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Re: YAXPAPI (Yet Another XML Parser API)- an XDEV proposal

• From: Tim Bray <tbray@t...>
• To: xml-dev@i...
• Date: Sat, 13 Dec 1997 18:41:10 -0800

At 09:01 PM 13/12/97 -0500, David Megginson wrote:
> > What's the boolean?  I don't think the application author should
> > to have to deal with anything but the name and value of attributes.
>The boolean tells whether the attribute was specified or defaulted.  I
>include this to allow people to do useful XML-to-XML transformations.

No.  Not of interest to people who just want to see elements and
attributes.  The whole point of using an XML processor is that it
takes care of these details for the application programmer.  Leave it 
out for now.  If you want XML-to-XML you need a lot more, go use the 
DOM.

> > >  data(XmlParser, String) 
> > I feel that the 2nd argument should not be a String.  It is a recipe
> > for disastrous inefficiency if the processor has to cook up a 
> > java.lang.String object for every little chunk of text.  
>
>The overhead isn't that bad with Ælfred because I coalesce my data
>into the largest chunks possible before allocating the String.  I
>think that returning a char[] array would be confusing for users

that's a fair point; the correct solution per design principles
is to have a Text class that could give you a String if you
asked it; since many applications will ignore the comment of many
elements, it seems vital not to have an interface that makes
lazy evaluation impossible.  So I think you have to go for either
the char[] trick or another class.

> > Lark has a thing where if any callback returns 'true', the
> > parser drops out of its loop... which is awfully useful and easy
> > I think.  Lark will also re-enter, but this need not be a requirement.
>
>Awfully easy with a DFA-driven parser, but trickier with a
>recursive-descent parser like Ælfred.  

But it seems completely unreasonable, if I call the parser mainline,
not to have a way to get control back.  I guess you could get the
client callback to throw an exception... blecch.  If exceptions
are going to be thrown, it's better to hide all this stuff within
the processor and not make each application do it. -Tim


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