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Hierarchical link types

From: Philip Taylor <philip@zaynar.demon.co.uk>
Date: Tue, 21 Aug 2007 02:06:55 +0100
Message-ID: <46CA3AAF.3050605@zaynar.demon.co.uk>
To: HTML WG <public-html@w3.org>

A common structure for sets of pages is:

     Table of contents
         /    \
        /      \
  Section A  Section B
    / | \      / | \
   /  |  \    /  |  \
P1  P2  P3  P4  P5  P6

LaTeX2HTML provides various examples:
http://www.lanl.gov/thermoacoustics/Manual/DelEdoc.html
http://www.cs.cmu.edu/afs/cs/project/jair/pub/volume16/drummond02a-html/drummond02a-html.html
http://docs.python.org/lib/lib.html

When each page has important information (e.g. the 'section' pages have 
an introductory paragraph for that section), a user would like to follow 
"next" links through TOC -> A -> P1 -> P2 -> P3 -> B -> P4 -> P5 -> P6. 
(The "next" buttons in the given examples do that.)

When the 'section' pages don't have any useful information (e.g. they're 
just sublists of the table of contents), a user may like to follow P1 -> 
P2 -> P3 -> P4 -> P5 -> P6 instead.

The current definition for "next" ("the link is leading to the document 
that is the next sibling of the current document") doesn't allow authors 
to handle either of those cases, instead requiring the user to follow 
several "up" and (implicit) "down" links to get from P3 to P4, thus 
preventing the user from concentrating fully on the finer details of 
thermoacoustic simulations. (Since the "down" links are never explicitly 
listed or ordered, there is no way for a UA to automatically determine a 
preorder traversal through the tree.)


Suggested redefinition, to allow more flexibility in describing 
"next"/"previous" paths:

     A hierarchical structure of documents is one where each document 
can have various subdocuments. A subdocument is said to be a child of 
the document it is a subdocument of. The document of which it is a 
subdocument is said to be its parent. A document with no parent forms 
the top of the hierarchy. The structure can include non-overlapping 
linear paths through its document set.

     The index keyword indicates that the document is part of a 
hierarchical structure, and that the link is leading to the document 
that is the top of the hierarchy.

     The up keyword indicates that the document is part of a 
hierarchical structure, and that the link is leading to the document 
that is the parent of the current document.

     The first keyword indicates that the document is part of a linear 
path in a hierarchical structure, and that the link is leading to the 
document that is the first in the path.

     The last keyword indicates that the document is part of a linear 
path in a hierarchical structure, and that the link is leading to the 
document that is the last in the path.

     The next keyword indicates that the document is part of a linear 
path in a hierarchical structure, and that the link is leading to the 
document that is the next in the path.

     The prev keyword indicates that the document is part of a linear 
path in a hierarchical structure, and that the link is leading to the 
document that is the previous in the path.

-- 
Philip Taylor
philip@zaynar.demon.co.uk
Received on Tuesday, 21 August 2007 01:07:05 GMT

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