Re: [xml-dev] Re: determining ID-ness in XML

[Joe English <jenglish@flightlab.com>]

Henry S. Thompson wrote:
> Michael Fuller writes:
>
> > No; but then I never understood why the use of processing instructions
> > had become infra dig. W3C politics, I hear whispered. Anyone care to share?
>
> 1) They're not scoped, everything else about the language is.
> 2) They're not declared in the grammar (DTD/Schema), so their usage is not
> subject to any declarative/universal quality control: you're back to
> writing ad-hoc code in every application to check they occur where and
> how they're supposed to.


This is an argument against using *ad-hoc* processing instructions,
not PIs in general.  It's a bad idea for an XML _vocabulary_
to make excessive use of PIs, but they're well-suited for
XML _architectures_ that are designed to be used with multiple
vocabularies.

The 'xml-stylesheet' PI is a good example of this: you can
use it to attach a stylesheet to documents of any type,
and the only applications that need to pay attention to it
are stylesheet processors.

The very features that make PIs bad for conveying intrinsic
information makes them good for adding extrinsic information.


--Joe English

  jenglish@flightlab.com