Michael, I'm using Xerces-J 2.9.1, I even upgraded from 2.9.0 today to
test any changes!
Jeff, can you bear with me here I think I understand you...
Jeff Greif wrote:
Maybe an example will be clearer.
The instance document is, relative to some subtree of the file system, in
instances/articles/doc1.xml
There is a set of schemas that apply in
schemas/{a,b,c,d}.xsd
Suppose a.xsd imports b.xsd, and in addition, doc1.xml refers to
components from nsa, the namespace of a, and nsb, the namespace of b.
So there are schema locations of the form {nsa, ../../schemas/a.xsd
nsb ../../schemas/b.xsd, ... }
Now when the reference from doc1 -> nsb is found, the schema locations
can be used to find b.xsd.
I'm with you up to here, because the schema locations were defined in
doc1.xml they are relative to doc1.xml and therefore point to the
correct xsd files.
> If the reference from a.xsd -> nsb is
found, the schema locations will not work, because the location is
incorrect relative to the location of a.xsd.
My reference from a.xsd -> nsb is in the form
<xsd:import namepsace="nsb" schemaLocation="./b.xsd" />
This path to b.xsd is correct with respect to the a.xsd it is defined in
(although incorrect with respect to doc1.xml).
However this schema location hint is second in the queue behind the one
specified in doc1.xml, when Xerces tries to use the one specified in
doc1.xml here it fails with File Not Found(because when relative to
a.xsd the doc1.xml's schema location is not valid), reports the error
and stops parsing so the schema location specified here is never used.
Other parsers continue looking at the hints in schema location and find
the correct one specified on the <xsd:import> line, is there any way of
telling Xerces to try all hints matching that namespace (in the same way
XMLSpy, Microsoft .NET's System.Xml and Saxonica seem to do) rather than
stop on the first "not found"?
> You couldn't solve the
problem by changing the schema locations to look like {nsa,
../../schemas/a.xsd nsb ./b.xsd, ... } because the doc1 -> nsb
reference would fail. However, in the first case, if the parser is
caching grammars, and the reference from doc1 -> nsb has already been
processed, the a.xsd -> nsb reference might not be a validation error
-- the schema locations are only a hint to the parser, and if it has
located and parsed the right grammar already, it can use it.
So changing the schemaLocation works in my case because in processing
a.xsd the parser finds b.xsd (via the schemaLocation relative to a.xsd)
and caches it, therefore meaning it can use the cached copy in doc1.xml.
These are the problems with using relative URLs for the schema
locations, except in certain special cases. For example, if the
instance doc is
instances/doc1.xml
and the schemas are in
schemas/{a,b,c,...}.xsd
Then these schema locations: {nsa ../schemas/a.xsd nsb
../schemas/b.xsd ...} will work successfully, but only because the
paths work whether the reference is from the instance doc or a schema
doc.
Ideally I'd like to specify a "try all schema locations before error" or
"do not stop on file not found error" property since there will *always*
be one that works when used relative to the current location, is there a
way of doing this?
I'm guessing there is no "schema locations per file" property to turn
off the global cache of schema location and switch to a per-file cache?
Thus forcing Xerces to use the hint found at the current location.
Maybe the easiest way to solve my problem is to re-jig my document
locations so that the same relative path can be used to locate each of
the schemas? Not ideal mind since I've spent a long time developing the
inter-schema links to ensure they can always be linked together and I'd
like to use that investment in some way and I can't help but think that
moving the files so the relative paths fit for both scenarios is more of
a by-product than something implemented by design.
I'm under some commercial pressure here to switch to the method that
works with the system that the customers use (XMLSpy et al) but I'd
really like the same examples to work in Xerces-J, we've been extolling
the virtues of XML and XMLSchema as the "common language" to unify our
industry's data exchange and it'd look bad to have to change the
examples we are producing to make them work in different parsers!
Once again, that ended up a lot longer than I expected and I hope it
makes sense, thanks for your time and patience.
Chris
Jeff
On 10/8/07, Chris Bray <[EMAIL PROTECTED]> wrote:
Jeff.
My comments inline.
Chris
Jeff Greif wrote:
When a relative URL is used for the location of an imported schema, it
is supposed to be relative to the URL of the importing document. So
if your instance document directly references the namespaces of one or
more schemas for validation, whose URLs are interpreted relative to
the location of the instance document. Probably some of the schemas
So my instance document _should_ have relative paths to the individual
schemas in it's schemaLocation?
Does the fact that Xerces is "changing" the base path to that of the
first specified schema for each subsequent schema constitute a bug?
Should I log this somewhere more formal?
contain <xsd:import> elements; those would require URLs relative to
the schema importing them.
Each of those schemas then further includes others using <xsd:import>
and <xsd:include> (for example core.xsd actually includes about 30 or 40
smaller schemas from ./Core/schemaname.xsd) and this works as I'd
expected it to.
Some of the schemas might be referenced both in the instance document
and in imports from other schemas referenced in the instance document.
I'm not sure there's a specification of where they must be found if
relative URLs are used. This may depend on the ordering of processing
of those references by the parser/validator.
When that is the case I am 100% sure that both the instance document and
the "sub schemas" refer to the exact same document, so it shouldn't
matter which of the references Xerces is using, it will resolve to the
same schema anyway.
There is a section in the XML Schema 1.0 spec addressing this issue.
Jeff
On 10/8/07, Chris Bray <[EMAIL PROTECTED]> wrote:
Parshant,
Changing the working dir of the JVM doesn't seem to make any difference,
using dom.Counter from the Xerces-J samples the parser still seems to
change the working dir first to wherever the xml file is located, then
to wherever the first xsd file specified is located and need all
subsequent locations to be relative to that.
Absolute paths work fine but I'm trying to include these files bundled
in with a set of schema as examples of how to use the format, hence I
don't know where my users will unzip the archives to (C:\Users\username,
c:\projects\projectname\, /usr/local/projects, /home etc) so I can't set
absolute paths in my distributed files.
I was hoping to not need to actually write my own parsing program, just
use the output from dom.Counter and a schemaLocation hint (which fits my
needs perfectly) since I'm not really a Java developer.
I saw that jEdit page but I'd rather make my schemas validate against a
standard Xerces installation than modify my jEdit installation to make
them work, I feel this would be more useful for my users.
Chris
Prashant Reddy wrote:
I think the relative paths you have specified in the schemaLocation will
be resolved against the "working dir". The working dir is usually the
directory at the cmd prompt when you launched the JVM.
Have you tried giving absolute path to the XSD files ?
A more portable solution to finding schema files locally is to use
EntityResolver[1].
If you are using JAXP 1.3/ JDK 1.5+ see :
https://jaxp.dev.java.net/article/jaxp-1_3-article.html
[1]:http://java.sun.com/j2se/1.5.0/docs/api/org/xml/sax/EntityResolver.html
Hope this helps.
-Prashant
On Mon, 2007-10-08 at 13:17 +0100, Chris Bray wrote:
All.
Please go easy on me as I'm a newbie here, if this is a really obvious
problem I'm really sorry!
I've been using Xerces to validate XML for a while now, and I've found a
troublesome scenario.
In the top of my xml files I have a line specifying the location of the
external schemas required for this xml file like so:
xsi:schemaLocation="http://www.diggsml.org/0.9.2
../Schemas/diggs/core.xsd http://www.diggsml.org/0.9.2/geotechnical
../Schemas/diggs/geotechnical.xsd "
In this case specifying two namespaces and their associated schema files
(files exist and paths are correct).
However this doesn't work using Xerces. I am required to change my
schemaLocation attribute so that the first path points to its xsd, then
subsequent entries are relative to that first xsd, not to the current
file, like so:
xsi:schemaLocation=" http://www.diggsml.org/0.9.2
../Schemas/diggs/core.xsd http://www.diggsml.org/0.9.2/geotechnical
../geotechnical.xsd "
Is there any way I can change this to work like the first example, as
other parsers (XMLSpy and Stylus Studio in particular) require the first
syntax, all paths relative to current doc, what I believe to be correct
behaviour. I don't know how to build Xerces-J from source to fix(?) this
myself but I'd be willing to try if anyone can help me get it building.
Since my customers are all using XMLSpy etc I'm having to produce my
example files in the earlier syntax, stopping my from using Xerces to
validate them.
As the biggest advocate of Free/OpenSource software in our group (jEdit
with Xerces plugin in particular) I really don't want to have to change
to use XMLSpy or Stylus Studio but this is quite awkward for me!
That ended up being a longer mail than I'd expected! I hope you can
help, if there's any more information you need (or a small set of sample
files) let me know.
Chris Bray
Software Engineer (DIGGS Project)
Keynetix Ltd.
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