Re: [Vtd-xml-users] xerces discussion on VTD

[Tatu S. <cow...@ya...>]

--- Jimmy Zhang <cra...@co...> wrote:

> A few things about this default element/attribute
> val feature in schema at
> the moment
> 
> 1. This feature is not really about validation

Right. It is one of ill-defined features of W3C Schema
(IMO), and was probably added to make it easier to
transition from DTDs, as DTD allows attribute
defaulting. Thank god Schema didn't port over general
entities, though.

There's a term to describe result of Schema validated
document, with possible augmentations (PSVI,
Post-Schema-Validation Infoset?).

> 2.  it seems more like a way to modify the XML
> structure.
> 
> do you see this as an essential feature of XSD?

Although I can't answer for Boris, I assume it all
depends on use cases. For some use cases and users it
may, for others not.
But more than this, whether those use cases are core
use cases for VTD.

I have said this before, but I think there is value in
knowing exactly where and to whom VTD could add most
value. Whether it eventually gets used for wide-range
of tasks or not, there are some areas where it seems
more optimal than others. And from that one could ask
the question: "does Schema in general matter for [core
use cases]; and if it does, is attribute defaulting
used for them".

>From my perspective, VTD's main potential benefit is
its speed. But for many Schema-dependant use cases,
users do not care (or are ignorant).
I have seen enough developers write code where they
convert from Strings to JDOM trees and back, happily
using convenience methods to construct dynamic xpath
expression all over the place, that I honestly do not
think most developers care. Even by just properly
using existing tools they'd get significant
improvements.
For them, it all comes down to perceived simplicity of
API. Usually they are pretty happy when they see, say,
XOM, after using DOM for a while.

And then there are other use cases where performance
does matter, and people are willing to invest time in
understanding new tools and learning new APIs. That's
where solutions like VTD may come in handy.

-+ Tatu +-



 
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