TataKelola dan KamSiber Kecerdasan Buatan v022.pdf
Linked data enhanced publishing for special collections (with Drupal)
1. ZBW is member of the Leibniz Association
Linked Data Enhanced Publishing
for Special Collections
Joachim Neubert
ZBW – German National Library of Economics
Leibniz Information Centre for Economics
ELAG 2013
Ghent, Belgium
29.5.2013
2. Motivation
• Special collections often consist of specific (sometimes unique)
kinds of objects with special attributes (e.g., type or material,
selected from a list) which require non-standard data structures
• Custom navigation (e.g., by historical period or dynasty) is eligible
• Static pages (e.g., a “news” section, “about” or “help” pages) are
often required, too
Turn-key “standard” systems for these requirements are not
available
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3. My own background
• Scientific software developer at ZBW – German National Library for
Economics, mainly concerned with Linked Open Data and
knowledge organization systems and services
• Published 20th Century Press Archives in 2010, with some 100,000
digitized newspaper articles in dossiers (http://zbw.eu/beta/p20,
custom application written in Perl)
• Published a repository of ZBW Labs projects recently – basicly
project descriptions and a blog (http://zbw.eu/labs, Drupal based)
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4. Page 4
Further Agenda
1) Linked Data, Content Management Systems, and Drupal
2) Customizing Drupal 7 for special collections
3) Current limitations of RDF/LD support in Drupal 7
4) Outlook
7. Weaving the web of Linked Data
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http://www.worldcat.org/oclc/8281462
http://viaf.org/viaf/213505112
http://dbpedia.org/resource/Frida_Kahlo
8. Page 8
Linking Open Data cloud diagram, by Richard Cyganiak and Anja Jentzsch. http://lod-cloud.net/
9. So, why linked data enhanced publishing?
• Differentiate the subjects of your web pages and their attributes
• Thus, foster data reuse in 3rd party services and applications
• Mashups
• Search engines
• Create meaningful links, adding value for users
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10. Why use a content management system?
• Standard tasks (browser compatibility, page templates, responsive
css, site navigation, search, form handling, calendar, wysiwyg,
revisions, translations, permissions, data management , security)
made easy
• Easy-to-add web 2.0 features (blogging and comments, tags, rating,
forums, …)
• Know-how available outside a single development team
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11. Why Drupal?
• Open & modular architecture
● Extensible by modules
● Standards-based
● Scalable
• Widely used all over the world
• Vibrant open source community,
and commercial services, too
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http://drupal.org/getting-started/before/overview
http://de.slideshare.net/scorlosquet/drupal-as-a-semantic-web-platform
21. Output in RDFa
• Drupal renders RDF mappings as HTML attributes
• No frickling in HTML producing code or templates
• Works out of the box for different Drupal themes (screen designs)
• In Drupal 7, by default XHTML/RDFa 1.0
• Themes for HTML5/RDFa 1.1 available (e.g., Zen)
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22. M
<http://zbw.eu/labs/project/zbw-labs> a schema:CreativeWork,
doap:Project;
dc:description """
ZBW Labs Website is a semantically enriched directory of ZBW Labs
Projects. Labs projects range from small showcases, which may or may
not be part of a larger project, to full-fleged applications in beta
state.
The new ZBW Labs website is based on Drupal 7 and uses RDFa, which is
part of Drupal Core. Used vocabularies are Dublin Core Terms (dc),
Description of a Project (doap) und Schema.org (schema).
"""@en;
dc:subject <http://zbw.eu/labs/en/taxonomy/term/1>,
<http://zbw.eu/labs/en/taxonomy/term/11>,
<http://zbw.eu/labs/en/taxonomy/term/3>,
<http://zbw.eu/labs/en/taxonomy/term/50>;
dc:title "ZBW Labs Website"@en;
schema:name "ZBW Labs Website"@en;
[...]
doap:created "2012-04"^^xsd:gYearMonth,
"2012-04-01T00:00:00+02:00"^^xsd:gYearMonth;
doap:homepage <http://zbw.eu/labs>;
doap:name "ZBW Labs Website"@en;
doap:shortdesc "ZBW Labs projects exposed as Linked Open Data"@en;
xhv:license <http://creativecommons.org/publicdomain/zero/1.0/> .
<http://zbw.eu/labs/en/taxonomy/term/3> a skos:Concept;
rdfs:label "Publishing Technologies"@en;
skos:prefLabel "Publishing Technologies"@en . Page 22
23. Additional Linked Data / RDF features
• Serialize Drupal RDF data in RDF/XML, Turtle, NT (Modules: RDFx,
RESTful Web Services) *, JSON-LD (Modules: JSON-LD, restws)
• Expose Drupal RDF data in a SPARQL endpoint (Module: SPARQL)
• Support microdata output (Module: Microdata)
• Consume RDF data from other SPARQL endpoints and display it as
part of a Drupal site (Module: SPARQL Views)
• Add links to other Linked Data entities (Module: Web Taxonomy)
* currently does not work with PostgreSQL – for a workarround, see http://drupal.org/node/1999754#comment-7438562
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24. Web Taxonomy: Using vocabularies from the web
• Autocomplete widget for Drupal fields, powered by vocabularies
maintained elsewhere
• Prerequisites:
• a web-accessible autosuggest service which delivers terms and
their URIs (may be JSON, SPARQL results or even SOAP)
• a custom coded plugin to access the service
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25. Page 25
Plugin example: Economics Taxonomies
Code downloadable and installable from https://drupal.org/sandbox/jneubert/1447918
• Third party thesauri, such as STW Thesaurus for Economics, can be
re-used for indexing a collection
26. Extending Drupal even further
Drupal is not only a CMS, but also a Content Mangement Framework
• Well defined APIs (database abstraction layer, Field API, RDF
Mapping API, Form API, Entity API, …)
• Entity API allows building custom entities with arbitrary properties
• … even residing in remote databases
requires substantial programming skills
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28. Cool URIs require work
1) out-of-the-box default URI
http://zbw.eu/labs/en?q=node/25
2) with the „Clean URLs“ feature enabled
http://zbw.eu/labs/en/node/25
3) with the (core) „Path“ module enabled and an alias defined
http://zbw.eu/labs/en/project/zbw-labs
4) removing the language path element (en/de) in multilingual sites for
a language-independent resource URI requires custom code
http://zbw.eu/labs/project/zbw-labs
(see code example in http://groups.drupal.org/node/247058#comment-798823)
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29. Nested RDF structures only with custom code
Workarround example:
Git repository URI in DOAP ontology demands a separate node, e.g.,
<> a schema:CreativeWork, doap:Project;
doap:repository [ a doap:GitRepository;
doap:location "http://github.com/some/id.git" ];
• Create field_gitrepository and map to doap:location
• Create a custom template file for the field (field--field_gitrepository--
lproject.tpl.php)
<div rel="doap:repository" class="field-items"<?php print $content_attributes; ?>>
<div about="[_:repos]" typeof="doap:GitRepository">
<?php foreach ($items as $delta => $item): ?>
<div class="field-item"<?php print $item_attributes[$delta]; ?>><?php
print render($item); ?></div>
<?php endforeach; ?>
</div>
</div>
</div>
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30. Further limitations in Drupal 7
• RDFa support currently works for single entities – pages with multiple
entities (search results, term pages, views, etc.) are not supported
• RDFa output may break under certain special conditions
(http://drupal.org/node/1778226)
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31. Outlook to Drupal 8
• Drupal base functionalities refactored for using Symphony framework
• Aimed at an extended service-oriented architecture – design goal:
“Each piece of content gets its own URL”
(http://www.unleashedmind.com/en/blog/sun/drupal-8-the-path-forward)
• RDF module split up into a plain RDF mapping module and another
module for creating RDFa markup
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32. To sum up
• Linked data publishing via a CMS, in particular Drupal, is a valid
option
• If your data can be mapped to an essentially flat RDF data structure,
linked data can be added mostly by site builders, without much
additional effort
• Sometimes research is required on how to solve problems, and at
times glue code has to be written
• But: most of the code for your web application is already there, and is
supported by a large and helpful Open Source community
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33. Page 33
Thank you!
Joachim Neubert
ZBW – Leibniz Information Centre for Economics
j.neubert@zbw.eu
http://zbw.eu/labs
