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Re: [xsl] How to avoid adding defaulted attributes


Subject: Re: [xsl] How to avoid adding defaulted attributes
From: Ihe Onwuka <ihe.onwuka@xxxxxxxxx>
Date: Sun, 12 Jan 2014 06:34:32 +0000

Thanks Wendell, there are different routes to the arrival destination
and how you get there sometimes matters alot. Very attuned to the way
I think.

On Fri, Jan 10, 2014 at 3:03 PM, Wendell Piez <wapiez@xxxxxxxxxxxxxxx> wrote:
> Ihe,
>
> No, that's just pipelining, or "internal pipelining", if you want to
> distinguish it from a pipeline of calls to the XSLT engine as in
> XProc, Ant or a bash/bat script.
>
> Micropipelining is when you use this technique at the level of a
> branch, not of the entire tree.
>
> Admittedly, the distinction is a bit blurry in some architectures.
>
> David writes:
>> yes but looking at the schema doesn't help, if the schema/dtd defaults
>> shape="rect" on every a element (as the HTML4 one does) and you don't
>> want those but do want the 1 in a million times where someone has
>> shape="rect" in their source, then you can't just remove all attributes
>> that are defaulted by the schema, you have to stop the schema defaulting
>> attributes.
>
> Indeed. Yet this raises an interesting conundrum. In the case where we
> need to make a distinction between an attribute value present by
> default and attribute value given in the instance, even when they are
> nominally the same, then evidently (tautologically) they have
> different semantics -- a difference that is blotted out by the
> defaulting mechanism (hence the problem).
>
> (Note I mean "semantics" not in the sense of "what will happen" but in
> the sense of "what might potentially happen", i.e. addressing the
> entire field of what might potentially happen "correctly".)
>
> It is troubling if documents that have been validated to schemas with
> attribute defaults thus have different semantics from identical
> documents that happen not to have been validated. "Valid" is no longer
> just an abstract state that can be tested and confirmed by a process
> called "validation"; now we also have "has been validated" (and thus
> transformed in some way), an internal state in a processing
> architecture.
>
> I think the only clean solutions to this are (a) don't use a schema,
> but instead a normative processing step (XSLT!), to provide attribute
> defaults, or (b) enforce at a policy level the rule that no semantic
> distinction can or should be made between an attribute value provided
> by default, and the same attribute value given in the instance.
>
> Fortunately, except in bad designs (which arguably includes the HTML4
> assignment of shape='rect' to 'a' elements by default), this is mainly
> an edge case. Mostly the problem arises in cases like Mark's, where
> dropping the defaults is only done to optimize the serialization,
> since a subsequent validation step is expected to supply them back
> again anyway.
>
> Yet again, at a deeper level the same problem comes with using schemas
> for type annotation. This is much harder. Type annotation is certainly
> a reasonable requirement -- no argument there. But isn't type
> assignment actually a transformation also? It may be useful to make a
> distinction between a schema used as a specification of lexical and
> syntactic constraints on a set of instances (XML as a string of
> tags-and-tags, not XML as XDM), and a schema used as a specification
> of how to parse an XML document into an XDM for processing.
>
> Cheers, Wendell
> Wendell Piez | http://www.wendellpiez.com
> XML | XSLT | electronic publishing
> Eat Your Vegetables
> _____oo_________o_o___ooooo____ooooooo_^
>
>
> On Fri, Jan 10, 2014 at 3:21 AM, Ihe Onwuka <ihe.onwuka@xxxxxxxxx> wrote:
>> Capture the main output in a variable and apply a template rule to it
>> that gets rid of the attributes you want removed.
>>
>> I think they call this micro pipelining.
>>
>> On Fri, Jan 10, 2014 at 12:53 AM, Mark Giffin <m1879@xxxxxxxxxxxxx> wrote:
>>> I am running an identity transform on some files and changing a few things
as they pass through. They are DITA XML files and their DTDs have defaulted
attributes that do not appear in the instance files. But during the transform
the defaulted attributes are added in on elements that I do not explicitly
handle with XSLT templates. I can stop this behavior by commenting out the
doctypes, but is there a way to do this with some setting? I'm using Saxon PE
9.4.0.6.
>>>
>>> Thanks,
>>> Mark


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