[Tracker] How to search on matching multiple tags (DC:Keywords)?

[Jimmy Huang <jimmy huang linux intel com>]

I am new to Tracker.  I played around with the RDF to support multiple
keywords with no luck (see below), did I do it right or it doesn't
support search matching multiple tags at the moment? Does anyone here
know to do this?

Contains don't work below

<rdfq:Condition>
  <rdfq:and>

    <rdfq:contains>
      <rdfq:Property name="DC:Keywords" />
      <rdf:String>foo</rdf:String> 
    </rdfq:contains>

    <rdfq:contains>
      <rdfq:Property name="DC:Keywords" />
      <rdf:String>bar</rdf:String> 
    </rdfq:contains>

  </rdfq:and>
</rdfq:Condition>

inSet don't work also

<rdfq:Condition>
  <rdfq:and>

    <rdfq:inSet>
      <rdfq:Property name="DC:Keywords" />
      <rdf:String>foo</rdf:String> 
    </rdfq:inSet>

    <rdfq:inSet>
      <rdfq:Property name="DC:Keywords" />
      <rdf:String>bar</rdf:String> 
    </rdfq:inSet>

  </rdfq:and>
</rdfq:Condition>

inSet with list style works as a conditional OR, and returns results
matching either keyword, but I want a conditional AND instead

<rdfq:Condition>
    <rdfq:inSet>
      <rdfq:Property name="DC:Keywords" />
      <rdf:String>foo,bar</rdf:String> 
    </rdfq:inSet>
</rdfq:Condition>