search for literal with different language code - sparql

Question

I have two graphs, in one the literals are tagged (#de) in the other untagged. I need a join between the two. The trivial solution with a filter runs very slow.
WHERE {
?tok nlp:lemma ?lem .
?tok2 wn:form ?t .
filter (?tok2 = ?t) .
...
An improved version which works with fuseki is
WHERE {
?tok nlp:lemma ?lem .
Bind (str(?lem) as ?lems) .
?lu :orthForm ?lems .
...
I tried ?lu :xx (str(?lem)) . but this is flagged as an error. Why?
Similarly, using value ?lems {str(?lem)}.
I assume naively that the bind does not create much overhead, thus the above solution probably o.k.
Would the same approach work for searching when the language codes are different my previous question

Answer 1

The only thing allowed in a triple pattern are variables, URIs, literals (in object) and bnodes. Hence instead of the pattern ?lu :xx (str(?lem)), you will need to use a BIND or projection to convert the variable to a string. Taking the first example:
WHERE {
?lu :xx ?langLem .
BIND(str(?langLem) AS ?lem)
}
Or, using projection:
SELECT (str(?langLem) AS ?lem)
WHERE {
?lu :xx ?langLem .
}
I assume you are trying to use the VALUES statement in value ?lems {str(?lem)}. VALUES is normally used to bind variables to a set of values, e.g.:
VALUES ?lem { :Euclid :Gauss }
?lem rdfs:label ?label .
...binds ?lem to :Euclid and :Gauss and executes the query, returning the union of results. I.e. it is the same as:
{ :Euclid rdfs:label ?label }
UNION
{ :Gauss rdfs:label ?label }