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Re: from-page-master-region() and Re: reference-orientation

From: Peter B. West <lists@pbw.id.au>
Date: Tue, 09 Aug 2005 15:22:31 +0100
Message-ID: <42F8BC27.9040700@pbw.id.au>
To: xsl-editors <xsl-editors@w3.org>

Peter B. West wrote:
> Sharon,
> My apologies for taking so long to respond.
> I did appreciate that the use of the function did not violate lexical
> (is that an appropriate term?) inheritance.  My concern was with the
> mooted changes to "6.4.5 fo:page-sequence", under "Trait Derivation".
>  'The reference-orientation and writing-mode of the
>  region-viewport-areas are determined by the values of the
>  "reference-orientation" and "writing-mode" properties of the
>  fo:page-sequence.'
> Is this change still in play?


The answer, as the Last Call makes clear, is "yes".  What a astonishing
performance by the editors.

This change purports to be a "clarification."  What it clarifies is that
in 1.0 (and the initial draft of 1.1), reference-orientation and
writing-mode defined on elements of fo:simple-page-master subtrees were
completely inaccessible.  In neither 1.0 or the first draft of 1.1 do
reference-orientation or writing-mode appear as properties applying to
fo:page-sequence.  They do, however, appear as properties applying to
fo:simple-page-master, fo:region-body, fo:region-before,
fo:region-after, fo:region-start and fo:region-end.  They still do.

A basic prop of the Recommendation has been the inheritance of
properties down the FO tree: not, as far as I have ever been able to
tell, down the "FO tree that holds the content."  For instance, see my
substantially unanswered in
which refers me to http://www.w3.org/2001/08/28-XSL-PR-DOC , comment 20,
item 3, a response to a message of 10 Jan 2001, which states, "The
design approach taken for XSL was to have a simple inheritance model.
Making this change would obviously introduce an exception to this model. ...
The consensus of the working group was to not introduce this breaking of
the inheritance as it is sometimes very useful and in the cases where it
is not what the stylesheet author wishes it is very easy to make an
explicit specification ..."

That, of course, is also the case here.  Should an author be unable, for
reasons which escape me, to construct sufficient fo:simple-page-masters
to cover their requirements, and insist on overriding the
reference-orientation and writing-mode on the fo:simple-page-master they
just specified for the current fo:page-sequence, there is always the
option to create a top-level reference-area to contain the contents of
fo:flow and fo:static-content.

The simple-page-master subtree has all the tools for specifying
orientation and mode on every region, and that is the job of the page

However, the editors have chosen discard the simple inheritance
principle, but only in the fo:layout-master-set subtree, and only with
respect to reference-orientation and writing-mode.

My suggestion is to remove most of this "clarification" from the draft,
along with from-page-master-region (still defined, incidentally, with an
optional argument which it is an error to use, and other infelicities),
and to replace that function with the following:
object from-page-sequence()
The from-page-page-sequence function returns the computed value of the
property for which the expression is being evaluated.

In XSL 1.1 this function may only be used as the value of the
"writing-mode" and "reference-orientation" properties.

The computed value of the designated property is taken from
fo:page-sequence ancestor of the formatting object on which the function
is being applied.  It is an error if the formatting object has no
fo:page-sequence ancestor.

fo:page-sequence will still need its new adornments of "7.21.3
reference-orientation" and "7.29.7 writing-mode" among the set of
properties applying.

Thanks for your attention.

> Sharon Adler wrote:
>>Yes you are correct in that we should not violate our rule to have
>>inheritance down the  FO tree that holds the content.  We do not believe we
>>have properties that inherit from the fo:layout-master-set.  Pulling a
>>value using a property-value function is not inheritance.
>>Thanks again for your comments and interest in XSL 1.1.
>>Sharon Adler wrote:
>>>I must apologize for taking so long to answer your comment on XSL 1.1.
>>>value your comments and recognize that we need to introduce an
>>>mechanism that inherits selectively from the layout rather than down
>>>formatting object tree.  However, we believe that this is part of a more
>>>extensive set of functionality we wish to introduce in the next version
>>>XSL.  It is at that time that we will design "layout-driven inheritance".
>>>Thank you for your interest in XSL 1.1.
>>Thank you for your response.  I have some feeling for the difficulties
>>the editors face with these questions.
>>Given that the editors wish to retain a simple FO tree inheritance
>>model, it seems to me important that such a principle not be violated
>>for the properties on the fo:layout-master-set subtree.  If properties
>>on, e.g., individual fo:region-body elements are inherited, not down the
>>fo:layout-master-set subtree, but through the fo:page-sequence-master,
>>then FO tree inheritance has been partially replaced by layout driven
>>I much appreciate the efforts of the editors.

Peter B. West <http://cv.pbw.id.au/>
Folio <http://defoe.sourceforge.net/folio/>
<http://folio.bkbits.net/> <- the atTridged version
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Received on Tuesday, 9 August 2005 14:22:51 UTC

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