## Alternative Implementations The approach was chosen after considering the alternatives demonstrated by other implementations. ### w3c: https://www.w3.org/2009/sparql/wiki/Feature:FullText http://www.w3.org/TR/xpath-full-text-10/ They propose to add a `contains` operator for filters ?s ?p ?o . FILTER ( ?p IN (dct:title, foaf:name, rdfs:label)) . FILTER ( ?o contains 'foo*' ) . or FILTER ( ?o contains ('foo*', constraint) ) . they propose also to adopt xquery text matching syntax. The grammars are https://www.w3.org/TR/xpath-full-text-10/#id-grammar (@197 productions v/s 39 ?) https://www.w3.org/TR/xpath-full-text-10/#id-xpath-grammar (@125 productions v/s 70 https://www.w3.org/TR/xpath20/#nt-bnf) In order for this approach to improive on regular expression filter constraints, it would have to be compiled to generate index results generation rather than scan a filter. ### stardog : https://www.stardog.com/docs https://docs.stardog.com/query-stardog/full-text-search It supports both magic properties and a sub-query form. For magic properties, they follow Jena ```sparql SELECT DISTINCT ?s ?score WHERE { ?s ?p ?l. (?l ?score) ('mac' 100). } ``` in general (term score) (pattern limit) or (term score) (pattern minScore limit) The subquery/service clause form permits more arguments and results. SELECT * WHERE { service fts:textMatch { [] fts:query 'Mexico AND city' ; fts:threshold 0.6 ; fts:limit 10 ; fts:offset 5 ; fts:score ?score ; fts:result ?res ; } } ### jena : https://jena.apache.org/documentation/query/text-query.html says, 'the text index provides an inverted index that maps query string matches to subject URIs' but, in fact, the relation is (subject x graph x string x language) plus an identifier argument (to distinguish predicates ?) PREFIX ex: PREFIX rdfs: PREFIX text: SELECT ?s ?lbl WHERE { ?s a ex:Product ; rdfs:label ?lbl . ( ?s ?score ) text:query (rdfs:label 'printer') ; } This is not complete: the general intent is not to constrain just the text term, but to index the entires statement with an graph context. WHERE { ?s a ex:Product ; ( ?s ?score ?lbl) text:query (rdfs:label 'printer') ; } The general syntax permits literals in the subject position as well ?s text:query 'word' # query ?s text:query ('word' 10) # with limit on results ?s text:query (rdfs:label 'word') # query specific property if multiple ?s text:query (rdfs:label 'protégé' 'lang:fr') # restrict search to French (?s ?score) text:query 'word' # query capturing also the score (?s ?score ?literal) text:query 'word' # ... and original literal value (?s ?score ?literal ?g) text:query 'word' # ... and the graph where the form is further qualified by its appearance in a graph clause. (see https://jena.apache.org/documentation/query/text-query.html#queries-with-graphs) ### dotnet : https://github.com/dotnetrdf/dotnetrdf/wiki/UserGuide-Full-Text-Querying-With-SPARQL It follows ARQ PREFIX pf: SELECT * WHERE { ?match pf:textMatch ( "text" 0.75) . } ### marklogic : https://docs.marklogic.com/guide/semantics/semantic-searches#id_43103 SELECT * WHERE{ ?s ?p ?o . FILTER cts:contains(?o, cts:or-query(("Monarch", "Sovereign"))) FILTER(?p IN (dc:description, rdfs:type)) } ### neptune : https://docs.amazonaws.cn/en_us/neptune/latest/userguide/full-text-search-sparql-examples.html It follows the stardog pattern which expresses the freetext match as a service clause PREFIX foaf: PREFIX neptune-fts: SELECT * WHERE { SERVICE neptune-fts:search { neptune-fts:config neptune-fts:endpoint 'http://your-es-endpoint.com' . neptune-fts:config neptune-fts:queryType 'match' . neptune-fts:config neptune-fts:field foaf:name . neptune-fts:config neptune-fts:query 'michael' . neptune-fts:config neptune-fts:return ?res . } } ### virtuoso : http://docs.openlinksw.com/virtuoso/rdfsparqlrulefulltext/ It relies on `bif:contains` as a "magic predicate", to indicate that the respective object serve as a match pattern. Rather than incorporating additional parameters and results with standard syntax, it handles return properites with an `OPTION` clause PREFIX bif: SELECT * WHERE { ?s ?p ?o . ?o bif:contains 'NEW AND YORK' OPTION (score ?sc) . # this form fails } ORDER BY DESC (?sc) LIMIT 10 ### graphdb : http://graphdb.ontotext.com/documentation/free/full-text-search.html The free text capability is based on Lucene, but extends beyound elementary text 'node' matching to incorporate graph patterns (called 'molecules') into the index itself. These introduce additional bindings directly into the result solutions. Each index is designated by its own predicate. Additional parameters are indicated by specific predicates. A query result includes the subgraph implicated by matched "nodes". PREFIX luc: PREFIX ex: SELECT * { ?node luc:myIndex "lucene query string" . ?node ex:importance ?importance . ?node luc:score ?score . } ORDER BY ( ?score + ?importance )