3:13 a.m.
There have been three responses on wtp-dev about my xml schema
question. They seem to indicate the problem is with the xml spec in
general and the different behaviors in various libraries like xerces.
Either way, this thread seems to indicate Jesper and Keith Chong are the
guys to ping when we have further questions.
- Rob
-------- Forwarded Message --------
Subject: Re: [wtp-dev] Question on XML Validation and oracle xsds
Date: Thu, 25 Feb 2016 23:43:07 +0100
From: Jesper Steen Møller <jesper(a)selskabet.org>
Reply-To: General discussion of project-wide or architectural issues.
<wtp-dev(a)eclipse.org>
To: General discussion of project-wide or architectural issues.
<wtp-dev(a)eclipse.org>
Hi Keith and Rob
(You probably know all this already, but Iâll just add what I know)
I touched some of the validator code a few years back: The number of URI
resolver interfaces is horrible - one from Platform, one from Xerces and
one from WTP as I recall), each introducing a slight impedance mismatch.
Really, the XML Schema spec is at fault, by being so vague on the
semantics of namespaces and schema locations, so Xerces can get away
with their import policies (first import per namespace wins). So, the
order of imports matter, and this affects the effective scope of each
import:
Imagine this scenario where you have to âend-userâ schemas A.xsd and
B.xsd. A relies on namespace C and D, B only on C.
A.xsd imports A_C.xsd, which in turn also imports A_D.xsd (say, they
were meant to be used together), and all is great, you can validate
A.xsd by itself â no errors.
B.xsd import a different file B_C.xsd, which doesnât contain an import
for namespace D, but and doesnât need to. B.xsd also validates by itself.
Now we make E.xsd which import A.xsd and B.xsd and uses namespaces
A,B,C, and D. This should be just fine, and E.xsd can validate on its
own. The import of B_C.xsd from B.xsd is ignored.
Now flip the imports of A.xsd and B.xsd. This will cause the namespace
for C to be imported from B_C.xsd, and E.xsd will no longer validate,
since it never sees the import of A_D.xsd from A_C.xsd. Wonderful,
isnât it?
Now, some short-sighted people even practice splitting namespace
contents up into separate files, for greater âcomposabilityâ, but
the major stacks donât support that.
In Eclipse, the XML Catalog support was supposed to be able to alleviate
this, by allowing the end users manage the schemas themselves (Iâd
rather not have my IDE be dependent on some external server, even if we
cache the result). Also, there is an extension point available for
providing schemas (based on namespace OR schema location IIRC) along
with plug-ins.
We might be able to improve the error handling and logging side of
things, but only by tying deeper into the Xerces code.
-Jesper
On 25. feb. 2016, at 19.01, Keith Chong <kchong(a)ca.ibm.com
<mailto:kchong@ca.ibm.com>> wrote:
Hi Rob
The XML Schema validator is based on the Xerces validator (parser), so
I had a discussion with one of the developers. I'll try to answer your
questions:
1) The validator resolves components via imports so if the import is
missing, the schema is invalid. See:
https://www.w3.org/TR/xmlschema-1/#src-resolve
2) This is a good question. I suspect that this client schema on its
own is 'invalid' and is never intended to be used that way. (There are
no global elements too so you can't create an instance document from
it). The EE 5 schema includes this schema, so it is valid as part of
'the whole'. eg. If you remove the include directive from the EE5
schema, then the EE5 schema is invalid.
3,4,5) are somewhat related. I'm looking into this.
Regards,
Keith Chong
WTP Web Services
<graycol.gif>Rob Stryker ---02/16/2016 12:58:33 PM---Hi All: So after
running into validation issues for our users' xml files using
From: Rob Stryker <rob.stryker(a)redhat.com <mailto:rob.stryker@redhat.com>>
To: "General discussion of project-wide or architectural issues."
<wtp-dev(a)eclipse.org <mailto:wtp-dev@eclipse.org>>
Date: 02/16/2016 12:58 PM
Subject: [wtp-dev] Question on XML Validation and oracle xsds
Sent by: wtp-dev-bounces(a)eclipse.org <mailto:wtp-dev-bounces@eclipse.org>
------------------------------------------------------------------------
Hi All:
So after running into validation issues for our users' xml files using
our schema for week after week, I finally decided to dig in a little and
see how the JEE distribution handles validation of schema without so
many upstream dependencies. It's clear that if a parent or referenced
schema is invalid, the user will experience obscure validation errors
when developing their own webapps etc.
With that in mind I opened
https://bugs.eclipse.org/bugs/show_bug.cgi?id=487851
The usecase is that I simply took oracle's
javaee_web_services_client_1_2.xsd from
http://www.oracle.com/webfolder/technetwork/jsc/xml/ns/javaee/javaee_web_...
and tried to put it in a dynamic web project and let the validator work
its magic.
I wouldn't be posting here if it succeeded ;)
The questions are basically:
1) Why are oracle's xsd's failing to validate? Are they really all
invalid?
2) Why has nobody in the world asked Oracle to fix them?
3) How do we/you, as consumers / extenders of wtp, prevent errors in
oracle's (or other upstream) xsd's from cascading down to our respective
jee / appserver-specific schema when our schema import, extend, or
reference upstream failing xsds?
4) Is this an error in source-editing plugins for not mapping
directly to the most commonly used jee namespaces? Would that even fix
the issue? (It didn't when I tried it but maybe I was doing it wrong).
5) If oracle won't fix their incomplete xsd's, is it reasonable for
source-editing to do it, to make sure each and every one validate
correctly, and that, by extension, all other schema that reference,
import, or otherwise make use of oracles' schema won't be hit by a
series of cascading validation errors?
I suppose it's possible our product is simply "doing it wrong", but the
fact that simply placing an official javaee oracle xsd into a clean JEE
Mars eclipse environment fails validation is indicative to me that
something bigger is going on here.
- Rob Stryker
JBoss Tools And Other Cool Stuff
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