towards long-term preservation of linked data - the prelida project

www.sti-innsbruck.at © Copyright 2008 STI INNSBRUCK www.sti-innsbruck.at

Towards long-term preservation of linked data

The PRELIDA project

Dieter Fensel & José M. García11th April 2014 – EOD Conference, Innsbruck

www.sti-innsbruck.at 2

Short biographies

• Univ.-Prof. Dr. Dieter Fensel– Professor at the University of Innsbruck, Austria– Director of Semantic Technology Institute (STI) Innsbruck– Scientific director and coordinator of more than 70 ICT & IST projects

• Dr. José María García– University assistant (Postdoc) at the University of Innsbruck, Austria– Senior researcher at STI Innsbruck– Participation in several national and EU-funded projects, including WP

leadership in PRELIDA and BYTE

• STI Innsbruck (www.sti-innsbruck.at) – A leading institute for semantic technologies– Established in Innsbruck, Tyrol, in August 2002, initially as a “Next Web

Generation” research group at the University of Innsbruck

– Possesses strong links to local start-ups and SMEs, especially in the areas of tourism and online marketing

– Participating in PRELIDA in roadmapping, scientific events organization and dissemination leaders

http://www.sti-innsbruck.at/

www.sti-innsbruck.at

Outline

• Public Open Data

• Linked (Open) Data

• PRELIDA: Digital Preservation Linked Data

• What Digital Preservation community can provide

• What Linked Data community needs

• Outlook

3


Public Open Data

OpenData


Public Open Data: What is Open Data?

5

Definitions:

• Open data is non-personally identifiable data produced in the course of an organisation’s ordinary business, which has been released under an unrestricted licence (like the Open Government Licence).

• Open public data is underpinned by the philosophy that data generated or collected by organisations in the public sector should belong to the taxpayers, wherever financially feasible and where releasing it won’t violate any laws or rights to privacy (either for citizens or government staff).

[linkedgov project]http://linkedgov.org

http://linkedgov.org/


Public Open Data: Features of Open Data

Open Data principles [1]:

1. completeness – all data that can be open (w.r.t. privacy and security) should be open

2. primary source – all open data should be gathered at their source in raw format

3. temporal closeness – all open data should be up-to-date

4. easy access – all open data should be easily accessible

5. machine readability – all open data should be structured for machine processing

6

[1] Source [Kaltenböck M., Thurner T., (Hg.): Open Government Data Weißbuch, 2011]


Public Open Data: Features of Open Data

Open Data principles [1]:

6. non-discriminating – all open data should be accessible for everyone

7. open standards – all open data should use open standards

8. liberal licensing – all open data should use a liberal licensing without huge obligations for potential users

9. durability – all open data should be available on a long term basis

10. non-discriminating usage costs – some open data might involve usage costs. These should be kept as low as possible.

7

[1] Source [Kaltenböck M., Thurner T., (Hg.): Open Government Data Weißbuch, 2011]


Public Open Data

• Openness: Open Data is about changing behaviour

• Heterogeneity: Different vocabularies are used

• Interlinking: Need to link these data sets to prevent data silos

• Linked Open Data

8


Linked (Open) Data


Motivation: From a Web of Documents to a Web of Data

• Web of Documents• Fundamental elements:1. Names (URIs)

2. Documents (Resources) described by HTML, XML, etc.

3. Interactions via HTTP

4. (Hyper)Links between documents or anchors in these documents

• Shortcomings:– Untyped links– Web search engines fail on complex queries

“Documents”

Hyperlinks



• Web of Documents• Web of Data

“Documents”“Things”

Hyperlinks

Typed Links



• Characteristics:– Links between arbitrary things (e.g., persons, locations, events,

buildings)– Structure of data on Web pages is made explicit– Things described on Web pages are named and get URIs– Links between things are made explicit and are typed

• Web of Data

“Things”

Typed Links


Google Knowledge Graph

• “A huge knowledge graph of interconnected entities and their attributes”.

Amit Singhal, Senior Vice President at Google

• “A knowledge based used by Google to enhance its search engine’s results with semantic-search information gathered from a wide variety of sources”

http://en.wikipedia.org/wiki/Knowledge_Graph

• Based on information derived from many sources including Freebase, CIA World Factbook, Wikipedia

• Contains about 3.5 billion facts about 500 million objects

13

http://en.wikipedia.org/wiki/Knowledge_Graph


Google Knowledge Graph

14


Linked Data – a definition and principles

• Linked Data is about the use of Semantic Web technologies to publish structured data on the Web and set links between data sources.

15

Figure from C. Bizer


Linked Data – a definition and principles

1. Use URIs as names for things.

2. Use HTTP URIs so that people can look up (dereference) 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.


5-star Linked (Open) Data

★ Available on the web (whatever format) but with an open license, to be Open Data

★★ Available as machine-readable structured data (e.g. excel instead of image scan of a table)

★★★ as (2) plus non-proprietary format (e.g. CSV instead of excel)★★★★ All the above plus, Use open standards from W3C (URIs, RDF and SPARQL) to identify things, so that people can point at your stuff

★★★★★ All the above, plus: Link your data to other people’s data to provide context


LOD Cloud May 2007

Figure from http://linkeddata.org/

http://linkeddata.org/


LOD Cloud May 2007

Basics:The Linked Open Data cloud is an interconnected set of datasets all of which were published and interlinked following the Linked Data principles.

Facts:• Focal points:

• DBPedia: RDFized vesion of Wikipiedia; many ingoing and outgoing links

• Music-related datasets• Big datasets include FOAF, US Census data• Size approx. 1 billion triples, 250k links




LOD Cloud September 2011




LOD Cloud September 2011

Facts:• 295 data sets• Over 31 billion triples• Over 504 billion RDF links between data

sources




Challenges ahead

• Data economy– Non tangible assets (i.e. data) play a significant role in the creation of economic

value– Data generates the potential for many new types of product of services– Sustainability of services depends on availability of data

• Linked Data community– needs to preserve the data

• Digital Preservation community– needs Linked Data for metadata– faces new challenges by Linked Data

• So far, little or no interaction between the two communities


The PRELIDA project


PRELIDA

• PREserving LInked DAta

• EU-funded Coordination and Support Action (FP7)

• Running from 01/2013 to 12/2014

• Consortium– Consiglio Nazionale delle Richerche– Alliance for Permanent Access– University of Huddersfield– Universität Innsbruck, STI Innsbruck– Europeana Foundation– STI International


PRELIDA – Objectives

Bridge the Linked Data and Digital Preservation communities for

• making the LD community aware of the existing DP results

• making the DP community aware of the challenges posed by LD– intrinsic features of Linked Data, including their structuring, interlinking, dynamicity

and distribution.


PRELIDA – Objectives

• collect, organize and publish use cases related to the long-term access to LD

• create a comprehensive state of the art on LD and DP technologies

• set up a technology observatory

• bring together scientists and stakeholders for identifying relevant challenges and paths for addressing them in the near future

• draw attention of standardization bodies


PRELIDA – Next event

More info at http://summerschool2014.eswc-conferences.org/

• PRELIDA / ESWC Summer School• Featuring specific track for Digital

Preservation of Linked Data• From 1st to 6th September 2014• Venue: Kalamaki, Crete, Greece

• Application is now open!• Deadline: June 20th

• Several grants available

http://summerschool2014.eswc-conferences.org/



What Digital Preservation community can provide


Digital Preservation - definition

• “Digital preservation refers to the series of managed activities necessary to ensure continued access to digital objects for as long as necessary”

Neil Beagrie and Maggie Jones: “Preservation management of digital materials: The Handbook” (Digital Preservation Coalition, 2008)

• “The goal of digital preservation is, hence, the accurate rendering of authenticated content over time”

Wikipedia

• “The act of maintaining information, Independently Understandable by a Designated Community, and with evidence supporting its Authenticity, over the Long Term”

Open Archival Information System (OAIS)


OAIS Reference model


Digital Preservation - some solutions

• Use file formats based on standards

• Use services of digital archives to store documents for the long-term

• Create and maintain high quality documentation

• Use multiple storage facilities (the LOCKSS -Lots Of Copies Keeps Stuff Safe- method)


Web archiving – Internet Archive (archive.org)


Web archiving – National Libraries


Digital Preservation – topics relevant for LD

• Object classification and validation– Rendered vs non-rendered– Complex vs simple– Dynamic vs static– Active vs passive

• Representation information (representation network)– The information model is key– Recursion ends at KNOWLEDGEBASE of the

DESIGNATED COMMUNITY (this knowledge will

change over time and region)– Does not demand that ALL Representation Information

be collected at once– A process which can be tested

• Persistent identifiers• Audit & Certification / Trustworthy Digital Repositories


What Linked Data community needs


Particularities of Linked Data

• Differences between Linked Data and other types of data with respect to Digital Preservation requirements

– Is it only about reliable storing RDF data?

• Is LD preservation a special case of Web archiving?• Differences with other special types of data (e.g. multimedia content)• Functionality on top of RDF dataset (e.g. SPARQL endpoints, inference)

– Must be also preserved?

• Evolving data– Versioning– Other datasets directly or indirectly connected

• Particularities of LD may complicate preservation requirements in terms of stakeholders, rights over data, ownership of an interlinked dataset and ownership of the archived version


Challenges ahead on LD preservation (I)

• Selection of LD sources– Which data sources should be preserved?– When we stop crawling? -> Same as Web Archival?

• Who is responsible for the preservation?• Which formats can we distinguish?• Database approach• What about Linked Data which is not Open?

– Rights and licenses is the main difference, preservation-wise

• Ownership and authenticity


Challenges ahead on LD preservation (II)

• Storage– Multiple redundancy to reduce risks– Trust– Scalability (as in Web archival)

• Metadata and definitions– Self-descriptiveness requires preserving the ontologies too– Provenance and additional information


Outlook


Digital preservation Linked Data

• Ultimately, both communities can benefit from each other

• Digital preservation using Linked Data– Archival metadata

• Linked Data preservation– Storage redundancy– Archiving data– Retrieving functionality– Many other challenges to cover

• 5-star Preservable Linked Data– Outcome of PRELIDA midterm workshop of last week– Upcoming report to be published


PRELIDA Roadmap

• Gap analysis and consolidated state-of-the-art

• Defining a roadmap for long-term preservation of Linked Data

• PRELIDA Summer School– 1st-6th September 2014– Kalamaki, Crete, Greece– More info at http://summerschool2014.eswc-conferences.org/

• Final PRELIDA workshop– October 2014– Location TBD (tentatively co-located with ISWC 2014 in Riva del Garda, Italy)

• Stay tuned at http://www.prelida.eu and @PRELIDA_project (Twitter)



http://www.prelida.eu/


Thanks for your attention

Any questions?

PRELIDA is co-funded by the EU Commission under FP7 grant no. 600663

towards long-term preservation of linked data - the prelida project

Technology

public open data open

open public data

open data prelida

data sources

structured data

data silos

identifiable data

data sets