Re: Problem about imported schema type when processing XQuery

The constraint:

 

For a given query, define a participating ISSD as the in-scope schema definitions of a module that is used in evaluating the query. If two participating ISSDs contain a definition for the same schema type, element name, or attribute name, the definitions must be equivalent in both ISSDs."

 

applies to the query as a whole. Each module in the query has its own (participating) ISSD. This rule says that the ISSD for one module must be consistent with the ISSD for every other module; specifically, if two modules import definitions of a particular schema type, then those definitions must be "equivalent" (which isn't precisely defined, but that's another problem).

 

Michael Kay

http://www.saxonica.com/

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From: he harrison [mailto:harrison076@g...]
Sent: 02 January 2008 13:26
To: Michael Kay
Cc: xml-dev@l...
Subject: Re: Problem about imported schema type when processing XQuery module import

Hi, Micheal, thanks for your reply, however I am still in doubt.
According to the definition of "participating ISSD", it's a kind of in-scope schema definitions,
then whether in-scope schema definitions include schemas imported in other imported modules?

There are two statement in spec.:

A module import imports only functions and variable declarations; it does not import other objects from the imported modules, such as in-scope schema definitions or statically known namespaces.

and

It is a static error [err:XQST0036] to import a module if the importing module's in-scope schema types do not include definitions for the schema type names that appear in the declarations of variables and functions (whether in an argument type or return type) that are present in the imported module and are referenced in the importing module.

From upon two statement, we could make the conclusion that in-scope schema definitions should not include schemas imported in other imported modules, otherwise [err:XQST0036] will be unnecessary, therefore "participating ISSD" should also not include schemas imported in other imported modules, right?

So I think two modules import identical type qname with different difinition is not an error,
unless variables with one of the types are passed to another module.

The section 2.2.5's constraints that require the types derived from validating input documents to be consistent with those that are imported into the static context helps me to clarify
another problem, thanks.

2008/1/2, Michael Kay <mike@s... >:

I think the mailing list at talk@x... would be a better place for such a question. As it happens, your question is very similar to one raised this morning on that list by Weihua Jiang of Intel.

 

I believe that your query violates the rule in the penultimate bullet of 2.2.5 in the XQuery specification:

 

"For a given query, define a participating ISSD as the in-scope schema definitions of a module that is used in evaluating the query. If two participating ISSDs contain a definition for the same schema type, element name, or attribute name, the definitions must be equivalent in both ISSDs."

 

The introductory paragraph of 2.2.5 says "This specification does not define the result of a query under any condition in which one or more of these constraints is not satisfied." - in other words, it's an error to have two different types with the same name, but it's not an error that an implementation is required to detect and report. So it's not surprising that you get different results from different processors, nor that the results are "obviously wrong".

 

Section 2.2.5 also imposes constraints that require the types derived from validating input documents to be consistent with those that are imported into the static context.

 

Michael Kay

http://www.saxonica.com/

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From: he harrison [mailto:harrison076@g...]
Sent: 02 January 2008 03:12
To: xml-dev@l...
Subject: Problem about imported schema type when processing XQuery module import

Hi, I come up with a problem when reading XQuery spec., following is my case:

a.xq:

module namespace ma="http://www.w3.org/TestModules/moduleA ";
import schema namespace simple="http://www.w3.org/XQueryTest/simple" at "schema_a.xsd";
declare function ma:funcA()
{
   "40" cast as simple:myType
};

b.xq:

module namespace mb="http://www.w3.org/TestModules/moduleB";
import module namespace ma="http://www.w3.org/TestModules/moduleA" at "a.xq";
declare function mb:funcB()
{
   ma:funcA() treat as xs:integer
};

c.xq:

declare namespace mc="http://www.w3.org/TestModules/moduleC";
import module namespace mb="http://www.w3.org/TestModules/moduleB" at "b.xq";
import schema namespace simple=" http://www.w3.org/XQueryTest/simple " at "schema_c.xsd";

declare function mc:funcC()
{
  mb:funcB() instance of simple:myType
};

<result>{mc:funcC()}</result>

schema_a.xsd:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:simple="http://www.w3.org/XQueryTest/simple"
           targetNamespace="http://www.w3.org/XQueryTest/simple"
           elementFormDefault="qualified" attributeFormDefault="qualified"
>
  <xs:simpleType name = "myType">
     <xs:restriction base = "xs:int">
      <xs:minInclusive value = "1"/>
      <xs:maxInclusive value = "50"/>
    </xs:restriction>
   </xs:simpleType>   
</xs:schema>

schema_c.xsd:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:simple="http://www.w3.org/XQueryTest/simple"
           targetNamespace="http://www.w3.org/XQueryTest/simple"
           elementFormDefault="qualified" attributeFormDefault="qualified"
>
  <xs:simpleType name = "myType">
     <xs:restriction base = "xs:int">
      <xs:minInclusive value = "51"/>
      <xs:maxInclusive value = "100"/>
    </xs:restriction>
   </xs:simpleType>   
</xs:schema>

Main module is c.xq, what should be output?
The key problem is, whether we need to keep different type definition in each module,
in case imported types have same name and actually are different?
I tried some XQuery processors, they all give different result and most of them are obviously wrong...

Another further problem is, if we choose to ignore types imported from other modules, while we need to recognize types bring by XML documents,
then it seems confusion when we handle a returned value of a function, as we need to distinguish where the value comes from:
defined by module or get from document.