Identifiers

Digital Object Identifier - a digital identifier for any object of intellectual property (from DOI FAQ, mEDRA and The Biology Wiki).

The DOI is a Handle System implementation.

The Handle System is a comprehensive system for assigning, managing, and resolving persistent identifiers, known as "handles," for digital objects and other resources on the Internet.

If you give each object a name (a handle), and associate that name with the object's location using the Handle System, you'd only have to update the handle record with the new location, not notify everyone who might want to find the object.

Proxy servers (DOI resolvers)

• http://hdl.handle.net/
• http://dx.doi.org/
• http://www.crossref.org/05researchers/58doi_resolver.html (goes to http://dx.doi.org/)

• DOI lookup
• OpenURL resolver can be used to retrieve DOI metadata in XML

Description of OpenURL standard OpenURL is a NISO standard syntax for transporting information (metadata and identifiers) about one or multiple resources within URLs. OpenURL provides a syntax for encoding metadata (but not a source of it), restricted to the world of URLs (unlike DOI's wider application).

On Making and Identifying a Copy

To obtain a DOI Prefix, you need to work either with a DOI Registration Agency or, for experimental or prototype purposes, with the International DOI Foundation. To obtain a DOI prefix for experimental use, write to the IDF at contact@doi.org, giving clear indication why it is required. Prefixes issued directly by the IDF will be at a cost of US$1,000 per prefix. These prefixes will be issued purely at the discretion of the IDF. List of agencies.

DOI Numbering

All DOIs start with "10." This distinguishes a DOI from any other implementation of the Handle System.

The DOI consists of a unique alpha-numeric character string divided in two parts: a prefix and a suffix. For example:

• 10.1000/abc

where:

• 10.1000 is the prefix
• 10 identifies the string as a DOI
• 1000 identifies the publisher
• abc is the suffix (identifying the digital object)

The suffix can integrate other standard identifiers such as ISBN or ISSN. As a consequence, the DOI allows to mantain the standard identifiers already in use. The suffix is assigned by the publisher (registrant). The DOI suffix can be any alphanumeric string (any printable characters from the Universal Character Set (UCS-2), of ISO/IEC 10646, which is the character set defined by Unicode v2.0). The DOI is an "opaque string" or "dumb number" - nothing at all can or should be inferred from the number in respect of its use in the DOI System.

Handle syntax imposes two constraints on the prefix -- both slash and dot are "reserved characters".

Publishers use many different schemes which all form DOIs that can then be used together: e.g.:

Publisher A uses PII: S1384107697000225
Publisher B uses SICI: 0361-9230(1997)42:<OaEoSR>2.0.TX;2-B
Publisher C uses "C-numbers": JoesPaper56 

These three schemes are not at all interoperable, but become so in the DOI system as:

DOI:10.2345/S1384107697000225
DOI:10.4567/0361-9230(1997)42:<OaEoSR>2.0.TX;2-B
DOI:10.6789/JoesPaper56 

Each publisher can retain his own scheme and does not need to switch to a new one, though all publishers need to agree on a common metadata set for their DOIs.

DOIs are case insensitive. All DOIs are converted to upper case upon registration.

PURL is not very useful because it's inherently dependent on DNS (from PURL evalution)