Interaction with the Resource Index.
The idea is to search a GSearch index by embedding a Lucene query in an iTQL query ,
and the opposite, to search the Resource Index by embedding an iTQL query in a Lucene query.
Example of iTQL query with embedded Lucene query:
select $object1 $object2 from <#ri>
where $object1 <fedora-model:hasModel> <info:fedora/MyNS:XContentModel>
and $object1 <fgsearch-MyIndex:matches> 'author:Jones AND fulltext:(salt AND water)'
and $object2 <fedora-model:hasModel> <info:fedora/MyNS:YContentModel>
and $object1 <my-model:hasRelationTo> $object2
This overcomes the two weaknesses that Lucene cannot do joins,
and that the full-text option of the Resource Index uses Lucene in a limited manner
(e.g. you cannot search on the full document text behind a pdf datastream,
and you cannot exploit numerous features of Lucene and Solr).