Hi,

>  I have this structure in XML... 
>  
>  <elements>
>   <element>5</element>
>   <element>3</element>
>   <element>6</element>
>   <element>1</element>
>  </elements>
> 
>  With XSL, i have...
> 
>  <xsl:for-each select="element">
>   <xsl:sort select="." order="ascending" data-type="number"/>
>    ...
>  </xsl:for-each>
> 
>  In this way, the elements have this order...
> 
>  position() = 1 --> element = 1
>  position() = 2 --> element = 3
>  position() = 3 --> element = 5
>  position() = 4 --> element = 6
> 
>  But ...
> 
>  preceding of element = 1 is element = 6
>  preceding of element = 3 is element = 5
>  preceding of element = 5 is element = null
>  preceding of element = 6 is element = 3
> 
>  Then, how i know that preceding of element=3 in the order is 
> the element = 1?
> ¿? 

Unfortenately, you don't. You can either do two passes, first sorting and then going through the elements and testing their preceding element, or sort the elements into a Result Tree Fragment, cast that into a node-set using an extension, and then process them.
  
>  How i calculate the acumulated total?¿? (for the element = 5 
> the total 
> acumulated is 1 + 3 + 5 ...)

You don't need preceding axis for that, just use 

  <xsl:value-of select="sum(../element[. &lt;= current()])"/>

Cheers,

Jarno

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