Re: XSLT and XPath 2.0 development

[Udi <ud...@conformative.com>]

regarding this (old) mail, could you please give details of the current
plans (if any) for 2.0 support in Xalan-C ?
thanx,    -udi-

----- Original Message ----- 
From: "Henry Zongaro" <zo...@ca.ibm.com>
To: <xa...@xml.apache.org>
Sent: Thursday, August 28, 2003 4:54 AM
Subject: XSLT and XPath 2.0 development


> Hello,
>
>      Last year, several Xalan-J developers worked on a prototype
> implementation of the XSLT/XPath 2.0 draft recommendations based on the
> Xalan-Java Interpretive processor.  The work was carried out on the xslt20
> branch of the xml-xalan module.  Some preliminary work also began on 2.0
> support for XSLTC.  As the developers who worked on the xslt20 branch
> began to focus on other projects, nobody was available to carry on that
> work, so it has languished for some time.  The work was based on older
> draft revisions of the recommendations; that, coupled with bug fixes and
> performance enhancements on the main branch, has caused the code on the
> xslt20 branch to become badly out of date.
>
>      Over the past year, Xalan-J developers have placed a lot of emphasis
on
> improving XSLTC's level of conformance with the XSLT/XPath 1.0
> recommendations.  More recently, there's been a number of significant
> performance improvements to XSLTC.  The way things currently stand, it
> looks like it would be better for future development of XSLT/XPath 2.0 to
> resume on the XSLTC code-base.  XSLTC has much better performance
> characteristics than Xalan-J Interpretive, and it would be much easier to
> add missing functionality to XSLTC than it would be either to continue
> supporting and developing two very different processors in parallel,
> thereby dividing scarce resources, or to develop only Xalan-J Interpretive
> and try to catch up to XSLTC in terms of performance.
>
>      If there's significant continued interest in Xalan-J Interpretive, or
if
> there are things that could be done with the interpretive processor that
> just can't be done with the compiling processor, we could look at reviving
> XSLT/XPath 2.0 support in Xalan-J Interpretive.  But in the short-term and
> medium-term, I think that we're more likely to see this work succeed by
> focusing on XSLTC.
>
>      Some groundwork for XSLT/XPath 2.0 support in XSLTC has already
> begun.  In particular:
>
> . Morris Kwan has been adapting XSLTC to use the JJTree-generated XPath
> 2.0 parser, using the AST code contributed by Lionel Villard, that was
used on the xslt20 branch - the grammar from which that parser
> is derived is generated from the same source as the grammar that appears
> in the XPath 2.0 draft recommendation.  Scott Boag is bringing the grammar
> up to date with the current version in the latest XPath 2.0 draft.
>
> . Christine Li has begun prototyping support for XPath 2.0 Functions and
> Operators.
>
> . Brian Minchau has begun to look at requirements for serialization in
> XSLT 2.0.
>
> . Joseph Kesselman and Myriam Midy have been working to adapt the Extended
> Data Model (XDM) support from the xslt20 branch to XSLTC.  That's not
> really something that enables XSLT/XPath 2.0 support, but rather opens up
> Xalan-J to accepting input from a wide array of sources.
>
>      Very shortly, we'd like to contribute those first pieces of code to
> Apache, and publish a prelimary development plan to get us on the path to
> XSLT/XPath 2.0 support.  There should be plenty of work for all interested
> parties!
>
>      In the meanwhile, I'd like to propose that we rename the existing
> xslt20 branch to xslt20-interp, and that we create a new xslt20-compiled
> branch on which we can develop XSLTC.  It will probably take a fair amount
> of time before the new development can replace the existing processors, so
> I'd propose that we continue to maintain and develop the existing
> XSLT/XPath 1.0 processors on the MAIN branch of xml-xalan.  At some point
> in the future, the community can decide whether to move the new XSLT 2.0
> processor to the MAIN branch.
>
>      Questions, comments, endorsements and objections would be welcomed!
>
> Thanks,
>
> Henry
> ------------------------------------------------------------------
> Henry Zongaro      Xalan development
> IBM SWS Toronto Lab   T/L 969-6044;  Phone +1 905 413-6044
> mailto:zongaro@ca.ibm.com