Towards Linked Open Services and Processes

KIT – University of the State of Baden-Württemberg andNational 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

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



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

MotivationEnable not only service processing but open service communication at the semantic level without ‘magic’

lifting and lowering!



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



Linked Data

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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

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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

MotivationEnable services to become contributors to the linked

data cloud and to the global knowledge base!



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!

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Not just a small and simple set of standards but

familiar to LOD workers and users…

Four principles

Geospatial Linked Open ServicesBarry Norton and Reto Krummenacher

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Describe services as LOD prosumers with input and output descriptions as SPARQL

graph patterns


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1




Communicate RDF by RESTful content negotiation


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2



LOS Principle 2

GETAccept: text/html

303 REDIRECT /page

GETAccept: application/rdf+xml (or text/n3)

303 REDIRECT /data Link

ed

Dat

aLi

nked

S

ervi

ce

GET /weatherAccept: application/rdf+xml(or text/n3)

200 <rdf:Description>


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Include the implicit knowledge contribution that results from interactions in service

descriptions and communications


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3




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


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4



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



Linked Open Services


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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


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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!

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Linked Open Service


Web service

Service

‘Lifting’‘Lowering’

GP

in

GP

out

Expose a Web service, as Linked Open Service



Linked Open Service


GP

in

GP

out

Implementation details are LOS business

‘Lifting’‘Lowering’



Activity


GP

in

GP

out

cons

ume(

GPin

) 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



Activity


GP

in

GP

out

cons

ume(

GPin

) produce(GPout)

Linked Open Service

Process Space / Linked Data

Process knowledge is shared amongst atomic services



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!


20.09.2010

Technology

Towards Linked Open Services and Processes