This paper presents a hybrid document recommender system intended for use in digital libraries and institutional repositories that are part of the Slovenian Open Access Infrastructure. The recommender system provides recommendations of similar documents across different digital libraries and institutional repositories with the aim to connect researchers and improve collaboration efforts. The hybrid recommender system makes use of document processing techniques, document metadata, and the similarity ranking function BM25 to provide content-based recommendations as a primary method. It also uses collaborative-filtering methods as a secondary method in a cascade hybrid recommendation technique. We also provide a real-world data feedback collection analysis for our hybrid recommender system on an academic digital repository in order to be able to identify suitable time-frames for direct feedback collection during the year.

The paper presents the legal, organisational and technical perspectives regarding the implementation of the Slovenian national open access infrastructure for electronic theses and dissertations as well as for research publications. The infrastructure consists of four institutional repositories and a national portal that aggregates content from the university repositories and other Slovenian archives in order to provide a common search engine, recommendation of similar publications, and similar text detection. We have developed the software which is integrated with the universities' information and authentication systems and with the COBISS.SI. During the project the necessary legal background was defined and processes for mandatory submission of electronic theses and dissertations as well as of research publications were designed. The processes for data exchange between the institutional repositories and the national portal, and the processes for similar text detection and recommendation system were established. Bilingual web and mobile applications, a recommendation system and the interface suitable for persons with disabilities are provided to the users from around the world. The repositories are an effective promotion tool for universities and their researchers. It is expected that they will improve the recognition of Slovenian universities in the world. The complex national open access infrastructure with similar text detection support and integration with other systems will enable the storage of almost eighty percent of peer-reviewed scientific papers, annually published by Slovenian researchers. The majority of electronic theses and dissertations yearly produced at the Slovenian higher education institutions will also be accessible.