pb with labelling of optional variable

[lvaudor]

Hi,

I've encountered an HTTP 500 Internal Server Error with this query:

query=spq_init() %>%                     
  spq_add("?film wdt:P31 wd:Q11424") %>% 
  spq_add("?film wdt:P840 ?loc") %>%            
  spq_add("?loc wdt:P625 ?coords") %>%  
  spq_add("?film wdt:P3383 ?image") %>% 
  spq_add("?film wdt:P921 ?subject", .required=FALSE) %>%          
  spq_add("?film wdt:P577 ?date") %>%   
  spq_label(film,loc,subject) %>%    # <- here, remove subject and it works
  spq_head(10) %>% 
  spq_perform()

while the same query without trying to label "subject" works fine. I guess it has something to do with the fact that subject is optional so labelling it should be too?

[maelle]

it doesn't work either if we make the label optional, that's bad

[maelle]

This would work:

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT ?coords ?date ?film (COALESCE(?film_labell,'') AS ?film_label)
?image ?loc (COALESCE(?loc_labell,'') AS ?loc_label) ?subject
(COALESCE(?subject_labell,'') AS ?subject_label)
WHERE {

?film wdt:P31 wd:Q11424.
?film wdt:P840 ?loc.
?loc wdt:P625 ?coords.
?film wdt:P3383 ?image.
OPTIONAL {
  ?film wdt:P921 ?subject.
?subject rdfs:label ?subject_labell.
FILTER(lang(?subject_labell) IN ('en'))
}
?film wdt:P577 ?date.
OPTIONAL {
?film rdfs:label ?film_labell.
FILTER(lang(?film_labell) IN ('en'))
}

OPTIONAL {
?loc rdfs:label ?loc_labell.
FILTER(lang(?loc_labell) IN ('en'))
}

}

LIMIT 10

Putting the label in the same optional curly thing, however how would we guess a triple defines a variable whose label we want?

[maelle]

Should we add a heuristic of some sort

if we want to label variable X and it only appears in an optional triple, we put the label there?

But we generally don't handle any grouping at all at the moment.

[lvaudor]

query$triples shows that "?film blabla ?subject" is optional, subject is not in any other non-optional triple, so subject is the optional element, not film... Would that make sense?

[lvaudor]

haha same time

[maelle]

Right, so would it make sense to add this, even if we don't handle any other grouping/subqueries kind of things?

[lvaudor]

Yes, I think so

[maelle]

with #205

library("glitter")
spq_init() %>%                     
  spq_add("?film wdt:P31 wd:Q11424") %>% 
  spq_add("?film wdt:P840 ?loc") %>%            
  spq_add("?loc wdt:P625 ?coords") %>%  
  spq_add("?film wdt:P3383 ?image") %>% 
  spq_add("?film wdt:P921 ?subject", .required=FALSE) %>%          
  spq_add("?film wdt:P577 ?date") %>%   
  spq_label(film,loc,subject) %>%
  spq_head(10) %>%
  spq_perform()
#> # A tibble: 10 × 8
#>    film              image loc   coords date                film_label loc_label
#>    <chr>             <chr> <chr> <chr>  <dttm>              <chr>      <chr>    
#>  1 http://www.wikid… http… http… Point… 2015-01-01 00:00:00 Diary of … France   
#>  2 http://www.wikid… http… http… Point… 2015-02-07 00:00:00 Diary of … France   
#>  3 http://www.wikid… http… http… Point… 2015-04-01 00:00:00 Diary of … France   
#>  4 http://www.wikid… http… http… Point… 2015-04-16 00:00:00 Diary of … France   
#>  5 http://www.wikid… http… http… Point… 2015-04-24 00:00:00 Diary of … France   
#>  6 http://www.wikid… http… http… Point… 2015-05-13 00:00:00 Diary of … France   
#>  7 http://www.wikid… http… http… Point… 2015-05-29 00:00:00 Diary of … France   
#>  8 http://www.wikid… http… http… Point… 2015-07-10 00:00:00 Diary of … France   
#>  9 http://www.wikid… http… http… Point… 2015-07-15 00:00:00 Diary of … France   
#> 10 http://www.wikid… http… http… Point… 2016-01-07 00:00:00 Diary of … France   
#> # ℹ 1 more variable: subject_label <chr>

^{Created on 2023-10-19 with reprex v2.0.2}