OAI-PMH
The Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH) is a protocol developed by the Open Archives Initiative as a communication infrastructure for Open Access. It is used to collect metadata from documents in an archive so that services can be built using metadata from multiple archives.
IIIF
IIIF (International Image Interoperability Framework) is an open standard for the viewing, analysis, and manipulation of digital images. The main purpose of IIIF is to enable the sharing and interoperability of digital images across different platforms and applications, regardless of the original image format or the system used to store it.
Dublin core
Dublin Core is an international metadata standard, formally known as the Dublin Core Metadata Element Set, and includes 15 metadata terms. These terms offer expanded cataloging information and improved document indexing for search engine programs.
METS schema
Metadata Encoding and Transmission Standard (METS). The METS schema is a standard for encoding descriptive, administrative, and structural metadata regarding objects within a digital library, using the XML schema language, which expresses the hierarchical structure of digital library objects.