Here are the general principles:
1. The schema processor must be able to obtain the location of all schemas
it must use to validate the instance document and the schemas used to
validate that document (if this level of validation is desired.)
2. **While reading a schema** it can use that schema's imports to find
schemas on which the first schemas depend, and so on recursively.
3. It must be able to find the schema for the namespace of the root
element of an instance document, either from a schema location in the
instance document or from some other external means (the
externalSchemaLocations property of the Xerces parser, or an entity
resolver, for instance).
4 Having found the schema for the root element, typically any others
needed will be found via import or include elements or schema location
settings in the document or parser configuration.
In your case, schema1 imported schema2, schema2 contained the definition of
the root element of the document, and you specified schema1's location in
the document. Since schema1's namespace was irrelevant to the validation of
the root element, there was no reason for xerces to look inside it to see if
it indicated where to find schema2.
The short answer is that the processor needs to be able to find the schema
for the root element of the document. If you have several kinds of
documents, with root elements in different schemas, you need to be able
specify the correct schema location for each one. If the schema for the
root element depends on others, they must be specified in imports, and the
locations specified somehow (import or otherwise). If any schema allows
wildcards or anyType, or element substitutions, or derived datatypes from
other namespaces, the locations of the schemas for those namespaces actually
referenced in the instance document must be available to the
parser/validator.
Jeff
Jeff
----- Original Message -----
From: "Adachi Seiichi" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, August 26, 2003 5:15 AM
Subject: Re: Schema validation using multiple schemas
> Bob, Jeff,
>
> Thank you for your replies.
>
> I have 2 questions.
>
> 1. I understand that there may be a need to specify schema#2 in the
> xsi:SchemaLocation of the XML file. However, for a more complex XML
> schema, wouldn't this mean that you would have to specify all the
> schemas in each XML file?
>
> Yes, this problem can be resolved if you specify the location of schema#2
> in
> the XML file. However, the XML schemas for my application will be more
> complex and I do not want to specify all the schemas that are involved.
>
> I am not that familiar with XML but it was my understanding that when
> creating an XML file, you do not need to specify the location of all the
> schema files that are declared as namespaces inside the XML file, if
> they are defined (imported) by the schemas that are specified in the
> xsi:schemaLocation of the XML file. At least, that is what it said in
> the 2 XML Schema books I have here. (Sorry, they are in Japanese)
> I guess this maybe wrong. To confirm the specification on
> <xsi:schemaLocation> and <xsd:import> when using multiple namespaces, I
> have been looking at the w3c documents and searching the web, but have
> not found a clear answer on this topic. Is this specified somewhere?
>
> 2. This relates to question#1, but Xerces-J 2.5.0 is able to
> resolve the location of imported schema if it is not the root element.
> For example :
>
> test2.xml
> ---------
> <book xmlns='http://foo.com/namespace3'
> xmlns:ns4='http://foo.com/namespace4'
> xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'
> xsi:schemaLocation='http://foo.com/namespace3 ns3.xsd'>
> <ns4:chapter>sample XML file</ns4:chapter>
> </book>
>
> ns3.xsd
> -------
> <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
> targetNamespace="http://foo.com/namespace3"
> xmlns="http://foo.com/namespace3"
> xmlns:ns4="http://foo.com/namespace4"
> elementFormDefault="qualified">
>
> <xsd:import namespace="http://foo.com/namespace4"
> schemaLocation="ns4.xsd" />
>
> <xsd:element name="book">
> <xsd:complexType>
> <xsd:sequence>
> <xsd:element ref="ns4:chapter"/>
> </xsd:sequence>
> </xsd:complexType>
> </xsd:element>
>
> </xsd:schema>
>
> ns4.xsd
> -------
> <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
> targetNamespace="http://foo.com/namespace4"
> xmlns="http://foo.com/namespace4"
> elementFormDefault="qualified">
>
> <xsd:element name="chapter" type="xsd:string"/>
>
> </xsd:schema>
>
> Since this file is validated correctly, I had assumed Xerces-J 2.5.0
> supports these kind of files. Is there any possibility that unable to
> resolve it in the case of the root element is a bug? (I know they are
> implemented differently but just as a note, Xerces-C 2.3.0 did not
> return any errors.) Or is this strictly an implementation dependent
matter?
>
> Thanks,
>
> Seiichi
>
>
>
> >From: "Jeff Greif" <[EMAIL PROTECTED]>
> >Reply-To: [EMAIL PROTECTED]
> >To: <[EMAIL PROTECTED]>
> >Subject: Re: Schema validation using multiple schemas
> >Date: Mon, 25 Aug 2003 06:51:45 -0700
> >
> >Probably xerces proceeds like this:
> >
> >Xerces must be able to directly locate the schema for the namespace of
the
> >root element. It does not read schema#1 (for a seemingly irrelevant
> >namespace) in the hopes of finding the location of schema#2. If schema
> #1
> >is in the schemaLocation attribute of the instance document, it should
> work.
> >You can include both schemas there if you choose.
> >
> >This is not redundant with the import element in schema#1. That import
is
> >required in order to make it legal to refer in schema#1 to items from
> >schema#2.
> >
> >Jeff
> >
> >
> >----- Original Message -----
> >From: "Adachi Seiichi" <[EMAIL PROTECTED]>
> >To: <[EMAIL PROTECTED]>
> >Sent: Monday, August 25, 2003 1:39 AM
> >Subject: Schema validation using multiple schemas
> >
> >
> > > Hi All,
> > >
> > > I am trying to validate an xml file using multiple schema files using
> > > Xerces-J 2.5.0. The xml file specifies the location of schema#1 using
> > > schemaLocation. Inside of schema#1, schema#2 is specified using
> > > xsd:import. I get an error when the root element of the xml file is
an
> > > element defined in schema#2.
> > >
> >
> >
> >---------------------------------------------------------------------
> >To unsubscribe, e-mail: [EMAIL PROTECTED]
> >For additional commands, e-mail: [EMAIL PROTECTED]
> >
>
> _________________________________________________________________
> 自宅の PC で英語力をアップ MSN 英会話
> http://englishtown.msn.co.jp/
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: [EMAIL PROTECTED]
> For additional commands, e-mail: [EMAIL PROTECTED]
>
>
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
