Zero Length Element Validation in a Schema

[tim273]

Hello Everyone,

I writing a schema where several elements are required, but but may not have any length. For example:

<CurrencyCode>USD</CurrencyCode>

is valid. But this is also valid:

<CurrencyCode/>

I want to create an element decleration that allows for zero length, but when there is data, it validates that it is a certian type. The example above would be a list currency types, but nulls are also allowed. Here's what I currently have in my schema:

<xs:simpleType name=&quot;currencyCodeType&quot;>
<xs:restriction base=&quot;xs:string&quot;>
<xs:enumeration value=&quot;USD&quot;/>
<xs:enumeration value=&quot;usd&quot;/>
</xs:restriction>
</xs:simpleType>

Any input would be appreicated. Thanks.