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Uniform Resource Identifiers
Uniform Resource Locators (URLs) describe the location of a
resource on the Internet and the protocol which is used to access the resource.
An object on WWW may be available in many locations: for example popular
browsers, such as NCSA Mosaic, are available from anonymous FTP servers in many
locations around the world. The mirroring of files helps to minimise network
traffic over busy links, such as the trans-Atlantic link. Mirroring also
reduces the load on the central server. Uniform Resource Names (URNs)
will provide a mechanism for uniquely identifying a resource. In the future it
is likely that a browser will request a URN rather than a URL. A URN to URL
resolver will locate the nearest object (nearest in network terms).
Uniform Resource Characteristics (URCs) will provide meta-information about a document. This information could include information about the author, keywords, expiry dates (for caching servers), copyright and cost information. URCs could also provide information about the quality of the document. For example a seal of approval (SOAP) could be given by university publications group which confirms, by the use of a digital signature, that the document is a PhD thesis.
Uniform Resource Agents (URAs) will provide tools to search for information on the Internet. For further information see the URL http://nic.nordu.net:80/ftp/internet-drafts/draft-ietf-uri-ura-00.txt
Uniform Resource Identifiers (URIs) includes URLs, URIs and URCs. The URI specification is available as RFC 1630. The mailing list uri@bunyip.com is used to discuss URIs. Send email to uri-request@bunyip.com to subscribe to this list. Archives of the list are available at the URL http://www.acl.lanl.gov/URI/archive/uri-archive.index.html
New Facilities
CCI
NCSA Mosaic For X (version 2.5) provides support for CCI (Common Client
Interface). This will provide a standard mechanism by which WWW browsers can
communicate with external programs. A number of demonstrations of this
facility are available, including a slideshow program, which instructs Mosaic
to display URLs which are specified in a file. A program called xwebteach
provides a mechanism by which a teacher can control the display of Mosaic on
student's machines. Further information about the CCI specification is
available at the URL
http://www.ncsa.uiuc.edu/SDG/Software/Mosaic/Docs/cci-spec.html
W3A
W3A (World-Wide Web Applets) is a proposal for a standard API for
dynamically linking applets (which can be defined as a piece of software that
can be attached to a host program such as a WWW browser). Further information
is available at the URL
http://www.let.rug.nl/~bert/W3A/W3A
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Graphics Multimedia Virtual Environments Visualisation Contents