query-963f7eeae12f3d178a45010a1c472ffb

rq turtle/ttl

TODO

Use at

• https://query.wikidata.org/sparql

PREFIX wikibase: <http://wikiba.se/ontology#>
PREFIX wdt: <http://www.wikidata.org/prop/direct/>
PREFIX wd: <http://www.wikidata.org/entity/>
PREFIX psv: <http://www.wikidata.org/prop/statement/value/>
PREFIX ps: <http://www.wikidata.org/prop/statement/>
PREFIX pq: <http://www.wikidata.org/prop/qualifier/>
PREFIX p: <http://www.wikidata.org/prop/>
PREFIX geo: <http://www.opengis.net/ont/geosparql#>
PREFIX bd: <http://www.bigdata.com/rdf#>
# Note : this query uses the NamedSubquery feature, see https://wiki.blazegraph.com/wiki/index.php/NamedSubquery

#defaultView:Map{"hide":["?coordinates", "?line", "?rgb"]}
SELECT ?coordinates ?line ?station ?itemLabel ?connectLabel ?image ?opening ?rgb

# subquery that selects all stations of the amsterdam metro

#subquery that selects all the lines of the amsterdam metro

WHERE {
  # using an union of the two result sets in there so that each metro station and each metro line has its own unique result line in the final result set. 
  # (In "metro stations" result set, the "?line" variable will be always unbound, 
  #  and conversely in the "metro lines" result set, only the "?line" variable will have a value)
  {  {
  # There may be several images and several coordinates for a station, so we use a « group by » to ensure we have only one line per station in the results
  SELECT ?station (SAMPLE(?coordinates) AS ?coordinates) (SAMPLE(?image) AS ?image) ?opening WHERE {
    ?station wdt:P31/wdt:P279* wd:Q55488 ; # we get train stations
             wdt:P361 wd:Q260870 ;         # … that are part of the amsterdam metro
             wdt:P625 ?coordinates  .      # … their coordinate
    OPTIONAL { ?station wdt:P1619 ?opening }          # … and their opening date
  } GROUP BY ?station ?opening
}} UNION {  {
  SELECT ?line ?connect ?rgb WHERE {
    # we reuse the stations computed by the other named query
     {
  # There may be several images and several coordinates for a station, so we use a « group by » to ensure we have only one line per station in the results
  SELECT ?station (SAMPLE(?coordinates) AS ?coordinates) (SAMPLE(?image) AS ?image) ?opening WHERE {
    ?station wdt:P31/wdt:P279* wd:Q55488 ; # we get train stations
             wdt:P361 wd:Q260870 ;         # … that are part of the amsterdam metro
             wdt:P625 ?coordinates  .      # … their coordinate
    OPTIONAL { ?station wdt:P1619 ?opening }          # … and their opening date
  } GROUP BY ?station ?opening
}.

    ?station p:P197 [ ps:P197 ?nextstation ;           # … we get all the neighbourstation(s) of one station
                      pq:P81  ?connect ] .  
    ?connect wdt:P361 wd:Q260870 ;                     # … who have a transport line that is a part of the amsterdam metro
             wdt:P465 ?rgb                             # … also get the standard colour for the connecting line

    FILTER(STR(?station) < STR(?nextstation)) . # making sure we draw only one line for each pair of neighbour station, 
                                             # (as P197 (neighboor station) is symmetric, we could have two results for each line :
                                             # 1) ?item = Qaaa and ?nextstation = Qbbb 
                                             # 2) ?item = Qbbb and ?nextstation = Qaaa
                                             # so we choose to keep only (arbitrarily) the first one to draw only one line

    ?station     p:P625 / psv:P625 [ wikibase:geoLatitude ?lat1 ;  wikibase:geoLongitude ?lon1 ].      # the coordinates of one end of the line
    ?nextstation p:P625 / psv:P625 [ wikibase:geoLatitude ?lat2 ; wikibase:geoLongitude ?lon2 ].       #               … of one the other end of the line

    # Building the « LINESTRING » instruction that will ask the view to draw a line frome one station to another, 
    BIND(CONCAT('LINESTRING (', STR(?lon1), ' ', STR(?lat1), ',', STR(?lon2), ' ', STR(?lat2), ')') AS ?str) .
    # with the appropriate datatype for the line to be interpreted as such by the map engine 
    # (thanks to strdt : https://www.w3.org/TR/sparql11-query/#func-strdt )
    BIND(STRDT(?str, geo:wktLiteral) AS ?line)
  }
}} .
  # (more naive approach where lines and stations are mixed-up in the same result set lines make some station dots bigger than others)
  SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
}

Query found at

• https://www.wikidata.org/wiki/Wikidata:Request_a_query/Archive/2018/10