The <nvs> element is a container element for the device datapoints defined for each <attribute> element, and is also the container element for the device datapoint definitions contained within an <nvs> element defined within the <device> container element.
<device pid="9FFFFF05006F0002" name="LED" type="color_lamp_controller" brand="Echelon">
<attributes>
<attribute ... >
<nvs>
<nv ... />
</nvs>
</attribute>
</attributes>
<nvs>
<nv ... >
<byte ... >
<attribute ... />
</byte>
</nv>
</nvs>
</device>
<xs:element name="nvs">
<xs:complexType>
<xs:sequence>
<xs:element ref="nv" maxOccurs="4095" />
</xs:sequence>
</xs:complexType>
</xs:element>