Is integer a supported type in custom attribute?

Is "integer" a supported type to be configured on a custom attribute? For example, I can define the following custom attribute of type string, but can I make it of integer type?

<static-configuration-data id="com.ibm.team.workitem.configuration.workItemTypes" xmlns="http://com.ibm.team.workitem/workitemTypes">

<!-- cut out the type definition -->

<customAttributes category="com.ibm.team.workitem.workItemType">
<customAttribute
id="lowerEstimateFromProcessSpec"
type="string"
name="Lower Estimate"
/>
</customAttributes>