ekaw - linked data publishing

Linked Data Publishing Ruben Taelman - @rubensworks

imec - Ghent University

1

Publishing as part of any Linked Data life cycle

Generate Publish

Validate

QueryEnhance2

Publish Query... ...

Linked Data PublishingLinked Data Interfaces

Storage

Non-technical tasks

3

Linked Data PublishingLinked Data Interfaces

Storage

Non-technical tasks

4

Linked Data provides machine-accessible data Machines can retrieve and discover data through HTTP interfaces

Machines can understand the data

5

Ways for publishing Linked Data on the Web

Data dump

1 RDF document

Linked Data document

RDF document per topic

SPARQL endpoint

Expressive query interface

6

Data dumpSimple for data publisher

Data dumps can be large (~gigabytes)

Querying only possible after downloading entire dataset

7

Linked Data documentData is available in smaller fragments, according to subject

Linked Data principle of dereferencing

“3. When someone looks up a URI, provide useful information, using the open Web standards such as RDF, SPARQL” (Hyland 2013)

Querying only possible by traversing links

8

SPARQL endpointRequires higher computational effort from server

Single point to get and expose data

Easily queryable by clients

9

How do the different interfaces relate to each other?

10

Linked Data Fragments (LDF)A uniform view on Linked Data interfaces

high client effort high server effort

Data du

mp

LD do

cumen

t

SPARQL res

ult

11

(Verborgh 2016)

A big unexplored area on the LDF axis

high client effort high server effort

Data du

mp

LD do

cumen

t

SPARQL res

ult

?

12

(Verborgh 2016)

Triple Pattern Fragments (TPF),a trade-off between server and client effort

high client effort high server effort

Data du

mp

LD do

cumen

t

SPARQL res

ult

TPF

13

(Verborgh 2016)

Triple Pattern FragmentsLow-cost server interface

Fragmentation of a dataset by triple patterns

Client-side SPARQL query evaluation using a TPF interface

14

Choosing an LD interface as trade-off between server and client effort

15

URI policies for interfacesLinked Data uses URI’s as a global identification system

URI design principles also apply to interface URI’s:Persistent URI’s and redirectionDomain authority (e.g. government domain)Machine and human-readable representations through content negotiation...

16

Linked Data PublishingLinked Data Interfaces

Storage

Non-technical tasks

17

Interface and storage solution influence each other

18

Start with most restrictive elementStorage is fixed → storage, interface

Machine limitations → interface, storage

19

Storage solutions for Linked Data interfacesData dump

Linked Data document

Triple Pattern Fragments

SPARQL endpoint

RDF file, HDT, ...

Static or dynamic RDF files

RDF file, HDT, SPARQL engine, ...

SPARQL engine

20

Linked Data PublishingLinked Data Interfaces

Storage

Non-technical tasks

LicensingPublication announcementMaintenance

21

Linked Open Data requires an open licenseAll published data should have a connected license

Features of openness: (Open Knowledge Foundation)

Availability and accessReuse and redistributionUniversal participation

Popular open license: CC0

Mention license in dataset listings and in metadata

Confidential data might require restrictive license and security

22

Announcing to the publicCommunication channels: mailing lists, blogs, newsletters, …

Feedback channel: form or contact address for any issues

Centralized repositories (e.g. https://datahub.io)

Automated discovery with metadata (e.g. DCAT, VOID)

23

Linked Data Publication is a continuous processSocial contract with data consumers

Avoid dataset / interface removal

Data can change

Movement of dataset to new location → URI persistence!

Responsible entity behind feedback channel

24

Linked Data PublishingLinked Data Interfaces

Storage

Non-technical tasks

25

ConclusionsDifferent Linked Data interfaces exist for publishing Linked Data

Trade-off between server and client effort

Interface and storage solution influence each other

Properly license, announce and maintain your data

26

SourcesR Verborgh “Linked Data Publishing” http://rubenverborgh.github.io/WebFundamentals/linked-data-publishing/

Hyland B, Atemezing G, Villazón-Terrazas B. “Best Practises for Publishing Linked Data”https://www.w3.org/TR/ld-bp/

Berners-Lee, Tim. "Linked data, 2006." (2006). https://www.w3.org/DesignIssues/LinkedData.html

Villazón-Terrazas, Boris, et al. "Methodological guidelines for publishing government Linked Data." Linking government data. Springer New York, 2011. 27-49.

27