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Re: MPEG-7 Problem Issues and Queries

From: Yoshiaki SHIBATA <yshibata@sslab.sony.co.jp>
Date: Wed, 03 Jan 2001 01:51:36 +0900
To: Jane Hunter <jane@dstc.edu.au>, www-xml-schema-comments@w3.org
Cc: mpeg7-ddl@darmstadt.gmd.de
Message-Id: <E14DVM9-0000CP-00@sslpob>
Dear Jane, all:

Thank you very much for providing a list of queries on XML Schema
where most of our queries are taken into account.
Could you also please add the following question if you don't mind?

-----------
- When we just want to "rename" the existing type, which construct
  <extension>, <restriction> is to be used?

   Example:

  <complexType name="Mpeg7Type">
    <complexContent>
      <restriction base="anyType"/>
    </complexContent>
  </complexType>

   <complexType name="DType">
    <complexContent>
      <restriction base="mpeg7:Mpeg7Type"/>    <!-- <== can we use
"restriction"
         just because its semantics i.e., DType is a special case of
Mpeg7Type? -->
    </complexContent>
  </complexType>
-------------

Actually an advice was given for this question in the reflector. But I also
would
like to hear from the original designer in W3C.

Thank you in advance and best regards

Yoshi

At 21:19 01/01/01 +1000, Jane Hunter wrote:
> Below is a list of queries raised by the MPEG-7 community whilst developing 
> MPEG-7 schemas. On a lot of the issues we're fairly sure of the answer
already 
> but would be highly appreciative of definite clarification.
> 
> regards (and best wishes for 2001),
> 
> Jane Hunter
> -----------------------------------------------
> 1. Global attributes
> 
> When referring to a global attribute whilst declaring a local attribute, 
> can you modify its "use" attribute value and expect this to overwrite the 
> original value?
> 
> Ex:
> 
> <attribute name="myAtt" type="integer"/>
> 
> <complexType>
>    <!-- can we expect the default value, 0, is specified
>         in the following local attribute? -->
>     <attribute ref="myAtt" use="default" value="0"/>
> </complexType>
> 
> 
> --------------------------------------------------------------------
> 2. Root Elements
> 
> Is there a way to specify the root element amongst global elements in an
> instance document ?
> 
> -------------------------------------------------------------------
> 3. Union and IDREF
> 
> Each IDREF must match a corresponding ID within the XML instance document
in 
> which it occurs. Can we expect that this rule also applies when IDREF is
used 
> within a <union>? According to XML Schema definition, it seems not:
> 
>   [Definition:]  Union datatypes are those whose *value spaces* and
>   *lexical spaces* are the union of the value spaces and lexical 
>   spaces of two or more other datatypes. 
> 
> Ex:
> <simpleType name="referenceType">
>   <union memberTypes="IDREF uriReference mpeg7:xPathType"/>
> </simpleType>
> 
> ------------------------------------------------------------------
> 4. Union and attributes
> 
> In Sec 2.5.1.3 of XML Schema Part 2, an example is given as:
> 
>   <xsd:element name='size'>
>     <xsd:simpleType>
>       <xsd:union>
>         <xsd:simpleType>
>           <xsd:restriction base='integer'/>
>         </xsd:simpleType>
>         <xsd:simpleType>
>           <xsd:restriction base='string'/>
>         </xsd:simpleType>
>       </xsd:union>
>     </xsd:simpleType>
>   </xsd:element>
> 
> A possible instance is:
> 
>   <size>1</size>
>   <size>large</size>
>   <size xsi:type='xsd:string'>1</size>
> 
> What happens in the last instance when "size" is also declared as an
> attribute? There seems no way to specify the type using xsi:type 
> when the size is also an attribute.
> 
> ------------------------
> 5. Is it possible to both extend and restrict a locally defined 
>    datatype simultaneously?
> 
> Ex:
> 
> <element name="LinearMatrix">
>   <complexType>
>     <simpleContent>
>       <restriction base="mpeg7:IntegerMatrixType">
>         <minInclusive value="0"/>
>         <maxInclusive value="65535"/>
>       </restriction>
> 
>       <attribute name="sizes" use="fixed" value="3 3"/>
>         <!-- IMPOSSIBLE both extension and restriction -->
> 
>     </simpleContent>
>   </complexType>
> </element>
> 
> ------------------------------------------------------
> 
> 6. Is there any way to constrain the length of a locally defined 
>    list?
> 
> Ex:
> 
> <element name="ColorValueIndex">
>   <simpleType>
>     <list itemType="mpeg7:unsigned12"/>
>         <!-- <length value="3"/> POSSIBLE ?? -->
>   </simpleType>
> </element>
> 
> <simpleType>
>    <list itemType="mpeg7:unsigned8"/>
>        <!-- <minLength value="32"/> IMPOSSIBLE -->
>        <!-- <maxLength value="256"/> IMPOSSIBLE -->
>    <!-- </list> -->
> </simpleType>
> 
> ______________________________________________________
> 
> 7. When deriving a complexType by restriction on a complexType which 
> was itself derived by extension, must you repeat the content models of 
> all of the earlier base types in the type hierarchy - or do you only 
> need to specify the extended components?
> 
> This is a repetition of an earlier question posted on Dec 18 which has
yet to 
> be answered.
> 
> -------------------------------------------------------
> 
> 8. Is it possible to derive an abstract complexType from a non-abstract
> complexType?
> 
> -------------------------------------------------------
> 
> 9. Using derivation by restriction, can we change the content model of a
group 
> from choice[0,n] to sequence?
> 
> -------------------------------------------------------
> 
> 
> 
> 
> 
> 
*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
    SHIBATA Yoshiaki (柴田 賀昭 in Japanese)
       Sony Corporation, HNC, BBC
       Address: Shinagawa Inter City C Tower
           2-15-3 Konan, Minato-ku, Tokyo, 108-6201 Japan
       Tel: +81-3-5769-5328 Fax: +81-3-5769-5835
Received on Tuesday, 2 January 2001 12:36:35 GMT

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