Skip Navigation Links  The Library of Congress >> Standards
IFLA/CDNL Alliance for Bibliographic Standards - Library of Congress
  URI Resource Pages Home >> The 'info' Scheme

URI Resource Pages

The 'info' Scheme


The 'info' URI
LCCN Expressed as an 'info' URI
DOI Expressed as an 'info' URI
SRW and NetRef 'info' URIs
'info' and the OpenURL
'info' URI Links

The 'info' URI

The info URI scheme was developed within the library and publishing communities (specifically, in conjunction with the development of the NISO OpenURL standard; more below) because of the need for URIs as pure identifiers, that is, to identify (not retrieve, dereference, locate, name, or any of those other things that URIs do). The most pressing need was to find a way to use URIs to reference information assets that have identifiers in public namespaces but had no representation within the URI allocation – for example, LCCNs.

LCCN Expressed as an 'info' URI

Consider the LCCN:


It is expressed as the following 'info' URI:


Of course sometimes two (or more) apparently different LCCNs are really the same -- for example " 85000002 " and "85-2 ". In that case all of them are expressed as the same URI, which utilizes the LCCN Normalized Form. Both of these normalize to "85000002", and so the 'info' URI representing them is 'info:lccn/85000002'. Another example: both LCCNs "n78-890351" and "n 78890351 " normalize to "n78890351". Thus the 'info' URI representing them is 'info:lccn/n78890351'.

So, LCCN is considered an 'info' namespace. In fact, all 'info' URIs:

  • begin with 'info:';
  • followed by the namespace identifier, e.g. 'lccn';
  • followed by an identifer from that namespace, e.g. from the lccn namespace.

DOI Expressed as an 'info' URI

Consider the DOI:


It is expressed as the following 'info' URI:


See DOI Syntax | DOI Handbook

Info Namespaces

So in general an 'info' URI:

  • Begins with 'info:'.
  • 'info:' is followed by an "info namespace", e.g. 'lccn' or 'doi'. (see the 'info' Registry.)
  • The namespace is followed by a slash ('/');
  • and the remainder of the string is "namespace specific".

Note that we have described a URI in general as "a character string beginning with a scheme name followed by a colon (':') and the remainder of the uri is scheme specific". For an 'info' URI, the scheme is 'info' and the scheme specific part begins following the first colon. The scheme specific part begins with the namespace name followed by a slash which is followed by the namespace specific part.

The namespace specific part of an 'info' URI may be a simple identifier as in the 'lccn' and 'doi' cases, or it may be further structured (and even use further slashes as delimiters) as in the case for SRW and NetRef 'info' URIs.

SRW and NetRef 'info' URIs

Some protocols, notably SRW and NetRef, define object classes, where the objects are identified by URIs. There are various authorities assigning these URIs and though there is no specific rule prescribing what URI scheme is to be used (the authority that defines a URI decides which scheme) many are 'info:' URIs.

Example of an SRW 'info' URI


This identifies diagnostic #2, "System temporarily unavailable", within the diagnostic list assigned by the authority whose authority string is "1". These authorities are assigned by the SRW maintenance agency, which has assigned "1" to itself.

Thus, the above referenced list is the "standard" list of SRW diagnostics, and other diagnostics can be assigned by other authorities. This provides interoperability and extensibility -- interoperability because everyone implements the "standard" list; extensibility because of the provision for additional lists.

See SRW Info URI Page | NetRef Info URI Page

'info' and the OpenURL

OpenURL is a mechanism for context-sensitive linking, by packaging metadata describing a publication of interest to a user, along with other context information about the user or institution, into a URL (the "OpenURL"). The URL is sent to a link resolver, a system that can interpret OpenURLs taking into account local holdings and access privileges of the user's institution, and display links to resources, including, for example, full text of the publication.

OpenURL defines a registry of identifiers, and an 'info' namespace, info:ofi, is defined to facilitate the operation of the Registry. For example:


is an info URI that might occur within an OpenURL and essentially indicates that the object of interest is a book (more specifically that the metadata to follow is metadata specific to a book). See more at

OpenURL has also defined another 'info' namespace, info:sid, the "Namespace of Source Identifiers used in the OpenURL Framework".

To understand the OpenURL and the role of these identifiers it is useful to look at a typical OpenURL scenario: A journal article in a database cites another journal article. The "citation" takes the form of an OpenURL, that is, it encodes several pieces of information, including:the referring entity (the citing article); the referent (the cited article), and the referrer (the database).

Look at 10.2 of Z39.88-2004: The OpenURL Framework for Context-Sensitive Services, The Key/Encoded-Value (KEV) Format Implementation Guidelines. In this example a user reads an article (the referring entity) in the Elsevier ScienceDirect collection (the referrer) and finds a reference to another article (the referent).

The Referent is described not only by identifiers (two of them), but also by metadata. The identifiers are (1) a DOI, supplied by an info:doi URI; and (2) a Pub Med identifier supplied by an info:pmid URI. The metadata is supplied as genre, author last name, etc., but it is the metadata format that is of interest: it is identified by an info:ofi URI. In this case it serves to indicate that the metadata that follows is metadata defined for journal articles.

&rft.atitle=Isolation of a common receptor for coxsackie B viruses and adenoviruses 2 and 5

And is a similar fashion the referring entity is described:

&rfe.jtitle=Molecular Therapy
&rfe.atitle=p27-p16 Chimera: A Superior Antiproliferative for the Prevention of Neointimal Hyperplasia

And finally, the referrer is described simply via an info:sid URI:


Useful 'info' URI Links

Top of Page Top of Page
  URI Resource Pages Home >> The 'info' Scheme
  The Library of Congress >> Standards
  May 31, 2007
Contact Us