LOD Workshop: “Literary corpora unchained” – (almost) live!

From April 23rd to 25th 2018, the CLiGS grouped welcomes two researchers from Spain: Helena Bermúdez Sabel and Pablo Ruiz Fabo from the Universidad Nacional de Educación a Distancia (UNED) in Madrid came to Würzburg to give a workshop on Linked Open Data (LOD) and to present their project POSTDATA (“Poetry Standardization and Linked Open Data”). As part of their visit, they will hold an evening lecture entitled “Linked Open Data: Unchain your Corpora”. The main goals of the workshop, which has been organized by José Calvo Tello, are to exchange experiences in modelling and creating literary corpora in the POSTDATA and CLiGS projects, as well as to discuss possibilities of using LOD approaches to enrich and interlink these data. This is a live report of the ongoing workshop – well, almost live. The blog post will grow with each session of the workshop that we finish.

On the first day of the workshop, Helena and Pablo presented their ongoing work in the POSTDATA project. Helena outlined the aims and scope of the whole project, which rests on three main axes: a Semantic Web infrastructure using LOD, a Virtual Research Environment for the creation of digital editions, and the so-called Poetry Lab designed to support Natural Language Processing (NLP) tasks for the analysis of poetry. Furthermore, Helena reported on her work to design a conceptual model for poetry on the basis of existing collections from different European contexts. A special challenge lies in the mapping of the diverse concepts and the resulting trade-off between an interoperable metadata scheme on the one hand, and a semantically rich one on the other hand. Pablo introduced some approaches to identify metrical structures and enjambements automatically, by means of NLP techniques suited for the Spanish language. A recent tool developed for this purpose is ANJA (Automatic Enjambment Analyzer).

The participants of the CLiGS group contributed short introductions into their work, as well. In particular, the metadata collected for the literary texts in the CLiGS textbox, the publication platform for text collections created in the junior research group, was discussed. The goal was to identify categories that could be enriched with the help of LOD techniques. At the same time, it was considered for which data it would be useful to offer them in a LOD format such as RDF, for example. Besides the textbox corpora, the TEI data of the digital bibliography BibAcMé would be a candidate for LOD. BibAcMé is connected to the corpus of 19th century Spanish American novels and provides bibliographical information about authors, works and editions beyond the core text collection. Both in textbox and BibAcMé, no LOD technologies are used yet. As an example for a text collection which already benefits from Semantic Web technologies, the DISCO corpus was mentioned. In this Diachronic Spanish Sonnet Corpus, poems written from the 15th to the 19th century by canonical and minor authors with a European or American Spanish background are assembled. Pablo Ruiz Fabo, Helena Bermúdez Sabel, and José Calvo Tello are part of the team that curates and develops the DISCO corpus. In DISCO, RDFa attributes are used for biographical metadata to link to VIAF, Wikidata and esDBPedia.


On Tuesday, Helena introduced us to the basic ideas of the Semantic Web and LOD with a  presentation “Introduction to LOD resources”. How can we get from “data” to “wisdom”? For example, by starting to break down information silos and start to build networks of open data. In order to do that, the data needs to be published in a structured way and using semantics, not just strings, so that it can be interlinked and queried automatically and in a meaningful way. A lot of linked open data is already out in the world wide web, as can be seen in the Linked Open Data cloud diagram that Helena showed to us:

The Linked Open Data cloud diagram: http://lod-cloud.net/
The Linked Open Data cloud diagram: http://lod-cloud.net/

The bulk of red dots to the left are LOD from the Life Sciences, to the right a big group of governmental LOD resources can be seen (in yellow), as well as a larger homogeneous network of linguistic resources (green). But where are the LOD from literary studies? Clearly, we have a good reason to be here to learn how to prepare and publish our data about literary texts as LOD! Before learning how to create our own LOD datasets, though, we start by trying to query existing resources. For this purpose, Helena gave a short introduction into the query language SPARQL and let us jump in at the deep end with some exercises:

First experiences with SPARQL in the Cophi (computational philology) meeting room.
Querying a generic SPARQL endpoint.
First results: names of persons mentioned in the edition of “Anathomie”, the first treatise of the Grand Chirurgie written by Gui de Chauliac.

The afternoon session started with another presentation by Helena: “Introduction to RDFa: LOD-ifying a corpus”. We learned that “RDF in Attributes” is an accessible option to start “lodifying” our data: on the basis of this W3C standard, RDF can be directly embedded into HTML, XHTML and other XML standards by means of specific attributes. Like this, websites (or TEI data, as in our case) can be enhanced with machine readable and interoperable semantic information. This standard does provide the syntax and a frame for LOD, but it does not define any specific terms, so external vocabularies have to be used to formulate statements in RDFa. How to know which vocabularies and which terms to use? One possibility is to consult the Linked Open Vocabularies site:

The Linked Open Vocabularies site.
The Linked Open Vocabularies site.

How to open up your dataset? Add RDF links that point to URIs identifying resources in your dataset and ask people to point to URIs of your own dataset, or, in a nutshell: Get in touch. We started with the first step and thought about how we could add RDF links to the TEI files in the CLiGS textbox. This is an example of what we came up with so far:

The TEI Header of the file nh0011.xml from CLiGS textbox, enhanced by RDFa statements.

The following statements are added to the first part of the header of the TEI file:

  • The entity with the VIAF-ID 190446859 is a creative work and is a text.
  • The creator of this creative work is another entity with the VIAF-ID 24681042.
  • The title of the creative work is “Sin rumbo”.
  • Another kind of title of it is “(Estudio)”.
  • Another kind of title of it is “Rumbo”.
  • The entity with the VIAF-ID 24681042 is a person.
  • The name of this person is “Cambaceres, Eugenio”.
  • Another kind of name of this person is “Cambaceres”.
  • Another version of the creative work is the file nh0011.xml in the CLiGS textbox (= this TEI file).
  • This TEI file is itself a creative work and a text.
  • There is an entity with the ORCID-ID 000-0003-2852-065X which is also a person.
  • The name of this person is “Ulrike Henny-Krahmer”.
  • This person is the editor of the TEI file identified by a URI in the CLiGS textbox (= this TEI file).

So there is already a lot of information that can be converted to LOD just in the title statement of the TEI header. To get from the RDFa embedded into a host format to “real” RDF in a serialized format, the online tool RDFa 1.1 Distiller and Parser can be used. It is possible to upload the XML file and decide on an output format, for example RDF/XML or Turtle.

The Turtle version of the RDFa-enhanced TEI title statement.

A nice tool to visualize RDF graphs is the W3C RDF Validation Service. This is the whole graph:

Visualization of the TEI title statement graph of the novel “Sin Rumbo” written by Eugenio Cambaceres.

After this hands-on session, which was a great start into the practical part of the workshop, we decided to call it a day!


On Wednesday, the workshop continued with a presentation by Pablo on “NLP Toolkits: LangTech-ifying a corpus”. But just after we had started, an alarm signal rang out and we had to leave the building. Luckily, the weather was pleasant, so we gathered outside and took the opportunity to take a group picture:

Speakers and participants of the LOD-workshop near the philosophy department at the University of Würzburg.

After this unplanned interruption, Pablo could continue his presentation and we learned about types of linguistic technologies and existing tools that are language-independent or that have been specifically developed or trained for Spanish. In CLiGS, we can use these linguistic technologies to operationalize literary concepts that we want to analyze in the texts, for example Named Entity Recognition (NER) together with coreference resolution, to detect mentions of characters in a prose text.

We looked at generic NLP tasks and pipelines (including, for example, tokenization, part-of-speech-tagging, syntactic parsing, and tagging of semantic roles), as well as special and advanced tasks such as the detection of key phrases, entity linking, word sense disambiguation, and custom phrase-matching (i.e. matching of domain-specific terms and phrases). Frameworks and tools that were recommended by Pablo include the IXA pipes library, FreeLing, SpaCy (sets of NLP tools for several languages), the KafNafParserPy (a python library to parse the formats KAF and NAF that are used to represent output of linguistic tagging). We talked about different possibilities to use NLP tools: in the form of locally installed programs or by calling web services.

In the last part of the workshop, Pablo showed us a live demo of an application that he developed as part of his PhD work: The Climate Negotiation Analysis tool is built on the IXA pipes library and the Python web framework Django. It allows to navigate actors and their statements in the Earth Negotiations Bulletin, a corpus on international climate negotiations.

After that, we had time to test the library SpaCy with a Jupyter notebook that Pablo had prepared for us. It is incredibly easy to start using SpaCy! The library can be imported with a simple import statement. Next, the language package is loaded, in this case Spanish. After that, the library is ready to use. The following picture shows the results for the example sentence “El hombre bajo toca un bajo bajo el baobab”:

Using the NLP library SpaCy with Python in a Jupyter notebook.


After a short break on Wednesday afternoon, Helena and Pablo held their evening lecture on “Linked Open Data: Unchain your Corpora”. Helena compared western literature to a tree with branches grown together and many connections over time. She explained that the project POSTDATA builds on these interconnections when conceiving an overall conceptual model for poetry from all over Europe. Following the thoughts expressed in a white paper written by Jannidis and Flanders (“Knowledge Organization and Data Modeling in the Humanities”), the LOD approach can be considered a form of “altruistic”, “curation-driven modeling”, designed to enable knowledge sharing and reuse instead of fulfilling very specific local research needs. Pablo pointed out that NLP is a helpful means to capture linguistic traces of literary traits. Besides these general considerations about the usefulness of LOD and NLP approaches, they briefly outlined the goals of the POSTDATA project, the DISCO sonnet corpus and the enjambment detection tool Anja. Helena concluded that LOD might help to achieve a bigger picture about literature over time, in different regions and languages, and to overcome the still usual specialization of individual research projects. At the same time, a more accurate picture might emerge.

The talk was well received and followed by some discussion, for example about the question to what extent LOD approaches are advantageous over econding schemas like TEI. The challenges in finding and defining a common conceptual model for European poetry of all kinds, from different countries, linguistic and cultural contexts, from medieval to modern times, were also emphasized. The audience is eagerly awaiting the publication of the resulting conceptual model.

Pablo Ruiz Fabo presenting the DISCO corpus.*

* There was an audience! Just hidden behind the first rows of seats.

Helena Bermudez Sabel reflecting on the limits and possibilities of LOD approaches for literary studies.*
Both speakers held their own in the discussion following their talk.

We thank Helena and Pablo very much for their visit, the interesting, informative and enjoyable workshop, and the evening lecture. All in all, it became clear that there is still much room for literary studies to enter the scene of Linked Open Data. Who knows whether the data produced in the context of the POSTDATA and CLiGS projects could not be linked to each other in the future. We already noticed that poetry, which is at the heart of the POSTDATA project, is the only principal genre not covered in the CLiGS textbox yet. What is certain is that Helena and Pablo have equipped us with the skills we would need to “lodify” and “langtechify” our corpora.

¡¡¡Muchas gracias!!!

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