XSD Question

I am trying to structure an document schema that has a list of
components, and a list of vendors. Each component "points" to a
particular vendor using a vendor code.
>
Until now, we've just included the vendor code in each component
element. However, I'm trying to move everything into an XSD
specification and I'm wondering if there is a "standard" way to do this,
maybe with something like ID and IDREF?
>
Below is a simplified example of the proprietary XML code we are using
now. Any references or ideas of a better way to do this would be
appreciated.
>
----
>
<components>
.
.
<component>
<partno>74HC123</partno>
<vendorcode>J1321999</vendorcode>
</component>
.
.
</components>
<vendors>
.
.
<vendor>
<name>Arrow</name>
<vendorcode>J1321999</vendorcode>
</vendor>
.
.
</vendors>