[XML-SIG] Re: While we're on the subject of xmlproc, DTDs and validation ...

[Jim Fulton]

Lars Marius Garshol wrote:
> 
> * Jim Fulton
> |
> | I'd like to have a very fast and simple parser that can do
> | validation.
> 
> Hmmm. Maybe a better option than what you've been looking at would be
> RXP, which is an all-C validating parser.
> 
> <URL: http://www.cogsci.ed.ac.uk/~richard/rxp.html>

I'll check it out.  I'm a little bit worried about the license, 
which is GPL. Maybe I can get him to change it to LGPL.

> It's a little bit slower than expat, but that should drown in the time
> occupied by the Python callbacks anyway.

True, although for alot of our projects, we'll probably write 
many (most?) of the callbacks in C.
 
> I've been thinking about writing a Python interface to RXP, but am not
> really into C extensions yet and haven't got the time at the moment.
> 
> |   - Using (or stealing parts of) xmlproc to parse DTDs,
> 
> This is easily possible, and it will buy you some performance,
> although probably not as much as you'd wish. (Especially for large
> DTDs xmlproc is slow.)

In Most cases, I'd expect to amortize DTD parsing over many documents, 
either by preprocessing standard DTDs or catching DTDs.
 
(snip)
 
> | I find that if I tell xmlproc to parse a file containing only a DTD,
> | it will build the DTD related data structures for me, but:
> |
> |   - I wonder if there is or should be a tool designed
> |     just to do this.  Maybe there already is one that I've
> |     missed.
> 
> xmlproc comes with a dtdparser.py module which gives you an
> event-based interface to DTDs. Combined with the classes in xmldtd.py
> this gives you the ability to parse a DTD without an associated
> document.

I suspected this, but I had trouble figuring out the interface.

> Look in the demo directory for dtddoc.py, which is an
> example of this.

Ah, thanks.  That should help alot.
 
> |   - Can I rely on the data structures created by the current
> |     xmlproc?
> 
> Sorry, I don't understand the question. What do you mean by 'rely'?

I'll write something that takes as input the data structures
created internally whan xmlproc parses a document.  If you change 
those data structures, my software will break. :)
 
> | I'd like to have a tool for processing DTDs independent of
> | parsing XML:
> |
> | [excellent reasons snipped]
> 
> Yup. These were all part of my motivation for making the DTD parsing
> module of xmlproc separate from the rest.

Cool.

Jim

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