What's the use case for @requires and @policySets on the SCA properties?

Hi,

The assembly spec allows the @requires and
@policySets on SCA properties. What's the use case here?

3990 <!--
Property -->

3991 <complexType
name="SCAPropertyBase"
mixed="true">

3992 <sequence>

3993 <any
namespace="##any"
processContents="lax"
minOccurs="0"/>

3994 <!--
NOT an extension point; This any exists to accept

3995 the
element-based or complex type property

3996 i.e.
no element-based extension point under "sca:property" -->

3997 </sequence>

3998 <!--
mixed="true" to handle simple type -->

3999 <attribute
name="requires"
type="sca:listOfQNames"
use="optional"/>

4000 <attribute
name="policySets"
type="sca:listOfQNames"
use="optional"/>

4001 </complexType>

Thanks,

Raymond
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