Anno4j - Idiomatic access to the W3C web annotation data model

Abstract

The Web Annotation Data Model proposes standardised RDF structures to form “Web Annotations”. These annotations are used to express metadata information about digital resources and are designed to be shared, linked, tracked back, as well as searched and discovered across different peers. Although this is an expressive and rich way to create metadata, there exists a barrier for non-RDF and SPARQL experts to create and query such information. We propose Anno4j, a Java-based library, as a solution to this problem. The library supports an Object-RDF mapping that enables users to generate Web Annotations by creating plain old Java objects - concepts they are familiar with - while a path-based querying mechanism allows comprehensive information querying. Anno4j follows natural object-oriented idioms including inheritance, polymorphism, and composition to facilitate the development. While supporting the functionality of the Web Annotation Data Model, the library is implemented in a modular way, enabling developers to add enhancements and use case specific model alterations. Features like plugin functionality, transactions, and input/output methods further decrease the boundary for non-RDF experts.