4. The step forward (With Further Readings)
4.1 Implementation Options
For anyone who is contributing to an open bibliographic data repository and considering preparing LOD-enabled bibliographic data, LODE-BD has provided recommendations on the issues related to processes and strategies. LODE-BD addressed these questions: 1. What kinds of entities and relationships are involved in describing and accessing bibliographic resources? 2. What properties should be considered for publishing meaningful/useful LOD-ready bibliographic data? 3. What metadata terms are appropriate in any given property when producing LOD-ready bibliographic data from a local database? In Section 2, General Recommendations, LODE-BD presents nine groups of common properties identified by LODE-BD and the selected metadata terms to be used for describing bibliographic resources. In Section 3, The Decision Trees, LODE-BD demonstrates how to make decisions on selecting recommended properties according to the local needs.;
After metadata terms are selected based on the flowcharts provided in the previous sections, a data provider should have come up with a list of the metadata terms that are appropriate for its existing bibliographic data. To implement these metadata terms, LODE-BD shares two options that have been summarized based on the best practices.
- Option #1, "Design-time" strategy: The data provider would need to change its current ad-hoc model, replacing it with the LODE-BD “good practices” model and those selected metadata terms. This means some changes to a database and the services that access it.
- Option #2, "Run-time" strategy: The data provider would keep the original ad-hoc model and database structure. A data provider would convert bibliographic data on the fly to a “good-practices” model upon request. This means to add a conversion service and leave the ad-hoc model unchanged.
Turning the bibliographic data from an ad-hoc modeled database in a silo to the data in a standardized metadata repository, it is a giant leap because the unified data records from various data providers can be maximized in searching and browsing through the services of the repository. Furthermore, the same practice could also lead to a step heading to the LOD universe. The individual data providers can directly produce RDF triples using LODE-BD recommended metadata terms. Or, this mission can be accomplished through the metadata repository, which would publish its bibliographic data as Linked Data, as illustrated in the following figure. In both outcomes, preparing LOD-ready metadata by data providers is essential.
Figure 2. Output of LOD-Ready Metadata
4.2 How to publish and consume Linked Data
Linked Data: Evolving the Web into a Global Data Space (1st edition), Tom Heath and Christian Bizer (2011). Synthesis Lectures on the Semantic Web: Theory and Technology, 1:1, 1-136. Morgan & Claypool.
"This book gives an overview of the principles of Linked Data as well as the Web of Data that has emerged through the application of these principles. The book discusses patterns for publishing Linked Data, describes deployed Linked Data applications and examines their architecture."
Linked Data Patterns, Leigh Dodds and Ian Davis. (2011).
"A pattern catalogue for modelling, publishing, and consuming Linked Data."
Linked Open Data star scheme by example
"Tim Berners-Lee suggested a 5-star deployment scheme for Linked Open Data and Ed Summers provided a nice rendering of it."
Linked Data - Design Issues, Tim Berners-Lee (2006).
One of the first discussions of the topic, mentioning the "four rules of Linked Data".
Cool URIs for the Semantic Web. Leo Sauermann and Richard Cyganiak (2008). W3C Interest Group Note.
4.3. Where to find Linked Data sets and Vocabularies
CKAN Data Hub
CKAN is a metadata registry for datasets. Many of the datasets described in CKAN are in linked-data form. The datasets are described by curators regarding their dataset size, example resources and access methods (e.g. SPARQL endpoints) and, crucially, links to other datasets.
Linked Open Data Cloud
URL of the LOD Cloud diagram (2014-08-30 version):
SVG image (interative): http://lod-cloud.net/versions/2014-08-30/lod-cloud_colored.svg
Library Linked Data Incubator Group: Datasets, Value Vocabularies, and Metadata Element Sets, W3C Incubator Group Report 25 October 2011
A side delivery of the W3C Linked Library Data (LLD) XG which lists relevant metadata element sets, value vocabularies that are reported in the Linked Library Data use cases and case studies. Each entry contains link URL, namespace, and short description.
Linked Open Vocabularies (LOV)
A dataset of descriptions of RDFS vocabularies or OWL ontologies defined for and used by LD datasets.
4.4. How to express metadata with different syntaxes: text, html. xml, rdf, and rdfa
DC-TEXT [DCMI Recommendation]. "Expressing Dublin Core metadata using the DC-Text format"
Its primary use is in presenting metadata constructs for human consumption.
DC-HTML [DCMI Recommendation]. "Expressing Dublin Core metadata using HTML/XHTML meta and link elements"
It describes how a Dublin Core metadata description set can be encoded using the HTML/XHTML <meta> and <link> elements. This specification is also an HTML "meta data profile" as defined by the HTML specification.
DC-DS-XML [DCMI Proposed Recommendation]. "Expressing Dublin Core Description Sets using XML (DC-DS-XML)"
It specifies an XML format for representing a Dublin Core metadata description set.
DC-RDF [DCMI Recommendation]. "Expressing Dublin Core metadata using the Resource Description Framework (RDF)"
It describes how constructs of the DCMI Abstract Model may be expressed in RDF graphs.
User Guide/ Publishing Metadata.
How to use DCMI Metadata as linked data.”
Linked Data Tutorial NG - Publishing and Consuming Linked Data Embedded in HTML, Michael Hausenblas and Richard Cyganiak.
"This document provides guidelines for how to create and consume Linked Data embedded in HTML."
4.5. Why publish bibliographic data as Linked Data?
Library Linked Data Incubator Group Final Report, W3C Incubator Group Report 25 October 2011.
- Benefits of the Linked Data Approach
This version is based on LODE-BD 1.1 that was partially supported by the European Commission through the ICT PSP Grant #250525 for VOA3R (Virtual Open Access Agriculture & Aquaculture Repository: Sharing Scientific and Scholarly Research related to Agriculture, Food, and Environment).
The authors also would like to thank Ioannis N. Athanasiadis, Nikos Manouselis, Ilias Hatzakis, Tom Baker, Gordon Dunsire, Hugo Besemer, Fernanda Peset, Xavier Agenjo, Francisca Hernández, MacKenzie Smith, Karen Coyle, Antoine Issac, the FAO AIMS Group, and the data providers of the VOA3R team for their support and advice throughout the completion of this project, as well as Laurence Skirvin who assisted in the compiling of the crosswalk to schema.org in the added appendix 4. The authors also want to thank Gordon Dunsire especially for his continuing advising on the current LODE-BD 2.0 version.