Using Query Expansion in REST API calls

An indexed ontolection can be used for query expansion in a REST API call by passing the query-modification-expansion value to the query-modification-macros parameter and supplying the following XML to the extra-xml parameter, with your values substituted in appropriately (at least for INDEXED_ONTOLECTION_NAME and SEARCH_COLLECTION_NAME:

<declare name="query-expansion.enabled" />
<set-var name="query-expansion.enabled">true</set-var>
<declare name="query-expansion.user-profile" />
<set-var name="query-expansion.user-profile">on</set-var>
<declare name="query-expansion.ontolections" />
<set-var name="query-expansion.ontolections">INDEXED_ONTOLECTION_NAME</set-var>
<declare name="query-expansion.max-terms-per-type" />
<set-var name="query-expansion.max-terms-per-type">3</set-var>
<declare name="query-expansion.automatic" />
<set-var name="query-expansion.automatic">related</set-var>
<declare name="query-expansion.suggestion" />
<set-var name="query-expansion.suggestion"></set-var>
<declare name="query-expansion.query-match-type" />
<set-var name="query-expansion.query-match-type">terms</set-var>
<declare name="query-expansion.conceptual-search-similarity-threshold" />
<set-var name="query-expansion.conceptual-search-similarity-threshold">0.1</set-var>
<declare name="query-expansion.conceptual-search-metric" />
<set-var name="query-expansion.conceptual-search-metric">euclidean-dot-product</set-var>
<declare name="query-expansion.conceptual-search-candidates-max" />
<set-var name="query-expansion.conceptual-search-candidates-max">euclidean-dot-product</set-var>
<declare name="query-expansion.conceptual-search-sources" />
<set-var name="query-expansion.conceptual-search-sources">SEARCH_COLLECTION_NAME</set-var>
<declare name="query-expansion.stem-expansions" />
<set-var name="query-expansion.stem-expansions">false</set-var>
<declare name="query-expansion.stemming-weight" />
<set-var name="query-expansion.stemming-weight">0.8</set-var>

To use multiple ontolections, provide a comma- or space-separated list of indexed ontolection names to the query-expansion.ontolections parameter above.