Rank by Boolean Expr BM25

Ranks objects in SOURCE [OBJ,STRING] according to the relevance score of each STRING with the expression in QUERY [STRING]. The relevance is computed using Okapi BM-25 ranking method.

• SOURCE [OBJ,STRING]: a 2-column input with an object-string pair. Typically obtained with the Extract string block

• RESULT [OBJ]: a list of ranked objects

• Query: a boolean query
• Stemming: tokens can be stemmed for a specific language or left as they are
• Case-sensitive: if set to false, upper/lower case is ignored
• Normalize diacritics: transliterates non-ASCII characters into their closest ASCII form
• Tokenization: the method to tokenize the input strings.
  • None: perform no tokenization
  • Spaces: all valid Unicode space characters
  • Spaces/Punctuation: Spaces + all valid Unicode punctuation characters
  • Spaces/Punctuation/Digits: Spaces/Punctuation + all valid Unicode digit characters
  • Spaces/Punctuation/Digits/Symbols: Spaces/Punctuation/Digits + all valid Unicode symbol characters
  • Custom Regular Expression: any regular expression
• Min token length: tokens whose character length is shorter than this value are discarded
• All query terms must match: if set to true, only candidates where all tokens in QTERMS match a string in SOURCE are considered a match
• k1: controls non-linear term frequency normalisation (saturation). Lower value = quicker saturation (term frequency is more quickly less important)
• b: degree of document-length normalisation applied. 0=no normalisation, 1=full normalisation