<ROOT>
	<BST>
		<ID>1</ID>
		<GROUP>1</GROUP>
	</BST>
	<BST>
		<ID>2</ID>
		<GROUP>3</GROUP>
	</BST>
	<BST>
		<ID>3</ID>
		<GROUP>2</GROUP>
	</BST>
	<BST>
		<ID>4</ID>
		<GROUP>1</GROUP>
	</BST>
	<BST>
		<ID>5</ID>
		<GROUP>3</GROUP>
	</BST>	
	<BST>
		<ID>6</ID>
		<GROUP>2</GROUP>
	</BST>
	<BST>
		<ID>7</ID>
		<GROUP>1</GROUP>
	</BST>
	<BST>
		<ID>8</ID>
		<GROUP>3</GROUP>
	</BST>	
	<BST>
		<ID>9</ID>
		<GROUP>2</GROUP>
	</BST>	
	<BST>
		<ID>10</ID>
		<GROUP>1</GROUP>
	</BST>	
</ROOT>

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0" xmlns:BSmart="urn:BSmart">
    <xsl:key name="GR" match="BST" use ="GROUP"/>
    <xsl:template match="ROOT">
        <xsl:apply-templates select="BST[generate-id() = generate-id(key('GR', GROUP))]">
			<xsl:sort select="GROUP"  data-type="number" order="ascending"/>
		</xsl:apply-templates>
    </xsl:template>

    <xsl:template match="BST">

        <xsl:for-each select="key('GR', GROUP)">
            <xsl:sort select="ID"  data-type ="number" order="ascending"/>
            <xsl:variable name="curPos">
                <xsl:number count="BST/GROUP" level="any"/>
            </xsl:variable>
            G=<xsl:value-of select="GROUP"/>;POS=<xsl:value-of select="$curPos"/>
        </xsl:for-each >
    </xsl:template>
</xsl:stylesheet>