sparql

问题 I am trying to practice myself in writing some SPARQL queries. Does anybody know where I can find the best material? Where I can find some RDF file and some tasks to try to write my own SPARQL queries. I am good with SQL, and I just need some material to learn to write in SPARQL. 回答1: All sample RDF and queries from the O'Reilly book "Learning SPARQL" are available on the book's home page at learningsparql.com. (Full disclosure: I wrote it.) 回答2: data.gov and DataHub have a lot of

问题 I send the following http request to Sesame Server: params = { 'subj' : '?s', 'pred' : 'rdf:type', 'obj' : 'Device' } Also tried: params = { 'pred' : 'rdf:type', 'obj' : 'Device' } which translates to: http://example.com/openrdf-sesame/repositories/devices/statements?pred=rdf%3Atype&subj=%3Fs&obj=Device I perform following operation on params in PYTHON: urllib.urlencode(params)) I get Response: 400 (Bad Request). Please help resolving this issue. I think its related to improper encoding of

问题 By using DBpedia Spotlight, I get DBpedia URIs. For example http://dbpedia.org/resource/Part-of-speech_tagging I need to request this URI in Java so that it can return me some json/xml and I can fetch the necessary information from the response. For example, in the above mentioned URI, I need the value of dct:subject Below is the screenshot of the response what I get in the browser. 回答1: There isn't enough info in your question about what you're trying to achieve to provide the best path by

问题 I have a fairly complex SPARQL query with the structure outlined below, involving multiple graph patterns, UNION and nested FILTER NOT EXISTS . I want the query to remain generic, and I want to be able to inject values for certain variables at execution time, and my idea is to append a VALUES keyword at the end of the query to specify the value of certain variables in the query. In the structure below, I set the value of ?x , and I illustrate all the places in the query where ?x applies.

问题 I want to check if the graph exists in my Fuseki server and if it does, it should return a message like The graph exists 回答1: You can do this with an ASK query. For example, to check that a named graph http://example.org/graph1 exists, you can do this: ASK WHERE { GRAPH <http://example.org/graph1> { ?s ?p ?o } } It will return true if it exists, false otherwise. 来源： https://stackoverflow.com/questions/27080839/what-is-the-sparql-query-to-check-if-a-graph-exists-and-return-a-message

问题 My query (excerpt) is roughly this. CONSTRUCT { ?publication fb:type ?type; fb:publicationType ?publicationType; } WHERE { ?publication a bibo:Document . ?publication vitro:mostSpecificType ?publicationType . } And it returns output similar to... <rdf:Description rdf:about="https://abcd.fgh/individual/publication12345"> <fb:publication>Example pub title</fb:publication> <fb:publicationType rdf:resource="http://purl.org/ontology/bibo/AcademicArticle"/> </rdf:Description> Perhaps a beginner

问题 Not familiar with semantic web, under the following context: // owl in terms of Java-like syntax Class Person {} Class GraduateStudent extends Person {reference takesCourse [*] : GraduateCourse} Class Student intersect Person {reference takesCourse [*] : Course} Class UndergradStudent extends Student {} Class Course{} Class GraduateCourse extends Course{} Class CsCourse extends Course{} My question is why Q1 ⊑ Q2 does not hold? In particular, if I understand correctly, Q1 select undergraduate

问题 I have a SPARQL query and I want to replace some of the URIs it contains based on a dictionary. I constructed a AbstractQueryModelVisitor that does that, i.e., it substitutes the URIs I want. But once they are substituted, I'm not sure how to get back the string representation of the SPARQL query. I only have the ParsedQuery or TupleExpr of it. Is it possible to convert these representations back to a String representation? Thank you 回答1: There is a SPARQLQueryRenderer class which can convert

问题 I have an instance of Wikibase running. I'm able to run federated queries with Wikidata successfully. I have certain queries that compare labels like this: PREFIX xwdt: <http://www.wikidata.org/prop/direct/> PREFIX xwd: <http://www.wikidata.org/entity/> PREFIX xpq: <http://www.wikidata.org/prop/qualifier/> PREFIX xps: <http://www.wikidata.org/prop/statement/> PREFIX xp: <http://www.wikidata.org/prop/> select ?item ?wditem ?itemLabel ?wid ?wditemlabel where { ?item wdt:P17 wd:Q39. ?item wdt

问题 I try to construct a SPARQL query, where I get a list of skyscrapers with a height of more then 500 meters. I realized, that the property height (P2048) is measured in different units (meter, foot, centimeter). This would not be a problem for me to calculate the different units into meters. But my problem is to figure out, that unit is used for the property height. So my question: how can I get the unit for the property height? My query so far, where ?unit is just empty: SELECT ?skyscraper