The OAI principle

OAI (Open Archive Initiative) is an open, international movement that aims to facilitate the efficient dissemination of content.
The essence of OAI is separating protocol, data- and service provider functions from each other. Data providers (archives) take care of digital content, documents, and they create and maintain the standardised information describing content, the meta-data. According to the OAI principle, the content remains in the possession of the data provider, while the data describing the content must be made available to service providers. Thus service providers collect meta-data only, but not content. The system this way maintains maximum respect for the independence of institutions. The protocol host is the third party, the standard developer organisation co-ordinating the rules for digitisation and transmission of meta-data (and later content).

NDDA, as an organisation of independent archives picked the OAI-PMH protocol to be the basis of data integration among participants. The OAI-PMH protocol is built on the Dublin Core meta-data description standard. The Dublin Core Metadata Initiative is the oldest and most renowned effort set on developing a standard for descriptive data of documents, resources and services available in digital formats, thus making inquiries and recovery easier (The official Hungarian translation of the standard is available here in PDF format.)

OAI technology is inexpensive, easy to implement and suited for connecting systems of diverse architectures. The function of the data provider OAI server system is securing uniform access to data from different databases and satisfying inquiries coming from the internet. The system consists of two distinct groups of components: the server processing inquiries from the internet and the converter-uploader applications that upload the data. The server provides data to the internet from fix format databases. The OAI server implements the OAI-PMH v2.0 protocol, as a result providing data stored in the database (XML in qualified Dublin Core format, a.k.a. QDC) for the queries coming via the internet. Results too are formed in compliance with the OAI-PMH v2.0 protocol.