Are dcterms:references and dc:relation are mutually exclusive

Question

I'm trying to create a schema for an XML document interchange I'm creating, and there are three variations of reference want to indicate

1. Citation (one article cites another)
2. Derivation (research furthering previous experiments)
3. Dependency (reports that depend on data-sets)

To me, these clearly fall into three dcterms elements:

• Number 1 is dcterms:references
• Number 2 should be dc:source
• Number 3 should be dc:relation

The problem is that [according to my Oxygen (v16.0) editor] both the dc:relation and dcterms:relation elements conflict with dcterms:references as they violate "Unique Particle Attribution" rule.

Looking at the dc & dcterms schema - I can't see why this should be (and all the other substitutionGroup="relation" elements from http://www.dublincore.org/schemas/xmls/qdc/dcterms.xsd validate fine.

Is this Oxygen getting it wrong, or is there a definition I'm missing?