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URI Resource Pages

About URIs: Basic definitions and concepts; URI schemes; what URIs actually do; relationships among URIs, URLs, and URNs.

'info' Scheme: More detailed description about this specific scheme, which is important within the library and publishing communities.

URI Syntax:  A summary of the URI generic syntax.

Latest News: We will try to track the latest URI developments.



URI Background


A URI -- Uniform Resource Identifier -- is a character string that serves to identify (or locate, retrieve, dereference) a resource. Its definition is discussed further in About URIs



URI syntax is discussed in URI Generic Syntax .


A URI is distinguished by its scheme; for example, for the URI the scheme is 'http'. URI schemes are discussed further in About URIs, but basically:

  • A URI begins with a scheme name,
  • the scheme name is followed by a colon (':'),
  • and the remainder of the uri is "scheme specific" -- its interpretation depends on the scheme.

The "Important" Schemes

Two important URI schemes (for libraries) are:
  • 'http', the single most fundamentally important uri scheme for the web; and
  • 'info', a URI scheme of growing importance to the library and publishing community.

There are other important schemes, but (for now) we will focus on these two -- 'info' in particular, as 'http' is almost universally well-understood and we needn't describe it further. The 'info' scheme is discussed in detail in 'info' Scheme.

These pages are maintained at the Library of Congress by the Network Development and MARC Standards Office, as part of its participation in the IFLA CDNL Alliance for Bibliographic Standards (ICABS), to provide information relevant to the library community about URIs, identifiers, locators, and related concepts. Comments, corrections, and suggestions are welcome; please email

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  The Library of Congress >> Standards
  October 28, 2008
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