获取地方dbpedia的经度和纬度 [英] get latitude and longitude of a place dbpedia
问题描述
我想获取一个我已经知道其名字的地方的经度和纬度
I want to get the latitude and longitude of a place whose name I already know by
PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos#>
PREFIX dbo: <http://dbpedia.org/ontology/>
SELECT * WHERE {
?s a dbo:Place .
?s geo:lat ?lat .
?s geo:long ?long .
}
地点(?s)的名称类似于Graves Park.
在该地名可能会有所不同的耶拿市，如何实施相同的做法?
where the name of the place (?s) is something like Graves Park.
How would one go about implementing the same in Jena where the name of the place might vary?
推荐答案
您可以使用Jena的ARQ对远程SPARQL端点执行查询.该过程在 ARQ中进行了描述-查询远程SPARQL服务.
You can use Jena's ARQ to execute queries against remote SPARQL endpoints. The process is described in ARQ — Querying Remote SPARQL Services.
To do this for different places that you might not know until it is time to execute the query, you can use a ParameterizedSparqlString to hold the query and then inject the value(s) once you have them. Here's an example. The query is the one you provided. I put it into a ParameterizedSparqlString, and then used setIri to set ?s to http://dbpedia.org/resource/Mount_Monadnock.
import com.hp.hpl.jena.query.ParameterizedSparqlString;
import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.query.ResultSetFormatter;
public class DBPediaQuery {
public static void main( String[] args ) {
final String dbpedia = "http://dbpedia.org/sparql";
final ParameterizedSparqlString queryString
= new ParameterizedSparqlString(
"PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos#>"+
"PREFIX dbo: <http://dbpedia.org/ontology/>" +
"SELECT * WHERE {" +
" ?s a dbo:Place ." +
" ?s geo:lat ?lat ." +
" ?s geo:long ?long ." +
"}" );
queryString.setIri( "?s", "http://dbpedia.org/resource/Mount_Monadnock");
QueryExecution exec = QueryExecutionFactory.sparqlService( dbpedia, queryString.toString() );
ResultSet results = exec.execSelect();
ResultSetFormatter.out( System.out, results );
}
}
由此显示的结果是:
--------------------------------------------------------------------------------------------------------------
| lat | long |
==============================================================================================================
| "42.8608"^^<http://www.w3.org/2001/XMLSchema#float> | "-72.1081"^^<http://www.w3.org/2001/XMLSchema#float> |
--------------------------------------------------------------------------------------------------------------
一旦有了ResultSet，就可以遍历解决方案的各行并提取值.此处的值是Literal，并且可以从Literal中提取词汇形式(字符串值)，或者将该值提取为相应的Java类型(对于数字，字符串，布尔值和&c). ).您可以执行以下操作以打印纬度和经度，而不使用ResultSetFormatter:
Once you have the ResultSet, you can iterate through the rows of the solution and extract the values. The values here are Literals, and from a Literal you can extract the lexical form (the string value), or the value as the corresponding Java type (in the case of numbers, strings, booleans, &c.). You could do the the following to print the latitude and longitude instead of using the ResultSetFormatter:
while ( results.hasNext() ) {
QuerySolution solution = results.next();
Literal latitude = solution.getLiteral( "?lat" );
Literal longitude = solution.getLiteral( "?long" );
String sLat = latitude.getLexicalForm();
String sLon = longitude.getLexicalForm();
float fLat = latitude.getFloat();
float fLon = longitude.getFloat();
System.out.println( "Strings: " + sLat + "," + sLon );
System.out.println( "Floats: " + fLat + "," + fLon );
}
此更改后的输出为:
Strings: 42.8608,-72.1081
Floats: 42.8608,-72.1081
在CONSTRUCT查询中使用ParameterizedSparqlStrings
Using ParameterizedSparqlStrings in CONSTRUCT queries
Based some of the comments, it may also be useful to use CONSTRUCT queries to save the results from each query, and to aggregate them into a larger model. Here's code that uses a construct query to retrieve the latitude and longitude of Mount Monadnock and Mount Lafayette, and stores them in a single model. (Here we're just using CONSTRUCT WHERE {…}, so the model that is returned is exactly the same as the part of the graph that matched. You can get different results by using CONSTRUCT {…} WHERE {…}.)
import com.hp.hpl.jena.query.ParameterizedSparqlString;
import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.rdf.model.ModelFactory;
public class DBPediaQuery {
public static void main( String[] args ) {
final String dbpedia = "http://dbpedia.org/sparql";
final ParameterizedSparqlString queryString
= new ParameterizedSparqlString(
"PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos#>"+
"PREFIX dbo: <http://dbpedia.org/ontology/>" +
"CONSTRUCT WHERE {" +
" ?s a dbo:Place ." +
" ?s geo:lat ?lat ." +
" ?s geo:long ?long ." +
"}" );
Model allResults = ModelFactory.createDefaultModel();
for ( String mountain : new String[] { "Mount_Monadnock", "Mount_Lafayette" } ) {
queryString.setIri( "?s", "http://dbpedia.org/resource/" + mountain );
QueryExecution exec = QueryExecutionFactory.sparqlService( dbpedia, queryString.toString() );
Model results = exec.execConstruct();
allResults.add( results );
}
allResults.setNsPrefix( "geo", "http://www.w3.org/2003/01/geo/wgs84_pos#" );
allResults.setNsPrefix( "dbo", "http://dbpedia.org/ontology/" );
allResults.setNsPrefix( "dbr", "http://dbpedia.org/resource/" );
allResults.write( System.out, "N3" );
}
}
输出显示两个查询的三元组:
The output shows triples from both queries:
@prefix dbr: <http://dbpedia.org/resource/> .
@prefix geo: <http://www.w3.org/2003/01/geo/wgs84_pos#> .
@prefix dbo: <http://dbpedia.org/ontology/> .
dbr:Mount_Lafayette
a dbo:Place ;
geo:lat "44.1607"^^<http://www.w3.org/2001/XMLSchema#float> ;
geo:long "-71.6444"^^<http://www.w3.org/2001/XMLSchema#float> .
dbr:Mount_Monadnock
a dbo:Place ;
geo:lat "42.8608"^^<http://www.w3.org/2001/XMLSchema#float> ;
geo:long "-72.1081"^^<http://www.w3.org/2001/XMLSchema#float> .
这篇关于获取地方dbpedia的经度和纬度的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
