semantic-web | 易学教程

Open world assumption and SPARQL in triple stores

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I would like to know if SPARQL, by default, adopts the open world assumption or if this depends on the triple stores that execute the SPARQL queries. And what are the implications of this assumption in queries. Best regards. Well.... I wonder whether this is really a good question for this site. I think not, but I'm gonna throw a few cents into the bucket anyway. To start with -- does it matter whether SPARQL "adopts" (and what does that mean, to you?) OWA, and, if so, why? Then, to address @AKSW's comment -- W3 differs with @AKSW's assertion, in at least the RDF 1.0 Spec (granted, that has

Sparql Keys vs distinct values

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问题 I have a sparql query that returns duplicates, and I want it to clean them up on one of the values only (subjectID). Unlike DISTINCT that seems to find a unique value for the combination of values selected, rather than for only one of the parameters. I saw someone here propose group by, but that only seems applicable if I list all the parameters after group by (my sparql endpoint complains, e.g. Non-group key variable in SELECT: ?occupation). I tried running an internal select, but it doesn't

Stand alone Application for Retrieving data from 8 ontology files(.ttl files) and displaying the output in json

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问题 I am new to semantic web. I spent lot of time in understanding the concepts of semantic web i.e. RDF,ontology,ontology mapping etc. Now I have a task to retrieve the data from 8 ontology files and display the output in json format. I will explain the problem in detail. I was given 8 ontology files(.ttl files) which represents the information of the persons in an organisation. Now the out put must include the information regarding all the persons in the company with their personal information

WHOIS fields translated to semantic

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问题 There are a lot of "good" WHOIS interpreters, like python-whois or phpWhois, but each has its own interpretation of the fields and use different JSON fields and JSON structures... I am looking for a "Rosetta Stone" semantic tool... It exists? Any sematic jargon as SchemaOrg or free RDF/JSON-LD/etc. interpretion, mapping fields of the raw whois file into its semantic. Exemples of most frequent semantic usage , and its fieldName-to-Semantic mapping: WHOIS field domain is wikidata/Q32635 or

How to install SILK workbench?

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问题 I want to install Silk - The Linked Data Integration Framework. I have downloaded latest version (2.6.1) of SILK WorkBench (https://github.com/silk-framework/silk/releases). I want to install it in both Mac and Windows Machine. Project README file is saying that "The bin-folder contains scripts for running the Silk Workbench on Windows, Linux and iOS." I have tried to run silk-workbench.bat file. However it is giving me following errors. Mac: ./silk-workbench.bat: line 1: @REM: command not

Using jena for creating RDF from XMl file [duplicate]

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问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: create RDF from XML I am sorry for asking this question for the second time, I am still still having problem in generating rdf from the following xml file. <xml> <person> <name>Joe</name> <website url="www.example1.com">contact1</website > <vote>20</vote> </person> <person> <name>Anna</name> <website url="www.example2.com">contact2</website> <vote>80</vote> </person> </xml> I think using jena might solve the

Error while querying DBPedia using Apache Jena

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问题 import java.sql.ResultSet; import java.sql.SQLException; import com.hp.hpl.jena.query.QueryExecution; import com.hp.hpl.jena.query.QueryExecutionFactory; import com.hp.hpl.jena.query.QueryFactory; import com.hp.hpl.jena.query.QuerySolution; import com.hp.hpl.jena.query.ResultSetFormatter; public class sparq { public static void main (String[] args) throws SQLException { String queryString= "PREFIX dbpedia: <http://dbpedia.org/resource/>"+ "PREFIX category: <http://dbpedia.org/resource

SPARQL federated query not working

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问题 My basic issue is: I have two computers A and B with Virtuoso installed and I am trying to query from one computer to the next. I created an RDF graph on machine A and executed a query on A to see the locally stored data. sparql SELECT ?a ?b ?c FROM <http://localhost:8890/test> OPTION (get:soft "soft", get:method "GET") WHERE {?a ?b ?c}; It returned the data correctly. I run the following query on machine B sparql SELECT ?a ?b ?c FROM <http://ipAddressOfA:8890/test> OPTION (get:soft "soft",

Why is owl:Restriction reasoning not working in Blazegraph?

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问题 With the following RDF in Blazegraph (taken from this answer): :eats rdf:type owl:ObjectProperty . :Vegetable rdf:type owl:Class ; rdfs:subClassOf owl:Thing . :Vegetarian rdf:type owl:Class ; owl:equivalentClass [ rdf:type owl:Restriction ; owl:onProperty :eats ; owl:someValuesFrom :Vegetable ] . :Carrot rdf:type :Vegetable , owl:NamedIndividual . :John rdf:type owl:NamedIndividual , owl:Thing ; :eats :carrot . the following SPARQL is returning blank: select ?who where { ?who a :Vegetarian .

Linked Data (RDF) Content Negotiation with apache

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问题 I was wondering if someone could provide me with the typical rule, to serve the appropriate file when a resource is requested, with respect to the content type required. To be more specific here is my situation: I have a purl URL that i redirect to an URL on my apache server. I would like to resource URL to be like a generic URL for the resource, and then serve the appropriate doc depending on the content Type: RDF, TTL, or HTML. Hence i would like to know how to do that within the .htaccess