Want to update default value in an enum attribute within the schema

Hi,

I want to update "LVL1" as the default string value in the attribute "current level", the attribute contains enumeration values, i am using the below code but not able to reflect the default values in schema for records having blank "current level".

<enumeration basetype="string" name="currentLevel">
<value label="LVL1" name="tierLVL1" value="LVL1"/>
<value label="LVL2" name="tierLVL2" value="LVL2"/>
<value label="LVL3" name="tierLVL3" value="LVL3"/>
</enumeration>

<element autopk="false" label="Event Log Customer Parameter" name="eventLogCustomerParameter">

<attribute default="LVL1" enum="currentLevel" label="Current Level" length="64" name="currentLevel" required="true" type="string"/>

</element>

Please provide solutions for this. currently i am getting blank in the "current level" attribute with above code.