Linked Open Data (LOD)
The National Diet Library (NDL) provides metadata as Linked Open Data (LOD) to facilitate effective use by computer systems and applications. This page provides general information about NDL LOD. For information on use cases of the NDL LOD, please refer to Using Linked Open Data (LOD).
1. What is LOD?
The term Linked Open Data (LOD) refers to data which has features of both a Linked Data and an Open Data. Linked Data stands for data that is connected with other data, and Open Data is data that is freely available to anyone due to an open license.
According to Tim Berners-Lee, inventor of the World Wide Web, the use of Linked Data should follow these four principles(1).
- Use Uniform Resource Identifiers (URI)s as names for things.
- Use HTTP URIs so that people can look up those names.
- When someone looks up a URI, provide useful information, using standard formats like RDF or SPARQL.
- Include links to other URIs so that users can discover more things.
The application of these principles allows titles, authors, places, concepts, and all kinds of entities to be linked with other related entities. This helps constructing an integrated knowledge base, and enables computers to identify relationships between entities.
The volume of Linked Data published both in Japan and around the world is on the increase. At the G8 summit held on 18 June 2013, leaders of the G8 agreed to abide by the Open Data Charter, which sets out principles for releasing government data in a machine-readable and open format under open license(2).
Even prior to this development, national libraries in many countries had been providing LOD proactively(3) (4) (5). And events such as the LOD Challenge have been held in Japan and many other countries to encourage the use of LOD worldwide(6).
2. What is NDL LOD?
The NDL strives to provide the following LOD that meets the four principles described above and is open to everyone.
Bibliographic Data (NDL Search)
Data Contents
- Metadata of books, journals, articles, newspapers, digital contents (digitized materials, sounds, web pages, etc.).
- Metadata include title, author, publisher, subject matter (topics, geographic names), classifications (NDC, NDLC), ISBN, ISSN, National Bibliography No., NDL call number, and information on holding libraries such as prefectural and municipal libraries.
- Identifiers such as NDLBibID (NDL Bibliography ID) which are used to identify bibliographic data that the NDL creates and provides and NDLJP (NDL permanent identifier) which are used to identify digitized contents and archival materials of internet resources.
- URLs of webpages which show digitized content (https://dl.ndl.go.jp/...)
- Information related to copyright protection
Information on Usage of Data
| Data Sources | Databases listed in the list of the data providers (Japanese) such as National Diet Library Catalog, National Diet Library Digital Collections, digital archives provided by public and college libraries in Japan, Aozora Bunko. |
|---|---|
| Downloading Data | NDL Search provides APIs (SRU, OpenSearch, OpenURL and OAI-PMH). For details, please refer to How to use NDL Search API [PDF]. * Please refer to Free Data Service for information on data provided as open datasets. |
| Terms of Use | Depending on the purpose of using the NDL Search API, application for permission may be necessary. Details are available at How to use NDL Search API. Please apply using the Application Programming Interface (API) of the NDL Search: Application Form. |
| Terms for Data Description | National Diet Library Dublin Core Metadata Description (DC-NDL) is used for data description. For details on metadata formats, please refer to NDL(RDF) Formats Specifications (in Japanese). |
Authority data (Web NDL Authorities)
Data Contents
- Information which identifies authors who have several names (pen names, maiden names, etc.) (e.g., Natsume Soseki and Natsume Kinnosuke) as well as synonyms (e.g., climate, climatic phenomenon, and weather)
- Information which identifies different people with same names (e.g., Suzuki Ichiro, 1881–1961, and Suzuki Ichiro, 1900–1985)
- Information on synonyms which indicate a certain topic (subject matter), hypernyms, hyponyms, and related words (e.g., synonyms, such as earthquake, seismic event, and tremor; hypernyms such as natural disaster, hyponyms such as earthquake fires, and related words such as seismic activity, earthquake insurance, and disaster prevention)
- Family names (e.g., the Tokugawa clan, the Yamanouchi clan), and names of organizations (e.g., the National Astronomical Observatory of Japan, the Science Council of Japan)
- Information on geographic names (e.g., Tokyo; Chiyoda-ku, Tokyo City; Akasaka-ku, Tokyo; etc.)
- URI (Linked Data) of The Library of Congress Subject Headings (LCSH) and Virtual International Authority File (VIAF)
- Identifiers such as those assigned to authority data of personal names, family names and corporate body names, authority data of geographic names and uniform names, and authority data of topical terms and subdivisions (NDLSH).
Information on Usage of Data
| Downloading Data | Web NDL Authorities provides an API via SPARQL. Please refer to About SPARQL (Japanese) and Web NDL Authorities SPARQL API Specification [PDF] for more details. * There are two formats in Files for Batch Download: RDF/XML and TSV. These files contain authority data that will be included in National Diet Library List of Subject Headings (NDLSH) in Web NDL Authorities. * Individual authority data in RDF/XML, RDF/Turtle, or JSON-LD format can be obtained from the links shown at the bottom of the detailed information page. Please refer to Description of Functions for more details. |
|---|---|
| Terms of Use | Authority data of the Web NDL Authorities may be reused either for profit or for non-profit activities without prior application as long as Web NDL Authorities is cited as the source. Please refer to Terms of use for more details. |
| Terms for Data Description | SKOS-XL, SKOS, DC-NDL, RDFS, Dublin Core, FOAF, and OWL are used as terms for authority data descriptions. Please refer to About the RDF Model 2. Vocabulary Used in the Authority Data for more detail. |
Earthquake related data (NDL Great East Japan Earthquake Archive (nickname: "HINAGIKU"))
Data Contents
- Metadata (title, creator, publisher, date, location, summary/abstract, etc.) of photos (aerial photographs of the disaster area and photos of damage), sound recordings/videos (related to support activities for the affected areas, the Fukushima Daiichi nuclear disaster, and testimony of disaster victims, etc.)
- *ma:locationLatitude tag shows the latitude, ma:locationLongitude tag shows the longitude, and dcterms:created tag (in ndlkn:Resource class) includes the date of photos and movies.
- Metadata (title, publisher, and saved date, etc.) of old web pages (municipal governments, etc.)
- Metadata (title, creator, publisher, etc.) of books, journals, newspapers, and brochures (flyers, etc.).
- URLs of webpages that show digitized content (documents, photos, sound recordings/movies), thumbnail URLs, and URLs of webpages which shows past webpages.
Information on Usage of Data
| Data Sources | Various institutional repositories which compile records about the Great East Japan Earthquake posted on List of Data Providers and Available Metadata such as Geospatial Information Authority of Japan, Center for Remembering 3.11 (sendai mediateque), photos at the disaster area of Shinchi, Fukushima (Shinchi Town Library), ICT Project for Preserving Community Ties "Telling the Story of the Great East Japan Earthquake" (Higashimatsushima Library), aerial photographs (by Aero Asahi Corporation), and the National Diet Library Web Archiving Project (WARP). |
|---|---|
| Downloading Data | HINAGIKU provides API via SRU, OpenSearch, and OAI-PMH. Please refer to Application Programming Interface (API) for more details. |
| Terms of Use | In order to use the HINAGIKU API for commercial purposes, application for permission may be necessary. Please refer to About-API use application, fill out the required items of the "Entry of use application" and send it online to the email address shown in Inquiries. |
| Terms for Data Description | Terms of the National Diet Library Great East Japan Earthquake Archive Metadata Schema are used for data description. For details, please refer to Metadata. |
GLAM Data (Japan Search)
- *The term "GLAM" stands for galleries, libraries, archives, and museums.
Data Contents
- Metadata of contents provided via digital archived of various genres such as books, cultural heritage, art media, etc.
Information on Usage of Data
| Data Sources | Databases that provide data to Japan Search are listed under Database. Data provided by databases that are labeled "Metadata Rights (API Available)" under "Conditions" on the detailed information page is available as LOD. |
|---|---|
| Downloading Data | Japan Search provides SPARQL API, EasySPARQL, and a simple Web API. For details, please refer to For Developers of the Japan Search. |
| Terms of Use | The terms of use are different among databases that provide data to the Japan Search. For details, please refer to Site policy | Using Data. |
| Terms for Data Description | JPS-RDF Schema is used for data description. For details, please refer to An Overview of the JPS-RDF Schema. |
3. Promotion of LOD by the NDL
NDL initiatives to promote LOD include the following:
Cooperative Research Project on making Linked Data of the Nippon Decimal Classification
The Nippon Decimal Classification (NDC) is a standard classification system developed and maintained by the Japan Library Association (JLA) for the efficient management of library collections in Japan. The NDL and the JLA conducted a research project that resulted in a Linked Data version of the NDC. The cooperative research project was concluded with the briefing session to report the outcome of the project (Japanese) in July 2016.
- Term: April 2015 – March 2016
- Object: NDC 8th Edition and NDC 9th Edition
- Overview: The NDL and JLA, based on the digital data of the NDC provided by the JLA, named MRDF, conducted research on the creation of a Linked Data version of the NDC (NDC-LD). The outcome was registered as a controlled vocabulary to Metabrige, which is managed by the Metadata Information Infrastructure Initiative. Additionally, the outcome can be downloaded from the JLA website. For details, please refer to NDC data (NDC 8 and 9) (Japanese).
Beta version of International Standard Identifier for Libraries and Related Organizations (ISIL) LOD
The International Standard Identifier for Libraries and Related Organizations (ISIL) is an identifier which can be allocated to libraries and relevant organizations, such as archives and museums. The NDL provides ISIL LOD of as part of its promotion of LOD.
Cooperation with open data events and activities
The NDL cooperates with open data events and activities:
Events
The NDL hosts hackathons and related events to promote the use of data provided by the NDL. For details on past events, please refer to NDL-Lab (Japanese).
4. References
- (1)Berners-Lee, Tim. "Linked Data" Design Issues. 2009/06/18
- (2)Open Data Charter agreed at the G8 Summit Current Awareness Portal-R (2013-6-26) (Japanese)
- (3)Hideaki Takeda "The development of Linked Data" Current Awareness 2011 (308) CA1746 pp. 8-11 (Japanese)
- (4)Ikki Omukai "Open Data and Libraries" Current Awareness 2014 (320) CA1825, pp. 14-16 (Japanese)
Examples of LOD provided by national libraries in other countries are as follows:- Subject headings, classification schemes, name authority file, etc. of the Library of Congress: ID.LOC.GOV - Linked Data Service
- Bibliographic data of the British Library: The British National Bibliography as Linked Open Data
- Bibliographic data, authority data, etc. of Bibliotheque nationale de France: accueil (data.bnf.fr)
- Bibliographic data, authority data, etc. of the German National Library: DNB - Metadata Services
- Bibliographic data, thesauri, etc. of the National Library of Finland: National Library of Finland Open Data
Akiko Hashizume "Linked Open Data: Trends of European and American libraries and activities of the National Diet Library" NDL Bibliographic Data Newsletter 33 (2) 2015 (Japanese)
Tomoko Okuda, Saho Yasumatsu “Open data of national libraries: from Linked Data to large-scaled datasets for research” Libraries Today 2018 vol. 56 no.1 (Japanese) - (5)Interaction of LOD on the web displays in The Linking Open Data cloud diagram and Linked Open Data Cloud Diagram 2014. They include LOD of national libraries in many countries in addition to the NDL LOD.
- (6)LOD Challenge is a contest which commends efforts related to open database building and utilization in Japan.
Contact for inquiries about Linked Open Data (LOD)
Standardization Section, Digital Information Distribution Division,
Digital Information Department, National Diet Library
E-mail: standardization