Grid allows headers to merge, forming groups of columns into meaningful categories.
To achieve this, simply declare the <auxheader> and specify the number of columns the header should span over.

<grid>
	<auxhead>
		<auxheader label="H1'07" colspan="6"/>
		<auxheader label="H2'07" colspan="6"/>
	</auxhead>
	<auxhead>
		<auxheader label="Q1" colspan="3"/>
		<auxheader label="Q2" colspan="3"/>
		<auxheader label="Q3" colspan="3"/>
		<auxheader label="Q4" colspan="3"/>
	</auxhead>
	<columns>
		<column label="Jan"/><column label="Feb"/><column label="Mar"/>
		<column label="Apr"/><column label="May"/><column label="Jun"/>
		<column label="Jul"/><column label="Aug"/><column label="Sep"/>
		<column label="Oct"/><column label="Nov"/><column label="Dec"/>
	</columns>
	<rows>
		<row>
			<label value="1,000"/><label value="1,100"/><label value="1,200"/>
			<label value="1,300"/><label value="1,400"/><label value="1,500"/>
			<label value="1,600"/><label value="1,700"/><label value="1,800"/>
			<label value="1,900"/><label value="2,000"/><label value="2,100"/>
		</row>
		<row>
			<label value="1,500"/><label value="2,100"/><label value="1,200"/>
			<label value="1,100"/><label value="2,400"/><label value="1,700"/>
			<label value="1,500"/><label value="3,700"/><label value="1,800"/>
			<label value="1,300"/><label value="2,000"/><label value="2,500"/>
		</row>
	</rows>
</grid>