Extract Chemical Data from DBpedia via SPARQL

问题:

I'd like to know how to submit a SPARQL query to DDBpedia and be given back a table that includes the information found in the Wikipedia "chembox" info box template, such as molecular weight or formula.

So, the first step was just to make a query whose results should be a list of chemical substances that had the formula and molecularWeight properties included. But the following returns no results:

SELECT * WHERE {
  ?y rdf:type dbpedia-owl:ChemicalSubstance.
  ?y rdfs:label ?Name .
  ?y dbpedia:molecularWeight ?molecularWeight .
  ?y dbpedia:formula ?formula .
  OPTIONAL {?y dbpedia-owl:iupacName ?iupacname} .
  FILTER (langMatches(lang(?Name),"en"))
}
LIMIT 50

SPARQL Explorer at dbpedia.org

And so I'm stuck. Is something wrong with this query or does DBPedia really not collect that information from the Wikipedia chemboxes?

回答1:

You caught the wrong namespace for both dbpedia:molecularWeight and dbpedia:formula. The correct namespace here would be dbpedia2.

Furthermore, there seem rarely any entries having a dbpedia-owl:iupacName, dbpedia2:molecularWeight and dbpedia2:formula.

SELECT * WHERE {
  ?y rdf:type dbpedia-owl:ChemicalSubstance.
  ?y rdfs:label ?Name .
  OPTIONAL {?y dbpedia2:formula ?formula }.
  OPTIONAL {?y dbpedia2:molecularWeight ?molecularWeight}.
  OPTIONAL {?y dbpedia-owl:iupacName ?iupacname} .
  FILTER (langMatches(lang(?Name),"en"))
}
LIMIT 50

SPARQL Explorer @dbpedia.org

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To get the correct namespaces, you could either look at one example like this or get a list of all used properties for type dbpedia-owl:ChemicalSubstance using

SELECT DISTINCT ?rel WHERE {
  ?y rdf:type dbpedia-owl:ChemicalSubstance.
  ?y ?rel ?x
}

SPARQL Explorer @dbpedia.org