Expanders enable you to broaden the scope of your search. Expanders widen your search by including words related to your keywords. These phrases can include the actual text of the full text results in your search or mapped vocabulary terms to add precision.

Before searching with a expander, call the /edsapi/rest/info endpoint to determine the expanders available when searching the defined set of databases. Expander types and values are passed as parameters to the /edsapi/rest/search endpoint.

Expander Definition in the /edsapi/rest/info Response

The /edsapi/rest/info endpoint returns the available expanders. The following expander types are available:

Thesaurus, Full Text, and Enhanced Subject Precision type expanders are available in the /edsapi/rest/info response below.

<InfoResponseMessage xmlns="http://epnet.com/webservices/EbscoApi/Contracts" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
  <AvailableSearchCriteria>
    <AvailableSorts>…</AvailableSorts>
    <AvailableSearchFields>…</AvailableSearchFields>
    <AvailableExpanders>      
      <AvailableExpander>        
        <Id>relatedsubjects</Id>        
        <Label>Apply equivalent subjects</Label>        
        <AddAction>addexpander(relatedsubjects)</AddAction>        
        <DefaultOn>n</DefaultOn>      
      </AvailableExpander>      
      <AvailableExpander>        
        <Id>thesaurus</Id>        
        <Label>Apply related words</Label>        
        <AddAction>addexpander(thesaurus)</AddAction>        
        <DefaultOn>n</DefaultOn>      
      </AvailableExpander>      
      <AvailableExpander>        
        <Id>fulltext</Id>        
        <Label>Also search within the full text of the articles</Label>        
        <AddAction>addexpander(fulltext)</AddAction>        
        <DefaultOn>y</DefaultOn>      
      </AvailableExpander>    
    </AvailableExpanders>    
    <AvailableLimiters>…</AvailableLimiters>
    <AvailableSearchModes>…</AvailableSearchModes>
    <AvailableRelatedContent>…</AvailableRelatedContent>
    <AvailableDidYouMeanOptions>
      <AvailableDidYouMeanOption>
        <Id>AutoSuggest</Id>
        <Label>Did You Mean</Label>
        <DefaultOn>y</DefaultOn>
      </AvailableDidYouMeanOption>
    </AvailableDidYouMeanOptions>
  </AvailableSearchCriteria>
  <ViewResultSettings>
    <ResultsPerPage>20</ResultsPerPage>
    <ResultListView>brief</ResultListView>
  </ViewResultSettings>
  <ApplicationSettings>
    <SessionTimeout>480</SessionTimeout>
  </ApplicationSettings>
  <ApiSettings>
    <MaxRecordJumpAhead>250</MaxRecordJumpAhead>
  </ApiSettings>
</InfoResponseMessage>

Expander Search Specification

When an expander is used in a search, it broadens the scope of a search. Expanders widen the search to include words related to your keywords. When searching with an expander, the user must specify to the /edsapi/rest/search endpoint the type of expander. The type of expander is specified by setting the expander parameter for the /edsapi/rest/search endpoint to an expander type.

Example Search Request with Expander

GET /edsapi/rest/search?query=oil&searchmode=all&resultsperpage=20&pagenumber=1&sort=relevance&highlight=y&includefacets=y&view=brief&autosuggest=n&expander=thesaurus

Example Response Snippet with Full Text Expander

<ExpandersWithAction>
        <ExpanderWithAction>
          <Id>fulltext</Id>
          <RemoveAction>removeexpander(fulltext)</RemoveAction>
        </ExpanderWithAction>
</ExpandersWithAction>

A RemoveAction for the expander selected will be present in the response data. The RemoveAction specifies the action that will remove the expander from the currently specified search.

Expander Points to Note

• Expansions are limited to unqualified keyword searches. If you use specific search tags (field codes) in your search, then equivalent subject expansions will not apply to the search terms preceded by a search tag.
• Not every search gets expanded to equivalent subjects. When Apply Equivalent Subjects is ON, it doesn't mean every search gets an expansion; the search has to match a concept in order to expand to equivalent subjects.
• Not every database is searched with equivalent subjects. When a search matches a concept, it doesn't mean every database is searched with the concept expansion; the expansion only applies to searches against databases that use the mapped vocabularies.
• Not every field is searched with equivalent subjects terms. When a search matches a concept, only a specific subject field is searched for the concept; the expanded terms are not searched in the title or abstract or any other field.