Soren Kuula wrote:
> slitvinov@g... wrote:
> 
>> I am learning Relax NG. The problem is that I cannot figure
>> out how to make a schema for a table.
>> In my case I would like to make a table with any name of child
>> elements (columns) but columns should have the same number of
>> child elements (cell). Say this file is valid
> 
> 
> That's not expressible as a regular tree language, so Relax NG can't 
> express it either. In fact, no schema language that I know of can 
> express it.
> 
> Soren

hi,

you should consider an alternate schema technology, such as Active Schema :

the schema :
====================== schema.asl
<?xml version="1.0" encoding="iso-8859-1" ?>
<asl:active-schema
     xmlns:xcl="http://www.inria.fr/xml/active-tags/xcl"
     xmlns:asl="http://www.inria.fr/xml/active-schema"
     xmlns:xs="http://www.w3.org/2001/XMLSchema-datatypes"
     target=""
 >

     <asl:element name="test" root="always">
         <asl:sequence>
             <asl:element ref-elem="table" min-occurs="0" 
max-occurs="unbounded"/>
         </asl:sequence>
     </asl:element>

     <asl:element name="table">
         <asl:sequence>
             <asl:element ref-elem="column" min-occurs="1" 
max-occurs="unbounded"/>
         </asl:sequence>
     </asl:element>

     <asl:element name="column">
         <asl:sequence>
             <xcl:if test="{ asl:element()/preceding-sibling::column }">
                 <xcl:then>
                     <asl:element ref-elem="cell" min-occurs="{ 
$asl:max-occurs }" max-occurs="{ count( asl:element()/../column[1]/cell 
) }"/>
                 </xcl:then>
                 <xcl:else>
                     <asl:element ref-elem="cell" min-occurs="1" 
max-occurs="unbounded"/>
                 </xcl:else>
             </xcl:if>
         </asl:sequence>
     </asl:element>

</asl:active-schema>
=====================
as you might guess, the Active Schema Language differs slightly from 
other schema technologies : most things that are usually hard-coded in 
the schema can be defined contextually
-boundaries can be computed dynamically
-content models can also be computed dynamically
-you can mix declarative sentences with imperative instructions
-the specification defines only 20 tags
-and much more...

notice that unlike schematron, ASL computes content models, which allows 
tools such as editors to predict which element is allowed ; schematron 
is not predictive, it can only warn that a rule has not been followed 
AFTER the user has made the mistake, for example by inserting an element 
that is not allowed

the datas :
===================== datas.xml
<?xml version="1.0" encoding="iso-8859-1"?>
<test>

<!--good-->
     <table>
         <column>
             <cell/>
             <cell/>
         </column>
         <column>
             <cell/>
             <cell/>
          </column>
     </table>
     <table>
         <column>
             <cell/>
             <cell/>
             <cell/>
         </column>
         <column>
             <cell/>
             <cell/>
             <cell/>
          </column>
         <column>
             <cell/>
             <cell/>
             <cell/>
          </column>
     </table>

<!--bad-->
     <table>
         <column>
             <cell/>
             <cell/>
         </column>
         <column>
             <cell/><!--cell missing-->
         </column>
     </table>
     <table>
         <column>
             <cell/>
             <cell/>
         </column>
         <column>
             <cell/>
             <cell/>
         </column>
         <column>
             <cell/>
             <cell/>
             <cell/><!--too much cell-->
         </column>
         <column>
             <cell/><!--cell missing-->
         </column>
     </table>
     <table>
         <!--no column ???-->
         <cell/><!--oops-->
         <cell/><!--oops-->
     </table>

</test>
==========================

the Active Sheet which validates the datas with the schema :
============================== active-sheet.xcl
<?xml version="1.0" encoding="iso-8859-1"?>
<xcl:active-sheet
     xmlns:xcl="http://www.inria.fr/xml/active-tags/xcl"
     xmlns:asl="http://www.inria.fr/xml/active-schema"
 >

     <xcl:parse name="datas" source="datas.xml"/>
     <asl:parse-schema name="schema" source="schema.asl"/>

     <asl:validate schema="{ $schema }" node="{ $datas }" augment="yes" 
deep="yes" report="report"/>

     <xcl:for-each name="err" select="{ $report/* }">
         <xcl:echo value="Error { name( value( $err/@reason-id ) ) }"/>
         <xcl:echo value="     node   : { value( $err/@path/@path ) }"/>
         <xcl:echo value="     rule   : { value( 
$err/@rule-path/@rule-path ) }"/>
     </xcl:for-each>

</xcl:active-sheet>
=====================
you see unusual XPath expressions above, because Active Tags allow to 
use XPath on non-XML object, which is the case of "$err" : an object can 
expose some properties as attributes, which value can be an object can 
expose some properties as attributes, which explain why $err/@path/@path 
is relevant

the output :
=====================
Error asl:elementExpected
      node   : {/test/table[3]/column[2]/}
      rule   : 
{/asl:active-schema/asl:element[3]/asl:sequence/xcl:if/xcl:then/asl:element}
Error asl:noMoreContentAllowed
      node   : {/test/table[4]/column[3]/cell[3]}
      rule   : {/asl:active-schema/asl:element[3]}
Error asl:elementExpected
      node   : {/test/table[4]/column[4]/}
      rule   : 
{/asl:active-schema/asl:element[3]/asl:sequence/xcl:if/xcl:then/asl:element}
Error asl:elementExpected
      node   : {/test/table[5]/cell[1]}
      rule   : {/asl:active-schema/asl:element[2]/asl:sequence/asl:element}
Error asl:noMoreContentAllowed
      node   : {/test/table[5]/cell[1]}
      rule   : {/asl:active-schema/asl:element[2]}
Error asl:noMoreContentAllowed
      node   : {/test/table[5]/cell[2]}
      rule   : {/asl:active-schema/asl:element[2]}

======================
the detailed specification :
http://disc.inria.fr/perso/philippe.poulard/xml/active-tags/active-schema/active-schema.html

the tool that implement all that stuff :
http://reflex.gforge.inria.fr/

you can download RefleX freely and run the given Active Sheet to check 
the XML datas with the Active Schema


-- 
Cordialement,

               ///
              (. .)
  --------ooO--(_)--Ooo--------
|      Philippe Poulard       |
  -----------------------------
  http://reflex.gforge.inria.fr/
        Have the RefleX !