Hi Hans-Jürgen, You are right. I’ve created an issue to get this fixed [1].
Best, Christian [1] https://github.com/BaseXdb/basex/issues/2141 On Tue, Sep 13, 2022 at 4:43 PM Hans-Juergen Rennau <hren...@yahoo.de> wrote: > > Dear BaseX people, > > it seems to me there is a bug concerning Full Text Search, using option > "window": > > let $text1 := '1 The usability of a Web site is how well the site' > let $text2 := '2 The usability of a Web site is how well the sitx' > let $text3 := '3 The usability of a Web site is how well the site' > return ( > $text1[. contains text 'usability web site' all words window 5 words], > $text2[. contains text 'usability web site' all words window 5 words], > $text3[. contains text 'usability web site' all words window 10 words] > ) > > This query should return all three, $text1, $text2 and $text3, but it only > returns $text2 and $text3. > > So it seems to me that the implemented logic is: "all matches of the "all > words" search must be within a 5-words window, but it should be "there is a > match of the "all words" search which is within a 5-words window. More > detailed argument in PS. > > Kind regards, > Hans-Jürgen > > PS: Compare https://www.w3.org/TR/xpath-full-text-30/#ftwindow > > "A window selection examines the matches generated by the preceding portion > of the FTSelection, and selects those for which the matched tokens and > phrases (more precisely, the individual StringIncludes of that match) are all > found within a window whose size is a specified number of FTUnits (words, > sentences, or paragraphs); for each such window, the window selection then > generates a match containing the merge of those StringIncludes, plus any > StringExcludes that fall within the window." > > (Italic added by me) > > The detailed semantics are given in 4.2.4 FTWords [1]. Pseudo-function > fts:applyFtWordsAllWord() constructs for each of the words an fts:allMatches > element and then performs conjunction of these elements, based on recursive > application of 4.3.6.2 FTAnd [2]. Each fts:allMatches element contains one > fts:match element for each occurrence of the word in question. The "ANDing" > of two fts:allMatches is described by pseudo-function fts:ApplyFTAnd(), which > creates one match for each pair of matches found in the operands - in other > words, all combinations of operand matches are considered. > > As an example consider: > "foo bar" all words > > and assume "foo" occurs two times and "bar" occurs two times. The > fts:allMatches element representing the result is the result of applying > fts:ApplyFTAnd() to two fts:allMatches elements, one obtained for word "foo", > one obtained for word "bar". Schematically: > > $fts:allMatches_foo: > <fts:match>foo(1)</fts:match> > <fts:match>foo(2)</fts:match> > > $fts:allMatches_bar: > <fts:match>bar(1)</fts:match> > <fts:match>bar(2)</fts:match> > > fts:applyFTAnd($fts:allMatches_foo, $fts:allMatches_bar) is a single > fts:allMatches containing four matches, each one of which is a combination of > matches found in the operands: > > <fts:allMatches_allwords> = > <fts:match>foo(1), bar(1)</fts:match> > <fts:match>foo(1), bar(2)</fts:match> > <fts:match>foo(2), bar(1)</fts:match> > <fts:match>foo(2), bar(2)</fts:match> > > Now extend the query to > "foo bar" all words window 5 words > > The result is true, if there is at least one combination of occurrences of > "foo" and "bar" found in a window of at most 5 for word "bar". Referring to > the semantic intermediates: if <fts:allMatches_allwords> contains at least > one <fts:match> element for which all contained matches satisfy the window > condition. > > [1] https://www.w3.org/TR/xpath-full-text-30/#tq-ft-fs-FTWords > [2] https://www.w3.org/TR/xpath-full-text-30/#tq-ft-fs-FTAnd > > > > > > > > > > > > > > > > >
