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From "Andreas Veithen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AXIOM-367) Improving AXIOMXPath to support XPath 2.0
Date Mon, 01 Apr 2013 18:57:15 GMT

    [ https://issues.apache.org/jira/browse/AXIOM-367?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13619052#comment-13619052
] 

Andreas Veithen commented on AXIOM-367:
---------------------------------------

Some thoughts on this:

(1) XPath 2.0 is schema aware. For this to work the XPath processor needs access to the type
information produced by the validating parser. That is what PhysoPath’s TypeModel is about.
However, Axiom doesn’t support type information and it likely never will because (as far
as I know) StAX doesn’t have any API to retrieve that information. That means that XPath
2.0 support in Axiom would always be limited to schema unaware processing.

(2) The fact that PsychoPath is coupled to DOM would reduce its usefulness for Axiom even
more because many projects won’t benefit from it. E.g. it could not be used by Apache Synapse
because that project only supports LLOM.

(3) Because of (1) the work required to integrate PsychoPath with Axiom would be to ensure
that DOOM has a level of compliance to DOM that is high enough to support PsychoPath. That
would make building a GSoC project on that idea somewhat risky because it is difficult to
estimate the required effort. It could be that only some minor improvements are required,
but it could also be that one encounters some unexpected issues (e.g. PsychoPath depending
on some Xerces specific behavior) that would make this hard to achieve. One really has no
a priori idea whether the required effort is appropriate for a GSoC project or not.

(4) Saxon-HE may still be a good candidate. Saxon-EE adds schema aware processing, but because
of (1) that is likely out of scope anyway. The primary question is whether Saxon-HE supports
integration with object models other than DOM or if that feature is only available in Saxon-PE/EE.

(5) As described in (2), Synapse doesn’t support DOOM. There used to be some fundamental
limitations that justified this. One was that the OMFactory implementations for DOOM had a
different lifecycle, but this was fixed by AXIOM-412. The other is that DOOM doesn’t support
OMSourcedElement, but adding that support should not be too hard, and this is actually envisaged
by AXIOM-447. Maybe working on DOOM support for Synapse could be an interesting project for
GSoC.
                
> Improving AXIOMXPath to support XPath 2.0 
> ------------------------------------------
>
>                 Key: AXIOM-367
>                 URL: https://issues.apache.org/jira/browse/AXIOM-367
>             Project: Axiom
>          Issue Type: Improvement
>            Reporter: Heshan Suriyaarachchi
>              Labels: gsoc2013
>             Fix For: 1.2.16
>
>
> AXIOMXPath is developed by extending org.jaxen.BaseXPath. Since Jaxen is only supporting
Xpath 1.0, Axiom XPath will also be only supporting XPath 1.0. It would be really useful if
AXIOMXPath is improved to support XPath 2.0. It will be beneficial for the projects which
are using AXIOMXPath. eg. Apache Synapse is also extending AXIOMXPath in it's org.apache.synapse.util.xpath.SynapseXPath
implementation. 

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