Re: [docbook] XLink and OLink in Docbook 5

[Jirka Kosek <jirka@kosek.cz>]

Peter Ring wrote:

> We're considering up-translating some legacy content with lots of
> external links and cross-references to Docbook. We've been using
> olink for maintaining external links, so I'd like to get an idea
> about what to expect from Docbook V5.0. Can I re-implement the
> existing targetdoc#targetptr semantics of olink with xlink?

Yes, you can. There is an easy mapping from DocBook 4.x linking into 
DocBook 5 linking:

1) link, xref

<link linend="foo">...</link> (same for xref)

can be written as:

<link linend="foo">...</link>
or
<link xlink:href="#foo">...</link>

2) ulink

<ulink url="foo">...</link>

will be

<link xlink:href="foo">...</link>

3) olink

This mapping is not so straightforward as targetdoc in olink is not URI 
but rather identifier pointing into olink database. So one possibility 
is to use real URI of referenced document instead of symbolic name:

<link xlink:href="target_doc_URI#targetptr">...</link>

instead of

<olink targetdoc="target_doc" targetptr="targetptr">...</olink>

AFAIK stylesheet doesn't yet support this, but you can be almost sure 
that support for such olinks will be added in a future.

Moreover xlink:href and linkend are presented on almost any element, so 
you can do things like:

<para><application 
xlink:href="http://www.gnu.org/software/emacs/emacs.html";>Emacs</application> 
is the best editor.</para>

<para>Function <function linkend="strstr.reference">strstr</function> 
can be used for substring searching.</para>

> We seriously want to use extended links, i.e., external linkbases. In
> 2001, XLink looked like a promissing technology, but since then, most
> of the XLink processors have disappeared. Anyone out there using
> extended XLinks today?

I hear silence :-)

But there will be the extendedlink, arc and locator elements in DocBook 
5. Is this sufficient for your needs? If not, could you please describe 
your needs in a more detailed way and provide some use case.

				Jirka

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