Two of the latter take the form doi:10.xxxx/, which refers to the digital object identifier (DOI) system. As a detailed review indicates, this is by far the most successful application of handles so far: in the middle of 2003, over 10 million DOIs had been assigned. The DOI system has a number of notable additions to the basic handle approach, including an infrastructure that is designed to ensure persistence, and semantic interoperability – the use of a consistent metadata scheme to add information about what the DOI handles refer to.

The kind of metadata that is included reflects the origins of DOI in the publishing world. As the introduction to the DOI system explains, it was designed “for persistent identification and interoperable exchange of intellectual property on digital networks”. In other words, one of its aims is to make digital rights management easier by assigning unchanging identifiers.

A page of sample DOIs includes a paper from the leading scientific journal Nature, and several items from the UK’s largest publisher by output, The Stationery Office (TSO). TSO has set up a site where organisations can create DOIs for their information. It has produced a useful report on various applications of the system, and recently announced that it is supplying thousands of DOIs to the Organisation for Economic Co-operation and Development (OECD). DOIs and handles are clearly beginning to catch on, and with them the idea of replacing ephemeral URLs with perdurable URNs.

Glyn Moody welcomes your comments.