De Rerum Natura Online
De Rerum Natura Online (DRN) is a flexible framework for creating digital exhibitions. In particular, this demo hosts the heterogeneous collection contained in Vedere l'Invisibile, an exhibition held in Bologna in 2017, regarding the reception of Lucretius' De rerum natura in contemporary art. Starting from heterogeneous data sources (i.e., items of a collection and textual documents regarding De rerum natura and its translations), the application implements modern technological solutions in order to deliver a system that can be both flexible in terms of requirements, reusable and ephemeral. In particular, Omeka S and TEI Publisher have been employed as sources respectively for items and documents. Angular, a single-page framework application, has been used for building the business logic and presentation layer required for parsing the data and representing them homogeneously. Furthermore, RDF(S), Open Annotation and CIDOC CRM have been employed in the creation of a data model for describing multi-layered, narrative paths designed by the curator. This project was generated with Angular CLI version 11.0.2.
Serialization
Items stored in Omeka S are retrieved from an exposed REST API and consequently serialized in JSON-LD, a lightweight Linked Data format based on the largely diffused JSON. A JSON document does not assign any semantics to the keys used. In order to prevent this issue, JSON-LD was introduced as a solution to explicit semantics of keys by adding a so-called context object to documents that describes how the keys are to be interpreted. Technically, this is achieved by adding a new property to a JSON document named @context that describes the semantics by mapping each key to a URI or a datatype.
In the aforementioned API, resources (such as items, item sets and media) have stored their metadata as “resource values”.
Every value has an associated data type that governs how the value is rendered to and ingested from JSON-LD. Moreover, resource values are represented as “top-level” arrays of objects, where each object represents a single value:
Output values are then grouped by property. Object properties common to all data types include:
● type: a string that declares the data type of the value (e.g., literal, uri, resource:media etc.).
● property_id: an integer ID automatically assigned by Omeka S to the object.
● is_public: a boolean that defines if the object is private or public.
● property_label: a string that contains the human-readable name of the related property.
Based on the type value, more properties are allowed. Literal value properties include:
● @value: a string that contains the text of the value.
● @language: a string that contains the language of the text specified in BCP 4749 codes.
URI value properties represent links to external resources and include:
● @id: a string that contains the URI to which the item is linked.
● o:label: a string that contains the human-readable label for the link.
Finally, resource value properties represent links to internal resources and can define an item, an item set or a media.
Data model
As stated before, one of the main goals of this digital exhibition is to create sophisticated museal paths (i.e., stories) based on semantic relationships between textual fragments and items of the collections, and deliver them to the final users. In order to do so, further technologies have been implemented to design and manage semantic relationships.
First of all, it is not always possible to embed metadata or annotations into documents as in the case of the literary works that compose this digital exhibition. In these scenarios, standoff formalisms support the separation between the document and its annotations. The Web Annotation Data Model has been developed by the Open Annotation W3C Community Group and provides a RDF-based approach for standoff annotation of web documents, serialized in JSON-LD. While Web Annotation has been designed to be used across different formats, the most common scenario is to connect text fragments to a single web resource. Web Annotation Data Model has been extended to cover a large number of use cases for structured objects. A typical annotation consists of a Body (i.e., the value of the annotation) that describes information about a Target (i.e., the annotated element), thus forming a directed graph.
TEI Publisher
TEI Publisher facilitates the integration of the TEI Processing Model into exist-db applications. The TEI Processing Model (PM) extends the TEI ODD specification format with a processing model for documents. That way intended processing for all elements can be expressed within the TEI vocabulary itself. It aims at the XML-savvy editor who is familiar with TEI but is not necessarily a developer.
TEI Publisher supports a range of different output media without requiring advanced coding skills. Customising the appearance of the text is all done in TEI by mapping each TEI element to a limited set of well-defined behaviour functions, e.g. “paragraph”, “heading”, “note”, “alternate”, etc. The TEI Processing Model includes a standard mapping, which can be extended by overwriting selected elements. Rendition styles are transparently translated into the different output media types like HTML, XSL-FO, LaTeX, or ePUB. Compared to traditional approaches with XSLT or XQuery, TEI Publisher may thus easily save a few thousand lines of code for media specific stylesheets.
Installation of TEI Publisher
A prebuilt version of the app can be installed from exist-db's central app repository. On your exist-db installation, open the package manager in the dashboard and select "TEI Publisher" for installation. This should automatically install dependencies such as the "TEI Publisher: Processing Model Libraries."
Important: TEI Publisher from version 5.0.0 requires eXist-db 5.0.0 or later.
Development server
Run ng serve for a dev server. Navigate to http://localhost:4200/. The app will automatically reload if you change any of the source files.
Code scaffolding
Run ng generate component component-name to generate a new component. You can also use ng generate directive|pipe|service|class|guard|interface|enum|module.
Build
Run ng build to build the project. The build artifacts will be stored in the dist/ directory. Use the --prod flag for a production build.
Running unit tests
Run ng test to execute the unit tests via Karma.
Running end-to-end tests
Run ng e2e to execute the end-to-end tests via Protractor.
Further help
To get more help on the Angular CLI use ng help or go check out the Angular CLI Overview and Command Reference page.