Describes Linked Open Services and the basis of Linked Open Processes, as presented at the Future Internet Symposium 2010

1. KIT – University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association
KARLSRUHE SERVICE RESEARCH INSTITUTE (KSRI)
INSTITUTE OF APPLIED INFORMATICS AND FORMAL DESCRIPTION METHODS (AIFB)
www.ksri.kit.edu
SEMANTIC TECHNOLOGIES INSTITUTE (STI)
Leopold-Franzens-Universität Innsbruck
Towards Linked Open Services
and Processes
Reto Krummenacher, Barry Norton, Adrian Marte

2. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Overview
 Motivation and State-of-the-Art
 Linked Open Services Principles
 Towards Linked Open Services
 Wrapping Services
 Exposing Dynamic Linked Data Resources
 Composition of Linked Open Services
 Conclusions

3. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Services That Communicate RDF
 Semantic Web service reside at the semantic level
 Services could communicate by publishing and reading data
 Conclusion: Services should be able so share semantic data
 Services do not communicate semantic data
 Semantic Web services require ‘magic’ lifting and lowering
 Conclusion: Services should communicate semantic data
Motivation
Enable not only service processing but open service
communication at the semantic level without ‘magic’
lifting and lowering!

4. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Services That Publish Dynamic Linked Data
 Dominating format is still XML, and also JSON or YAML
 Many service on top of linked data to not expose linked data
 Conclusion: Service over linked data should offer linked data

5. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Linked Data
04.08.2010

6. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Services Over Linked Data
 A problem with the Linked Data
cloud when it comes to
services/APIs/functionalities
 The standards are often not
then used
 The results of service
interaction do not contribute to
the Linked Data cloud
 Developers have to work with
heterogeneous representations
04.08.2010

7. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Services That Publish Dynamic Linked Data
 Dominating format is still XML, and also JSON or YAML
 Many service on top of linked data to not expose linked data
 Conclusion: Service over linked data should offer linked data
 Service over linked data do not contribute to linked data
 Service (unnecessarily) leave the linked data cloud
 Conclusion: Services should remain in and contribute to
linked data
Motivation
Enable services to become contributors to the linked
data cloud and to the global knowledge base!

8. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Linked (Open) Data Principles
 Linked Data Principles:
1. Use URIs as names for things
2. Use HTTP URIs so that people can look up those names.
3. When someone looks up a URI, provide useful
information, using the standards (RDF*, SPARQL)
4. Include links to other URIs. so that they can discover
more things.
 Small and simple set of standards!
04.08.2010

9. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Linked Open Services Principles
 Not just a small and simple set of standards but
familiar to LOD workers and users…
 Four principles
Geospatial Linked Open Services
Barry Norton and Reto Krummenacher
20.09.2010

10. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Linked Open Services Principles
Describe services as LOD prosumers with
input and output descriptions as SPARQL
graph patterns
Geospatial Linked Open Services
Barry Norton and Reto Krummenacher
20.09.2010
1

11. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Linked Open Services Principles
Communicate RDF by RESTful content
negotiation
Geospatial Linked Open Services
Barry Norton and Reto Krummenacher
20.09.2010
2

12. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
LOS Principle 2
GET
Accept: text/html
303 REDIRECT /page
GET
Accept:
application/rdf+xml
(or text/n3)
303 REDIRECT /data
LinkedDataLinkedService
GET /weather
Accept:
application/rdf+xml
(or text/n3)
200 <rdf:Description>
Geospatial Linked Open Services
Barry Norton and Reto Krummenacher
20.09.2010

13. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Linked Open Services Principles
Include the implicit knowledge contribution
that results from interactions in service
descriptions and communications
Geospatial Linked Open Services
Barry Norton and Reto Krummenacher
20.09.2010
3

14. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Linked Open Services Principles
When wrapping non-LOS services, extend the
(lifted, if non-RDF) message to make explicit
the implicit knowledge, and to use Linked
Data vocabularies, using SPARQL
CONSTRUCT queries
Geospatial Linked Open Services
Barry Norton and Reto Krummenacher
20.09.2010
4

15. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Linked Open Services
 Linked Open Services aim at promoting this style of services
 RESTful services (respecting Web architecture
 Manipulation via HTTP verbs: GET, PUT, PATCH, POST,
DELETE
 Negotiate representations
 Linked data
 Uniform use of URIs
 Use of RDF and SPARQL

16. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Linked Open Services
Geospatial Linked Open Services
Barry Norton and Reto Krummenacher
20.09.2010

17. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Towards Compositions
 Linked data, Semantic Web pipes and mash-ups integrate
(static) data sources in evolutionary fashion
 Linked Open Services (may) expose dynamic/computation-
based data sets
 Linked Open Services are addressable RDF resources
 Integration of linked data and computation-based RDF data
 Mash-ups with real-world side-effects
Geospatial Linked Open Services
Barry Norton and Reto Krummenacher
20.09.2010

18. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Linked Open Process Principles
 In order to realize Linked Open Services compositions, we
suggest the following principles:
1. Decide control flow conditions based on SPARQL ASK
queries
2. Base iteration on SPARQL SELECT queries with ORDER
BY
3. Define dataflow/mediation based on SPARQL
CONSTRUCT queries
 Again, use the languages/technologies most familiar to the
Linked Data community!
04.08.2010

19. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Linked Open Service
Composition of Linked Open Services
Web service
Service
‘Lifting’‘Lowering’
GPin
GPout
Expose a Web service, as Linked Open Service

20. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Linked Open Service
Composition of Linked Open Services
GPin
GPout
Implementation details are LOS business
‘Lifting’‘Lowering’

21. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Activity
Composition of Linked Open Services
GPin
GPout
consum
e(G
Pin)
produce(GPout)
Linked Open Service
Activity takes on the knowledge maintenance of a LOS
Keep track of the implicit knowledge shared
between the input and output

22. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Activity
Composition of Linked Open Services
GPin
GPout
consum
e(G
Pin)
produce(GPout)
Linked Open Service
Process Space / Linked Data
Process knowledge is shared amongst atomic services

23. Karlsruhe Service Research Institute
www.ksri.kit.edu
Semantic Technologies Institute
www.sti2.at
Summary
 Linked Open Services and their compositions
 Principles based on a small and simple set of standards, and
familiar to linked data workers and users
 Enable services to become contributors to the linked data
cloud and to the global knowledge base!
 Enable not only service processing but open service
communication at the semantic level without ‘magic’ lifting and
lowering!
Geospatial Linked Open Services
Barry Norton and Reto Krummenacher
20.09.2010