Wikidata:Request a query

Request a query

This is a page where SPARQL queries [Q114898838] can be requested. Please provide feedback if a query is written for you.

You can also request help to rewrite queries that don't work anymore, due to the WDQS graph split.

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Help with WDGS

Hi, I have a number of queries written as part of a project Wikidata:WikiProject LSEThesisProject and will need to re-write them due to the Graph Split. My SPARQL knowledge is basic and the queries produced were achieved by trial and error / modifying others' queries / kind help from the community. In preparation for trying to learn how I might re-write those queries I tried, using the Federation Guide, to write federated queries which would pick up all research outputs produced by an academic - this includes not only scholarly articles, but also book chapters, version edition translations, blog posts, chapters and articles. In the main graph as it was all these can be picked up in one query https://w.wiki/B6Ct but I'm failing to re-write this for the scholarly graph. I've tried

SELECT ?item ?itemLabel ?itemType ?itemTypeLabel

WHERE

{

&nbsp; ?item wdt:P50 wd:Q17508688.

&nbsp; SERVICE wdsubgraph:wikidata_main {

&nbsp;&nbsp; ?item wdt:P50 wd:Q17508688.


}

&nbsp; SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],mul,en". } # Helps get the label in your language, if not, then default for all languages, then en language

}

This gives me no results.

And I've tried

SELECT ?item ?itemLabel ?itemType ?itemTypeLabel

WHERE

{

&nbsp; ?item wdt:P50 wd:Q17508688. 

&nbsp; UNION 

&nbsp; { SERVICE wdsubgraph:wikidata_main { ?item wdt:P50 wd:Q17508688}&nbsp; }

&nbsp; &nbsp; 

&nbsp;

&nbsp; SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],mul,en". } # Helps get the label in your language, if not, then default for all languages, then en language

}

Which gives an error message and says the query is malformed at UNION.

Would someone be able to point out what I'm doing wrong and show me how to produce these queries.

Thanks HelsKRW (talk) 08:40, 4 September 2024 (UTC)[reply]

@HelsKRW The UNION requires the parts to be wrapped with curly brackets:

  { ?item wdt:P50 wd:Q17508688. } 
  UNION 
  { SERVICE wdsubgraph:wikidata_main { ?item wdt:P50 wd:Q17508688}  }

Here below should be your query rewritten (to run on https://query-main.wikidata.org/):

SELECT ?item ?itemLabel ?itemType ?itemTypeLabel WHERE {
  VALUES (?author) {(wd:Q17508688)}
  {
    # get the publications from the scholarly subgraph 
    SERVICE wdsubgraph:scholarly_articles {
      ?item wdt:P50 ?author ;
            wdt:P31 ?itemType
      # Instruct the label service to gather the label of the publication
      # The label for ?itemType will be fetched in the host query, the type is probably part of the main graph
      BIND(?itemLabel AS ?itemLabel)
      SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
    }
  } UNION {
    # Union them with the publications in the main graph (blogs, articles...)
    ?item wdt:P50 ?author ;
          wdt:P31 ?itemType
  }  
  SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
}

Try it DCausse (WMF) (talk) 11:28, 4 September 2024 (UTC)[reply]

Thank you very much for your help. I've modified the query I'd written for the scholarly graph which is now working and I can see that the longer query you've written for the main graph is also working. Could you tell me more about how to know when the query should be written on the scholarly graph or the main graph? And would you be able to tell me more about the VALUES, BIND and UNION commands in the query you've written for the main graph. Using this query I've tried modifying some other queries, but I'm hitting up against a series of error messages and despite reading the federated guide am struggling to understand or get to grips with how to write a federated query. Thanks HelsKRW (talk) 10:25, 5 September 2024 (UTC)[reply]

Unfortunately, while writing Wikidata:SPARQL_query_service/WDQS_graph_split/Internal_Federation_Guide I could not find a reasonable and comprehensive set of characteristics to determine if it's better to use query-main or query-scholarly for the host query. Generally both are doable but for certain queries using one or the other greatly impact the complexity of the query.

What I would suggest is perhaps using query-main first (this is the one I most often used when writing Wikidata:SPARQL_query_service/WDQS_graph_split/Federated_Queries_Examples) and consider using query-scholarly if the query happens to be difficult to write. I hope that with more examples we can improve the guide over time.

VALUES is a sparql feature that allows to define a variable, I used it to avoid having to repeat wd:Q17508688 in the two clause around UNION. So that you can change it in single place when willing to see publication of another author.
BIND(?itemLabel AS ?itemLabel) is a trick we use to make the wikibase:label understand that we want to keep the label the of the item, this explained at Wikidata:SPARQL_query_service/WDQS_graph_split/Internal_Federation_Guide#Misplacing_the_label_service. But in general BIND is creating a variable, for instance in place of VALUES (?author) {(wd:Q17508688)} I could've written BIND(wd:Q17508688 as ?author).
UNION allows to collect the information from multiple expressions: { EXPRESSION1 } UNION { EXPRESSION2 }, in the query above EXPRESSION1 extract the scientific publications (?item) and their labels (?itemLabel) from the scholarly subgraph, EXPRESSION2 is collecting the other publications (blogs, articles) from the host service (here serving the wikidata_main graph).DCausse (WMF) (talk) 13:11, 5 September 2024 (UTC)[reply]

Thank you, In practice I seem to be struggling with the UNION command - I've tried it in multiple queries and always get an error message, whatever combination of curly brackets I try!

If I take this query from my thesis project https://w.wiki/5aHL which gives me a list of LSE’s doctoral theses with author links to Wikipedia pages where available, and try to re-write it for the new main graph... I edit it to include the hint optimizer, the SERVICE scholarly graph and BIND – the query runs, but gives me no results https://w.wiki/B7Fj

So I try to add in the UNION command, but whatever I do with curly bracket combinations I get an error message so can’t run the query

SELECT ?thesis ?thesisDescription ?thesisLabel ?author ?authorLabel ?authorwp ?lse_url WHERE {
&nbsp; hint:Query hint:optimizer "None" .
&nbsp; SERVICE wdsubgraph:scholarly_articles {
&nbsp; 
&nbsp; ?thesis wdt:P31/wdt:P279* wd:Q1266946 ;
&nbsp;&nbsp; wdt:P953 ?lse_url.
&nbsp; 
&nbsp; &nbsp; BIND(?thesisLabel AS ?thesisLabel)
&nbsp; &nbsp;&nbsp; SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
&nbsp; }
&nbsp; } UNION {
&nbsp;&nbsp; # Union them with the publications in the main graph (blogs, articles...)
&nbsp; &nbsp; ?thesis wdt:P31/wdt:P279* wd:Q1266946 ;
&nbsp;&nbsp; wdt:P953 ?lse_url.
&nbsp; } 
&nbsp; OPTIONAL {
&nbsp;&nbsp; ?thesis wdt:P50 ?author.
&nbsp;&nbsp; OPTIONAL {
&nbsp; &nbsp;&nbsp; ?authorwp schema:about ?author;
&nbsp; &nbsp; &nbsp; schema:isPartOf https://en.wikipedia.org/.
&nbsp;&nbsp; }
&nbsp; }
FILTER(STRSTARTS(STR(?lse_url), http://etheses.lse.ac.uk))
&nbsp; SERVICE wikibase:label { bd:serviceParam wikibase:language "en". }
}
ORDER BY (?thesisDescription)

Are you able to advise what I’m doing wrong on this one? HelsKRW (talk) 10:10, 6 September 2024 (UTC)[reply]

@HelsKRW Your query is syntactically incorrect because it does not balance the opening and closing curly brackets. With complicated queries like this I highly suggest to use proper wikipedia:Indentation_style to rapidly identify where the problem is.

Every time a curly bracket is opened you indent the next line with 2 spaces to the right, when closing one you remove 2 spaces. Open or close only one curly bracket per line. With your query you could perhaps have identified that the problem happened right before the UNION where you have an extra closing curly bracket.

Similarly when not repeating the subject in the patterns (when using ;) try to align the predicates like this:

?thesis wdt:P31/wdt:P279* wd:Q1266946 ;
        wdt:P953 ?lse_url .

So that it's clearer that the wdt:P953 applies to the ?thesis.

After there was several other things incorrect:

You need the thesis' descriptions which are extracted via the label service, in the federation query you need to instruct this service that you need them with BIND(?thesisDescription AS ?thesisDescription) in the same way you bind the ?thesisLabel or by selecting them in a SELECT
The pattern ?thesis wdt:P50 ?author. matches a triple owned by the publication and thus must also be part of the federated query on the scholarly_article (see Wikidata:SPARQL_query_service/WDQS_graph_split/Internal_Federation_Guide#What_is_where?)
You were select thesis using a property path wdt:P31/wdt:P279* which requires triples from the main graph, this is also explained in the section I linked above
And finally you are returning a variable bound under an OPTIONAL clause, these variables are annoying with federation, see Wikidata:SPARQL_query_service/WDQS_graph_split/Internal_Federation_Guide#Returning_variables_bound_by_OPTIONAL for how we workaround this difficulty.

Please see below your query rewritten with federation (to run on query-main) and some explanations in the comments:

SELECT
  ?thesis
  ?thesisDescription
  ?thesisLabel
  (COALESCE(IF(BOUND(?author), ?author, 'N/A')) AS ?author)
  ?authorLabel (COALESCE(IF(BOUND(?authorwp), ?authorwp, 'N/A')) AS ?authorwp)
  ?lse_url
WHERE {
  hint:Query hint:optimizer "None" .
  # Ideally we want to select thesis with: ?thesis wdt:P31/wdt:P279* wd:Q1266946
  # This property path might require navigating triples in the two subgraphs and thus we can't use it
  # We extract ?thesisType first so that we will match it with a simple pattern ?thesis wdt:P31 ?thesisType
  ?thesisType wdt:P279* wd:Q1266946 .
  {
    SERVICE wdsubgraph:scholarly_articles {
      SELECT ?thesis ?thesisLabel ?thesisDescription ?thesisType ?lse_url (COALESCE(IF(BOUND(?author), ?author, 'N/A')) AS ?author) { 
        ?thesis wdt:P31 ?thesisType ;
                wdt:P953 ?lse_url.
        FILTER(STRSTARTS(STR(?lse_url), "http://etheses.lse.ac.uk"))
        # We return a variable bound in an OPTIONAL clause, we have to be careful here 
        # see https://www.wikidata.org/wiki/Wikidata:SPARQL_query_service/WDQS_graph_split/Internal_Federation_Guide#Returning_variables_bound_by_OPTIONAL
        OPTIONAL { ?thesis wdt:P50 ?author. }
        # No need to use the BIND(?thesisLabel AS ?thesisLabel)/BIND(?thesisDescription AS ?thesisDescription) trick here since we wrap our federated query
        # with a SELECT to workaround issues with the optionally bound ?author variable
        SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
      }    
    }    
  } UNION {
    # Union them with the publications in the main graph (blogs, articles...)
    ?thesis wdt:P31 ?thesisType ;
            wdt:P953 ?lse_url.
    FILTER(STRSTARTS(STR(?lse_url), "http://etheses.lse.ac.uk"))
    OPTIONAL { ?thesis wdt:P50 ?author. }
  }
  OPTIONAL {
    ?authorwp schema:about ?author;
              schema:isPartOf <https://en.wikipedia.org/> .
  }
  SERVICE wikibase:label { bd:serviceParam wikibase:language "en". }
}
ORDER BY (?thesisDescription)

DCausse (WMF) (talk) 13:37, 6 September 2024 (UTC)[reply]

Thank you for this, and all the extra detail to help my learning, which I'm just working through. I've tried on a couple of days to save the query on the main graph, but get a message to say URL shortening failed...and I'm getting that with one other query on the main graph today, though have been able to get shortened URLs for plenty of other queries - is this the place to report that, or somewhere else? Thanks! HelsKRW (talk) 11:22, 12 September 2024 (UTC)[reply]

Unfortunately it is a known limitation that I face myself, I'm not sure how others workaround it but for my part I simply copy/paste the whole URL in wikitext. If I want to show the query in the page I sadly have to repeat it twice:

- once with the mw:Extension:SyntaxHighlight using lang="sparql"

- once by copy/paste the full URL in an external link like: [https://query-main.wikidata.org/#AWFULLY%20LONG%20AND%20UNREADABLE%20URL%20PARAMETERS Try it!]

<syntaxhighlight lang="sparql">
SELECT * {?s ?p ?o} LIMIT 1
</syntaxhighlight>
[https://query-main.wikidata.org/#SELECT%20%2a%20%7B%3Fs%20%3Fp%20%3Fo%7D%20LIMIT%201 Try It!]

Template:SPARQL does not yet support query-main nor query-scholarly but if it does at some point I suppose this might be quite handy. DCausse (WMF) (talk) 06:48, 13 September 2024 (UTC)[reply]

Thank you! HelsKRW (talk) 10:18, 13 September 2024 (UTC)[reply]

Labels for scholarly articles

I took my very simplest query to try to get my head round federated queries. I am looking simply for the count of different types of thesis at an institution. I'm not getting the labels for the type of thesis, even though I think those labels must be in the scholarly subgraph, what am I doing wrong?

SELECT ?thesisType ?thesisTypeLabel (COUNT(?thesisType) AS ?count) WHERE {
  ?thesis wdt:P4101 wd:Q1048626;
    wdt:P31 ?thesisType.
  SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
}
GROUP BY ?thesisType ?thesisTypeLabel
ORDER BY DESC (?count)

Wikidata:Request a query

Help with WDGS

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