Keyword Searches
Keyword searches are parsed into a series of terms and operators.
Terms can be a single word —plankton or carbon — or a phrase surrounded by double quotes —"ocean acidification"
Operators allow you to customize the text search in the following ways:
Wildcards
Wildcard searches can be run on individual terms, using:
? to replace a single character:
carbon?te
* to replace zero or more characters:,
ocean acid*
Boolean Operators
The preferred operators are:
+ (this term must be present)
- (this term must not be present)
"coral calcification" +biota -pacific
- biota must be present
- pacific must not be present
- "coral calcification" is optional - its presense increases the relevance
Fuzzy Matching
We can search for terms that are similar to, but not exactly like our search terms, using the "fuzzy" operator: ~. This uses the Damerau-Levenshtein distance to find all terms with a maximum of two changes, where a change is the insertion, deletion or substitution of a single character, or transposition of two adjacent characters. The default edit distance is 2, but you can specify the distance:
"carbon"~3
Proximity Searches
While a phrase query (eg "john smith") expects all of the terms in exactly the same order, a proximity query allows the specified words to be further apart or in a different order. In the same way that fuzzy queries can specify a maximum edit distance for characters in a word, a proximity search allows us to specify a maximum edit distance of words in a phrase:
"primary production"~3