Re: FO DTD from XSL WD.

Subject: Re: FO DTD from XSL WD.
From: Stephen Deach <sdeach@xxxxxxxxx>
Date: Thu, 05 Aug 1999 13:32:51 -0700
At 12:03 1999-08-05 -0700, you wrote:
>
>
>>> Do I understand right that any inheritable attribute,
>>> may appear within *any* element in FO stream?
>
>
>>FOP treats it that way. Another way would be to only allow inheritable
>>attributes on elements whose allowable decendants can use that attribute.
>
>
>Unfortunately, I'm trying to understand what is the way
>proposed by WD. FOP's behavior may be right, but
>behavior of another rendering engine may be
>"another way" - as a result  if somebody is rendering
>some FO with FOP - it may result in producing invalid
>FO's  ( that would be considered invalid ) by another
>software.

1.) An inherited property may be specified on any node in the FO tree.
    (But an inheritable property is only meaningful on the FOs that
    indicate that they can "use" or "apply" the property. So it is
    only useful to specify it on ancestors to the "using" node.)
2.) Inheritance is by hierarchical order in the FOT.
    (Note that this *precludes* setting a property in the layout-master
    and having it inherited by a member of the fo:flow or
    fo:static-content. Flows and static-content are "assigned" to
    regions, they are not children not the region.)

>
>I hope the purpose of WD (or any other stantard)
>is to *avoid* such problems. Isn't it?
>
>>> If no - is there any way to understand what
>>> attribute is valid for some element? Usualy we are
>>> using ATTLIST to explain such relations, right?
>>
>>Yes. But you are supposing that there is value in a notion of validity that
>>is contraining enough to rule out attributes that won't be used. I don't
>>necessarily disagree with you, but it is worth noting that it is a design
>>decision whenever developing schemata (and I always include DTDs when I say
>>'schemata') which constraints are in the schema and which you check at the
>>application level. Some schema languages can express more than others. For
>>example, a FO DTD couldn't constrain the values of "font-size" to those the
>>prose of XSL WD does. The new W3C XML Schema language will be able to in
>>this particular example.
>
>
>I understand this point, but unfortunately I don't
>see too much relation.  Yes, one should use CDATA
>for any attribute. It's OK. The WD provides
>all the materials you need to validate the
>value of font-size. It seems that  WD provides you
>with no information about what is the relation
>between elements and their attributes and this is
>*very* strange.
>
>>> For some reason XSL WD is not using DTD for
>>> that ordinary and trivial purpose, but is using DTD
>>> syntax for some other purpose.
>>
>>A useful purpose, though. One that is aimed more at implementors than
>>stylesheet writers. Of course, it would be perfectly possible to have a DTD
>>for both, still bearing in mind that there will be a lot of constraints
>>*not* expressed in the DTD.
>
>
>Unfortunately in this case we have a situation when constrains
>are not expressed *at all*, not only in the DTD.

I think this clarifies the issue sufficiently for the WG, so that we can
clean up the spec.


>
>Rgds.Paul.
>
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>
>
>
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