Re: [xml] Initial identity-constraint implementation for XML Schemata

[Kasimier Buchcik <kbuchcik 4commerce de>]

Hi,

Daniel Veillard wrote:
> On Thu, Jan 27, 2005 at 04:28:09PM +0100, Kasimier Buchcik wrote:
>
> > Preparatory work for (2):
> >  - A streamable XPath engine would be perfect for IDCs, but since there
> >    is none yet available the XPath module is used to compile the IDC
> >    XPath expressions.
>
>
>   Bzzz, checkout CVS :-)
>
> You have 4 new APIs in pattern.h:
>
> XMLPUBFUN xmlStreamCtxtPtr XMLCALL
>                         xmlPatternGetStreamCtxt (xmlPatternPtr comp);
> XMLPUBFUN void XMLCALL
>                         xmlFreeStreamCtxt       (xmlStreamCtxtPtr stream);
> XMLPUBFUN int XMLCALL
>                         xmlStreamPush           (xmlStreamCtxtPtr stream,
>                                                  const xmlChar *name,
>                                                  const xmlChar *ns);
> XMLPUBFUN int XMLCALL
>                         xmlStreamPop            (xmlStreamCtxtPtr stream);
>
>  Basically the operation is that you call
>     push(name, ns) on all element start
>     pop() on all element end
> and push() returns 1 if the element matches the pattern.
>
>  I't not yet fully completed, but works for simple cases, I added code
> to test it in xmllint --stream --pattern .
>  Things needing work:
>    - compilation flags to check for specific syntaxes
>      using flags of xmlPatterncompile() 
>    - making clear how pattern starting with / or . need to be handled,
>      currently push(NULL, NULL) means a reset of the streaming context
>      and indicating we are on / (the document node), probably need 
>      something similar for .
>    - xmlPatterncompile support of namespaces arguments, I'm not sure
>      it's implemented and definitely not tested
>    - handling of disjunction "pattern1 | pattern2" mean needed to build
>      and check a list internally
>    - better testing, I'm pretty sure there is some bugs left in the
>      engine :-)
>
> So there is still a bit of work needed :-), APIs should be okay though.
> For the last node() or attribute @foo needed specifically for schemas
> patterns I suggest to handle them on top of the engine, I'm not sure
> we want to add attributes to xmlStreamPush() for example.
>
> The good part is that the XPath subset is so restricted that if can be done
> in a very lightweight way, and I hope to be able to reuse that to speed
> up significantly XPath implementaton for that subset by reusing it.
>
> So quite a bit of work, but a lot of fun ahead,
>
> Daniel
Coool!
I integrated it into the schema module. Works nice for the test schema
I'm using, didn't test special cases yet. Fixed some bugs in the IDC
code. I'll try to commit soon.

Thanks & regards,

Kasimier