# The data model in Dissemin¶

This section explains how metadata is represented in Dissemin. There are two important models: OaiRecord and Paper (both defined in papers/models.py).

The OaiRecord model represents an occurence of a paper in some external repository (from the publisher or from an open repository). Each OaiRecord has at least a splash_url (the URL of the landing page of the paper in the repository) and sometimes a pdf_url. The pdf_url is present if and only if we think that the full text is available from this repository. This pdf_url should ideally be a direct link to the full text, but often it is actually equal to the splash_url (but its presence still indicates that the full text is available somehow).

These records are grouped into Paper objects (via a foreign key from OaiRecord to Paper). This deduplication process is done by two criteria:

• first, OaiRecords with the same DOI are merged into the same paper.
• second, we compute a fingerprint of the OaiRecord metadata, which consists of the title, author last names and publication year. Any two OaiRecords with identical fingerprints are also merged into the same Paper.

Dissemin harvests four metadata sources: ORCID, Crossref, BASE and Unpaywall (oadoi). Each of these implements the PaperSource interface, which provides mechanisms to push the papers to the database. The responsibility of each PaperSource is to provide BarePaper instances, which are Python objects representing papers which have not been saved to the database yet (and therefore not deduplicated). When doing this, each PaperSource determines from the medatada they have access to whether pdf_url should be filled or not (depending on whether we think the metadata indicates full text availability).