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