
Monitoring
28/10/2014 31
QoS-Aware Federated SPARQL Queries
Federated SPARQL Query Engine
QoS Aware Query Parser
Source Selection
Indexing/Caching
QoS Aware Source Selection
QoS Repository
QoS Evaluation
Query Execution
Optimiser
SPARQLEndpoint …SPARQL
EndpointSPARQLEndpoint
SPARQLEndpoint
User Query& QoS SPARQL
DSc
DSqos
QoSProfile
Monitoring
28/10/2014 31
QoS-Aware Federated SPARQL Queries
Federated SPARQL Query Engine
QoS Aware Query Parser
Source Selection
Indexing/Caching
QoS Aware Source Selection
QoS Repository
QoS Evaluation
Query Execution
Optimiser
SPARQLEndpoint …SPARQL
EndpointSPARQLEndpoint
SPARQLEndpoint
User Query& QoS SPARQL
DSc
DSqos
QoSProfile
Monitoring
28/10/2014 31
QoS-Aware Federated SPARQL Queries
Federated SPARQL Query Engine
QoS Aware Query Parser
Source Selection
Indexing/Caching
QoS Aware Source Selection
QoS Repository
QoS Evaluation
Query Execution
Optimiser
SPARQLEndpoint …SPARQL
EndpointSPARQLEndpoint
SPARQLEndpoint
User Query& QoS SPARQL
DSc
DSqos
QoSProfile
Monitoring
28/10/2014 31
QoS-Aware Federated SPARQL Queries
Federated SPARQL Query Engine
QoS Aware Query Parser
Source Selection
Indexing/Caching
QoS Aware Source Selection
QoS Repository
QoS Evaluation
Query Execution
Optimiser
SPARQLEndpoint …SPARQL
EndpointSPARQLEndpoint
SPARQLEndpoint
User Query& QoS SPARQL
DSc
DSqos
QoSProfile
Monitoring
28/10/2014 31
QoS-Aware Federated SPARQL Queries
Federated SPARQL Query Engine
QoS Aware Query Parser
Source Selection
Indexing/Caching
QoS Aware Source Selection
QoS Repository
QoS Evaluation
Query Execution
Optimiser
SPARQLEndpoint …SPARQL
EndpointSPARQLEndpoint
SPARQLEndpoint
User Query& QoS SPARQL
DSc
DSqos
QoSProfile
Monitoring
28/10/2014 31
QoS-Aware Federated SPARQL Queries
Federated SPARQL Query Engine
QoS Aware Query Parser
Source Selection
Indexing/Caching
QoS Aware Source Selection
QoS Repository
QoS Evaluation
Query Execution
Optimiser
SPARQLEndpoint …SPARQL
EndpointSPARQLEndpoint
SPARQLEndpoint
User Query& QoS SPARQL
DSc
DSqos
QoSProfile
Monitoring
28/10/2014 32
Experimental Evaluation • FedBench Benchmark • A benchmark suite for federated SPARQL queries
evaluation • Provides various data sets from Life Sciences, Linked
Data and Cross Domains • 25 queries to evaluate the performance
• Testbed • Datasets are deployed as SPARQL endpoints • Multiple Copies of the data sets to create higher number of
candidate data sources • Human intervention to create fluctuation • Montioring of the SPARQL endpoints for more than 2 months • QoS Profiles generation and updates in QoS metrics values based
on continuous monitoring
28/10/2014 33
Experimental Evaluation
0"
5"
10"
15"
20"CD
1"CD
2"CD
3"CD
4"CD
5"CD
6"CD
7"LS1"
LS2"
LS3"
LS4"
LS5"
LS6"
LS7"
LD1"
LD2"
LD3"
LD4"
LD5"
LD6"
LD7"
LD8"
LD9"
LD10"
LD11"
No."of"Selected"Da
ta"Sou
rces"
FedX?QBenchmark" Splendind?QBenchmark"
QoSAware?QDefault" QoSAware?Quser"
28/10/2014 34
Experimental Evaluation
0"
5"
10"
15"CD
1"CD
2"CD
3"CD
4"CD
5"CD
6"CD
7"LS1"
LS2"
LS3"
LS4"
LS5"
LS6"
LS7"
LD1"
LD2"
LD3"
LD4"
LD5"
LD6"
LD7"
LD8"
LD9"
LD10"
LD11"
No."of"Selected"Da
ta"Sou
rces"
Q_50" Q_75" Q_100"
28/10/2014 35
Conclusion
• Identification and semantic representation of the QoS parameters of the SPARQL endpoints
• QoS metrics evaluation mechanism
• A monitoring Service for QoS Evaluation
• SPARQL extension for users QoS requirements within query language
• QoS-Aware Federated SPARQL query evaluation
28/10/2014 35
Future Work
• QoS monitoring over public SPARQL endpoints & integration with SPARQLES
• Sophisticated mechanisms for Quality of Information evaluation
• Taking QoS requirements as well preferences into account (Hard and Soft Constraints)
• QoS aggregated values