The Digital Object Identifier (DOI) is a system for identifying content objects in the digital environment. DOIs are names assigned to any entity for use on digital networks. They are used to provide current information, including where they (or information about them) can be found on the Internet. Information about a digital object may change over time, including where to find it, but its DOI will not change. The DOI system provides a framework for persistent identification, managing intellectual content, managing metadata, linking customers with content suppliers, facilitating electronic commerce, and enabling automated management of media. DOIs can be used for any form of management of any data, whether commercial or non-commercial. The system is managed by the International DOI Foundation, an open membership consortium including both commercial and non-commercial partners, and has recently been accepted for standardisation within ISO. Several million DOIs have been assigned by DOI Registration Agencies in the US, Australasia, and Europe. A DOI can be used to identify any resource involved in an intellectual property transaction. Intellectual property includes both physical and digital manifestations, performances and abstract works. An entity can be identified at any arbitrary level of granularity. DOIs can be used to identify, for example, text, audio, images, software, etc; and in future could be used to identify the agreements and parties involved.

The ULAN is a structured vocabulary currently containing around 259,000 names and other information about artists. Names in ULAN may include given names, pseudonyms, variant spellings, names in multiple languages, and names that have changed over time (e.g., married names). Among these names, one is flagged as the preferred name. The focus of each ULAN record is an artist. Currently there are around 118,000 artists in the ULAN. In the database, each artist record (also called a subject in this manual) is identified by a unique numeric ID. Linked to each artist record are names, related artists, sources for the data, and notes. The temporal coverage of the ULAN ranges from Antiquity to the present and the scope is global.

LEAF (Linking and Exploring Authority Files) is a three year project that started in March 2001. It is co-funded within the Information Society Technologies Programme of the Fifth Framework of the European Commission. LEAF develops a model architecture for establishing links between distributed authority records and providing access to them. The system allows uploads of the distributed authorities to the central system and automatically links those authorities concerning the same entity. Information which is retrieved as a result of a query will be stored in a pan-European "Central Name Authority File". This file will grow with each query and at the same time will reflect what data records are relevant to the LEAF users. Libraries and archives wanting to improve authority information will thus be able to prioritise their editing work. Registered users will be able to post annotations to particular data records in the LEAF system, to search for annotations, and to download records in various formats.

The TGN is a structured vocabulary currently containing around 1,102,000 names and other information about places. Names for a place may include names in the vernacular language, English, other languages, historical names, names and in natural order and inverted order. Among these names, one is flagged as the preferred name. The focus of each TGN record is a place. There are around 911,000 places in the TGN. In the database, each place record (also called a subject in this manual) is identified by a unique numeric ID. Linked to the record for the place are names, the place's parent or position in the hierarchy, other relationships, geographic coordinates, notes, sources for the data, and place types, which are terms describing the role of the place (e.g., inhabited place and state capital). The temporal coverage of the TGN ranges from prehistory to the present and the scope is global.