datos.bne.es: a Library Linked Data Dataset

Transcription

1 Undefined (2012) IOS Press datos.bne.es: a Library Linked Data Dataset Daniel Vila-Suero a, Boris Villazón-Terrazas a and Asunción Gómez-Pérez a a Ontology Engineering Group, Facultad de Informática, Universidad Politécnica de Madrid, Spain {dvila,bvillazon,asun}@fi.upm.es Abstract. In recent years, the amount semantically structured knowledge available on the Web as part the so-called Linked Open Data (LOD) cloud has seen a substantial growth in the domain cultural heritage and particularly in digital libraries. Indeed, libraries, museums and archives are showing great interest in publishing their data as Linked Data (LD). This paper presents the main characteristics one these initiatives, the recently published LD dataset from the National Library Spain. Keywords: Linked Open Data, Bibliographic Data, Authority Data, RDF 1. Introduction In recent years, the amount semantically structured knowledge available on the Web as part the so-called Linked Open Data (LOD) cloud has seen a substantial growth in the domain cultural heritage and particularly in digital libraries. Indeed, libraries, museums and archives are showing great interest in publishing their data as Linked Data (LD). Several national libraries for example have started to publish metadata as Linked Data, including the Swedish National Library 1, the German National Library 2, the National Library France 3 and the British Library 4. With Europeana 5 and VIAF 6 (Virtual International Authority File) at the forefront, there are many good examples involving important organizations and initiatives within the cultural heritage and particularly the library domain that stress the opportunities fered by Linked Data, e.g. the Stanford Linked Data Workshop (which produced the Stanford Manifesto 7 ), the Library DigitaleDienste/LinkedData/linkeddata_node. html LinkedDataWorkshop.pdf Congress (which initiated a new Linked Data-based bibliographic framework 8 ), and the Conference European National Libraries 9 (CENL) (which has decided to support open data and promote the reuse using the LD approach). The benefits publishing library data as Linked Data have been recently summarized 10 by the W3C Incubator Group on Linked Library Data (W3C LLD XG). In particular, the following key benefits LLD have been identified: i) it provides enhanced and more sophisticated navigation through cultural and heterogeneous information, ii) it increases the visibility cultural data, iii) it supports easier integration cultural information and digital objects into research documents and bibliographies, iv) it fers a more durable and robust semantic model than metadata formats that rely on specific data structures, v) it facilitates re-use across cultural heritage datasets, thus enriching the description materials with information coming from outside the organization s local domain expertise, and vi) it allows developers and vendors to avoid being tied to library-specific data formats (e.g. MARC 11 (MAchine Readable Cataloging), Z ). 8 framework html XGR-lld/ /12/$00.00 c 2012 IOS Press and the authors. All rights reserved

2 2 Vila-Suero, Villazón-Terrazas, and Gómez-Pérez / datos.bne.es: a Library Linked Data Dataset In this context, at the end 2011, the BNE has transformed into RDF and linked the catálogo de autoridades y bibliográfico (Authority and Bibliography catalogue) that contains around 7 million authority and bibliographic records. BNE authors and publications are directly linked to resources in other datasets: VIAF, DBPedia, SUDOC, LIBRIS, and the GND (the authority file from the German National Library). datos.bne.es contains approximately 58 million triples generated from MARC 21 records in Spanish and 587,000 links to other resources in multiple natural languages (e.g. German, French, English, Swedish). The following sections provide a description key features this dataset and attempt at providing a guide for potential data consumers. 2. datos.bne.es datos.bne.es is one the main results from the project Linked Data at the BNE, supported by the National Library Spain (Biblioteca Nacional de España, BNE) in cooperation with the Ontology Engineering Group (OEG) at the Universidad Politécnica de Madrid (UPM). The published dataset is the result more than one year joint-collaboration and represents one the biggest contributions high-quality RDF data in Spanish to the LOD cloud. The following points discuss the main characteristics the datos.bne.es dataset Source data The dataset is the result transforming a set MARC 21 records from the National Library Spain catalogue. This set records is composed by authority 13 and bibliographic 14 records. More specifically, the last version the dataset is the result transforming: Around 4,200,000 authority records: These records contained metadata describing people, corporate bodies, conferences, work titles, and subject headings. Around 2,400,000 bibliographic records: These records conform a representative subset the BNE catalogue, and provide metadata belong- 13 Records that conform to the MARC 21 format for authority data, see see 14 Records that conform to the MARC 21 format for bibliographic data, see ing to modern and ancient monographs, electronic records, manuscripts, periodical publications, maps, engravings, photographs, printed music, sound and audiovisual recordings. More information about the characteristics the source data, as well as links to the BNE catalogue, can be found in the datos.bne.es portal 15. Regarding the transformation process from the MARC 21 formats to RDF, the OEG has developed MARiMbA, a tool that supports the mapping process and allows librarians to use a combination RDF- S/OWL vocabularies their choice to model the data. The tool performs a pre-processing step that generates a set spreadsheets, based on the source records, that function as mapping templates where the librarians can map the different MARC metadata elements to appropriate RDFS/OWL classes and properties. A more detailed description the mapping process can be found in the short article Linked Data at the Spanish National Library and the Application IFLA RDFS Models" Modelling IFLA-backed 17 ontologies, widely agreed upon by the library community, have been used to represent the resources in RDF. Datos.bne.es is one the first international initiatives to thoroughly embrace the ontologies developed by IFLA, namely FRBR 18 (Functional Requirements for Bibliographic Records) [3], FRAD 19 (Functional Requirements for Authority Data) [2], FR- SAD 20 (Functional Requirements for Subject Authority Data) [4], and ISBD 21 (International Standard for Bibliographic Description) [5]. The first version the datos.bne.es dataset has focused on reusing as many standard and widely used vocabularies as possible, thus a network ontologies has been created by reusing several vocabularies. The core the ontology network is formed by the following classes from the FRBR ontology: (1) Per DatosEnlazados/FuentesDatos/ 16 scatn/scat-news-35.pdf 17 International Federation Library Associations and Institutions 18 er 19 <

3 Vila-Suero, Villazón-Terrazas, and Gómez-Pérez / datos.bne.es: a Library Linked Data Dataset 3 frad ELEMENTS frad Class :PERSON is subordinate ObjectProperty :CORPORATE BODY DatatypeProperties is creator is created by is realized through is realized by is realizer is part :WORK :EXPRESSION is realization has subject is subject is part is embodied in is embodiment frsad:thema frsad PREFIXES : frad : frsad: isbd: :MANIFESTATION isbd Fig. 1. Overview the ontology network Table 1 Classes and number instances within the datos.bne.es Label URI Count Manifestation 2,390,103 Work 1,969,526 Person 1,163,764 Expression 1,114,719 Thema 49,7644 Corporate Body 28,2879 son, (2) Corporate body, (3) Work, (4) Expression, and (5) Manifestation. Also, the class Thema from the FRSAD ontology has been used to model the subject authority data. Additionally, datatype, object and annotation properties have been reused from a number vocabularies, namely ISBD, RDA (Resource Description and Access) Group Elements 2 22 and Rela tionships for WEMI 23, Dublin Core terms 24, SKOS 25, MADS/RDF 26. To summarize, Figure 1 provides an overview the ontology network described above

4 4 Vila-Suero, Villazón-Terrazas, and Gómez-Pérez / datos.bne.es: a Library Linked Data Dataset 2.3. Connectivity In order to analyse the internal structure and connectivity the instances the dataset, Table 1 presents the number instances per class, and Table 2 presents the number relationship established. It can be observed that there s is high number Manifestations, Works, Persons, and Expressions, which correspond to the core entities FRBR and in general to the main entities the bibliographic world. Furthermore, among the most established relationships are those that connect these core entities, namely is creator (between a person and a work), is realized through (between a work and an expression), and is embodied in (between an expression and a manifestation). The total number relationships established between instances within the dataset is 9,394,711, while the total number instances is 7,418,635. From these data it can be stated that: (1) althought a high number relationships has been established, this version the dataset only covers primary relationships from FRBR, therefore there is still room for improvement, (2) the dataset provides a high number inverse relationships (e.g. is creator, is created by) which can facilitate traversing the graphs in several directions. Finally, in Section 3 a concrete example the internal structure and connectivity the dataset will be discussed. Regarding the external connectivity (i.e. the number links to external datasets), datos.bne.es linksets can be divided into two groups: (1) equivalence links using the owl:sameas object property, and (2) links to Lexvo dataset 27 using dcterms:language property. As for the equivalence links, datos.bne.es is linked to the following datasets (in descending order): VIAF (454,068), GND 28 (76,413), DBPedia 29 (36,431), Libris 30 (10,884), and SUDOC 31 (9,725). The total number owl:sameas links is 587,521, while the number dcterms:language links is 3,112,900. From the analysis external links, the following can be conclude: (1) there is a high number owl:sameas links to external library datasets, but these links cover only authority entities, namely Persons, Corporate Bodies, Works and Expressions, (2) for a future version the GND is the authority file from the German National Library, see The French University Union Catalogue, see idref.fr/ dataset, links at the level bibliographic entities (i.e. manifestations) should be explored, (3) a high number links to Lexvo languages resources has been established providing rich information about language resources (e.g. different notations language codes, description a certain language in several natural languages). The same approach can be used for enriching the dataset with other resources, for example by linking to geographical descriptions (e.g. geonames) General features To conclude this section, Table 3 provides a summary the main features and statistics, according to the VoID vocabulary[1]. The complete VoID file describing the majority these characteristics can be found at ttl. 3. Miguel de Cervantes Graph Analysis This section is devoted to show a brief example the data that can be found within datos.bne.es dataset. More specifically, it discusses some the characteristics a representative graph, a portion the data related to Miguel de Cervantes Saavedra, which can help to understand and illustrate the dataset internal structure. Additionally, his experiment can help potential consumers to understand the main entities and the relationships between them. In order to perform the experiment, the following SPARQL query has been built: 1 construct{ 2 < XX >?r?y. 3?y?r2?y2. 4?y2?r3?y } where { 7 < XX >?r?y. 8?y?r2?y2. 9?y2?r3?y3. 10 filter(!isliteral(?y) ). filter(! isliteral(?y2) ). FILTER regex(? y, "^ "). FILTER regex(?y2, "^ datos.bne.es/resource") 11. filter(!isliteral(?y3) ). FILTER regex(?y3, "^ resource") 12 }

5 Vila-Suero, Villazón-Terrazas, and Gómez-Pérez / datos.bne.es: a Library Linked Data Dataset 5 Table 2 Object properties and their usage accross the datos.bne.es Label URI Count language 3,112,900 is creator (person) 2,129,222 is created by (person) 2,129,222 is embodiment 1,246,773 is embodied in 1,246,773 is realized through 1,054,736 is realization 1,054,736 same as 587,520 subject 249,560 Fig. 2. Miguel de Cervante s Graph visualization

6 6 Vila-Suero, Villazón-Terrazas, and Gómez-Pérez / datos.bne.es: a Library Linked Data Dataset Table 3 Overview the dataset characteristics Property VoID property Value Homepage foaf:homepage Void file - Datahub page foaf:page Publisher dcterms:publisher License dcterms:license Base URI for instances void:urispace SPARQL Endpoint void:sparqlendpoint Data Dumps address void:datadump Total number triples void:triples 58,053,215 Total number entities void:entities 7,412,286 Total number distinct subjects void:distinctsubjects 7,413,108 Total number distinct objects void:distinctobjects 4,716,874 This query builds a graph around the RDF resource corresponding to Miguel de Cervantes 32. Each node the graph corresponds to one RDF resource, and each edge corresponds to a relationships between two nodes. According to the FRBR ontology, the graph describes the works created by Miguel de Cervantes, the different expressions each work (e.g. the English version Don Quijote de la Mancha), and the different manifestations each expression (e.g. a publication from 1898 the English expression Don Quijote de la Mancha), and more importantly the relationshuos between these resources. Figure 2 depicts the analysed graph (a full size version can be found at es/graphvis/). In the figure, the black dots represent the nodes (3,281 nodes), and the green edges represent the relationships between the nodes (3,974 edges), having each type relationship a different tone green (darker green represents creator relationships, while lighter greens represent is realized through and is embodied in relationships respectively). Cervantes node can be found in the center the graph, surrounded by a high concentration dark green edges, while the highest concentration black nodes corresponds to the most edited versions Cervantes For example, the cluster at the top the graph groups all the different manifestations Don Quijote de la Mancha in its original version (Spanish). 4. Conclusions This paper has provided a description the main characteristics the datos.bne.es dataset. This aims at facilitating the reuse this valuable data from the National Library Spain, as well as to provide an overview the main decisions regarding modelling and the known short-commings, which could help for both future versions this dataset and serve as a reference for other cultural institutions willing to transform their catalogue data into RDF. References [1] K. Alexander, R. Cyganiak, M. Hausenblas, and J. Zhao. Describing linked datasets with the void vocabulary, [2] IFLA. Functional Requirements for Authority Data, [3] IFLA. Functional requirements for bibliographic records : final report [4] IFLA. Functional Requirements for Subject Authority Data, [5] IFLA. ISBD: International Standard Bibliographic Description: Consolidated Edition. IFLA Series on Bibliographic Control. De Gruyter, 2011.