Naming.html
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<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta name="generator" content=
"HTML Tidy for Mac OS X (vers 31 October 2006 - Apple Inc. build 13), see www.w3.org" />
<title>
Naming -- /DesignIssues
</title>
<nextid n="z2" />
</head>
<body bgcolor="#FFC060" text="#302005">
<a href="OldDocs.html"><img src=
"../Icons/WWW/arch1990" /></a>TimBL
<hr />
<h1>
Document Naming
</h1>This is probably the most crucial aspect of design and
standardization in an open hypertext system. It concerns the
syntax of a name by which a document or part of a document (an
anchor) is referenced from anywhere else in the world.
<p>
As many protocols are currently used for information
retrieval, the address must be capable of encompassing many
protocols, access methods or, indeed, naming schemes.
</p>
<p>
The <a name="1" href="../Addressing/Addressing.html">WWW
scheme</a> uses a prefix to give the addressing sub-scheme,
and then a syntax dependent on the prefix used, in order to
be open to any new naming systems.
</p>
<h2>
Name or Address, or Identifier?
</h2>Conventionally, a "name" has tended to mean a logical way
of referring to an object in some abstract name space, while
the term "address" has been used for something which specifies
the physical location. The term "unique identifier" generally
referred to a name which was guaranteed to be unique but had
little significance as regards the logical name or physical
address. A name server was used to convert names or unique
identifiers into addresses.
<p>
With wide-area distributed systems, this distinction blurs.
Locally, things which at first look like physical addresses
develop more and more levels of translation, so that they
cease to give the actual location of the object. At the same
time, a logical name or a unique identifier must contain some
information which allows the name server to know where to
start looking. In a global context, for example
"1237159242346244234232342342423468762342368" might well be
unique, but it contains insufficient (apparent) structure for
a name server to look it up. The name "info.cern.ch" has a
structure which allows a search to be made in several stages.
In fact, practical systems using unique identifiers generally
hide within them some clues for the name server, such as a
node name.
</p>
<p>
A hypertext link to a document ought to be specified using
the most logical name as opposed to a physical address. This
is (almost) the only way of getting over the problem of
documents being physically moved. As the naming scheme
becomes more abstract, resolving the name becomes less of a
simple look-up and more of a search.
</p>
<p>
One expects in practice the translation of a document name
taking several stages as the name becomes less abstract and
more physical.
</p>
<h2>
Hints
</h2>Some document reference formats contain "hints" to the
reader about the document, such as server availability,
copyright status, last known physical address and data formats.
It is very important not to confuse these with the document's
name, as they have a shorter lifetime than the document.
<h2>
X500
</h2>The X500 directory service protocol defines an abstract
name space which is hierarchical. It allows objects such as
organizations, people, and documents to be arranged in a tree.
Whereas the hierarchical structure might make it difficult to
decide in which of two locations to put an object (it's not
hypertext), this does allow a unique name to be given for
anything in the tree. X500 functionally seems to meet the needs
of the logical name space in a wide-area hypertext system.
Implementations are somewhat rare at the moment of writing, so
it cannot be assumed as a general infrastructure.
<p>
If this direction is chosen for naming, it still leaves open
the question of the format of the address into which a
document name will be translated. This must also be left as
open-ended as the set of protocols.
</p>
<address>
<a name="0" href=
"http://www.w3.org./hypertext/TBL_Disclaimer.html">Tim BL
1991</a>
</address>
</body>
</html>