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106 lines
3.8 KiB
106 lines
3.8 KiB
<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta name="generator" content=
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"HTML Tidy for Mac OS X (vers 31 October 2006 - Apple Inc. build 13), see www.w3.org" />
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<title>
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When to use XLink - Design Issues
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</title>
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<link rel="Stylesheet" href="di.css" type="text/css" />
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<meta http-equiv="Content-Type" content=
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"text/html; charset=us-ascii" />
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</head>
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<body bgcolor="#DDFFDD" text="#000000" lang="en" xml:lang="en">
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<address>
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Tim Berners-Lee<br />
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Created Date: 2002/06, last change: $Date: 2002/07/01
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18:33:45 $ Z<br />
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Status: personal view only. Editing status: first draft.
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</address>
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<p>
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Written in response to TAG discussion and specifically
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<a href="http://www.w3.org/2001/tag/ilist#xlinkScope-23">tag
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issue 23</a>
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</p>
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<p>
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<a href="./">Up to Design Issues</a>
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</p>
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<hr />
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<h1>
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When should I use XLink?
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</h1>
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<p>
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When we are designing a new XML language, and we refer to
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something on the web by URI, should we use <a href=
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"">XLink</a>?
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</p>
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<p>
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Three possible answers:
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</p>
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<ol>
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<li>No, you don't have to unless there is some functionality
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of xlink which you would like to lever.
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</li>
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<li>You should use xlink whenever your application is one of
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hypertext linking, as xlink functionality such as power to
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control user interface behavior on link traversal is useful
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and should be implemented in a standard way to allow
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interoperability.
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</li>
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<li>You should always make an XLink whenever you make a
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reference with a URI, as all such references are in some way
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a link.
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</li>
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</ol>
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<p>
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The short answer in my humble opinion, is that (2) is right.
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</p>
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<p>
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When an application uses functionality which is within the
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scope of Xlink, it should use xlink. To do otherwise breaks
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the principle that we are trying to make an interoperable
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web.
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</p>
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<p>
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The third extreme case, that xlink should always be used, is
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not tenable, as URIs are used generally as identifiers for
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everything. Paul Cotton and David Orchard pointed out on a
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TAG call (2002/6/17) that the scope of Xlink is hypertext
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linking. A motivation for XLink was to give to languages for
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human documents a much richer form of hypertext than HTML,
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with features which had in fact been used in hypertext
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products for many years before the web.
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</p>
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<p>
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A counter-example is the speech grammar specification, which
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uses a URI parameter to refer to a piece of grammar in an
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external file. This logical information is not intended to be
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browsed by people as a document. There is no need for the
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hypertext functionality of Xlink. There is no need to clutter
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the language with xlink:href syntax.
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</p>
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<p>
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The idea that all uses of URIs are formally hypertext links
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does not use the term <em>hypertext</em> in the sense I use
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here, or in the sense in which hypertext link functionality
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is the scope of Xlink.
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</p>
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<p>
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The XHTML specification does not use xlink, as (I understand)
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the working group felt that it was too clumsy to use a
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different namespace, and they wanted it to look like HTML,
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which uses href=. The group is (2002/06) looking at schema
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annotation ways of declaring html:href to carry the
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significance of an xlink. These are known as "hlink". The
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pros and cons of schema annotation in general as a means to
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add semantics or style to a langauge are currently under
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debate in the community.
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</p>
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<hr />
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<p>
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<a href="Overview.html">Up to Design Issues</a>
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</p>
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<p>
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<a href="../People/Berners-Lee">Tim BL</a>
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</p>
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</body>
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</html>
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