Does the ontology have to be posted online for instance? I found on StackOverflow that the URI I assign to the prefix does not have to be a real one. Therefore the URI for the PREFIX cv: "PREFIX cv:< http://www.semanticweb.org/toshiba/ontologies/2017/3/untitled-ontology-6#>" is the one generated by Protege. Did I misunderstand what I read and the ontology needs to be posted publically online?
It is just that I think that the problem may be that in the queries the PREFIX called cv may be perceived as empty by the code or something. On Wed, Jun 7, 2017 at 12:58 PM, Aya Hamdy <[email protected]> wrote: > Sorry about the x, It was a stupid mistake. But it is nit the cause of the > null. When I fixed it, the results of even the simplest queries are still > nulls. > > The code is not generating errors though, it is not generating the proper > results ... > > On Tue, Jun 6, 2017 at 9:13 AM, Andy Seaborne <[email protected]> wrote: > >> >> >> On 06/06/17 00:26, Aya Hamdy wrote: >> >>> Ok. That sounds reasonable so I will work on breaking down my chain of >>> thought into smaller pieces. Thank you so much. >>> >>> I saw an example online where the query syntax is written as a string on >>> Jena. so my query now looks like this: >>> >> >> Use >> >> String.join("\n" >> , "PREFIX rdf:<http://www.w3.org/1999/02/22-rdf-syntax-ns#>" >> , "PREFIX rdf:<http://www.w3.org/1999/02/22-rdf-syntax-ns#>" >> , "INSERT {", >> ... >> , "}" >> ); >> >> then you will have newlines in the string and parser errors will have >> line+column numbers that are useful. >> >> Andy >> >> >> >>> String queryString= >>> "PREFIX rdf:<http://www.w3.org/1999/02/22-rdf-syntax-ns#>"+ >>> "PREFIX cv:< >>> http://www.semanticweb.org/toshiba/ontologies/2017/3/untitle >>> d-ontology-6#>"+ >>> "insert {"+ >>> " ?ass cv:recorded_speed ?avg"+ >>> "}"+ >>> "WHERE {"+ >>> "SELECT (AVG(?speed) AS ?avg) "+ >>> "where{"+ >>> " ?v rdf:type cv:Vehicle ;"+ >>> "cv:vehicleSpeed ?speed;"+ >>> " cv:Vehicle_Road ?r;"+ >>> "{"+ >>> >>> "SELECT ?r"+ >>> "where{"+ >>> >>> "?ass rdf:type cv:Avg_Speed_Sensor;"+ >>> " cv:avgSpeedSensor_Infrastructure ?r"+ >>> "}"+ >>> "}"+ >>> >>> >>> >>> "}"+"GROUP By ?ass ?avg ?r"+ >>> "}"; >>> >>> Then, also based on my research, I feed the query string into the parser >>> and output the model. >>> UpdateAction.parseExecute( queryString, ontologyModel ); >>> ontologyModel.write( System.out, "TTL" ); >>> I encountered many errors but managed to get rid of them all. However, >>> based on the output, nothing has changed. speedSensor1 and >>> speedSensor2 do >>> not have the recorded_speed property added. >>> >>> Of course, I tried debugging, but I could not get any understanding of >>> the >>> problem. >>> >>> >>> I tried breaking the query down to smaller bits right down to doing a >>> simple select on vehicles: >>> >>> String query1= >>> "PREFIX rdf:<http://www.w3.org/1999/02/22-rdf-syntax-ns#>"+ >>> "PREFIX cv:< >>> http://www.semanticweb.org/toshiba/ontologies/2017/3/untitle >>> d-ontology-6#>"+ >>> >>> "Select ?v"+ >>> "where {"+ >>> "?v cv:vehicleSpeed ?speed."+ >>> "}"; >>> >>> Query query = QueryFactory.create(query1); >>> QueryExecution qexec= QueryExecutionFactory.create(query, >>> ontologyModel); >>> try{ >>> ResultSet results=qexec.execSelect(); >>> while(results.hasNext()){ >>> QuerySolution soln=results.nextSolution(); >>> org.apache.jena.rdf.model.Literal name = soln.getLiteral("x"); >>> System.out.println(name); >>> } >>> }finally{ >>> qexec.close(); >>> } >>> But everything I have tried yields in the result "null". >>> >>> Can you give me pointers on how I should go about trying to figure out >>> the >>> problem with the insert function? >>> Sorry if my questions are too naive, but I am trying to grasp the >>> concepts >>> as much as possible. >>> >>> Best Regards, >>> Aya >>> >>> >>> >>> >>> On Mon, Jun 5, 2017 at 8:32 PM, Andy Seaborne <[email protected]> wrote: >>> >>> Then find the sensor of interest, and all cars on that given road. >>>> >>>> GROUP BY the speed sensor, and the AVG is that of calls on that given >>>> road. >>>> >>>> The way to develop complex queris is to write simple parts, then combine >>>> them. >>>> >>>> Andy >>>> >>>> >>>> On 05/06/17 16:46, Aya Hamdy wrote: >>>> >>>> The goal is not to calculate the avg speed of a car. It is rather to >>>>> compute the avg speed of all the cars on a given road and assign that >>>>> computed average as the reading of the average speed sensot attached to >>>>> that road. >>>>> >>>>> Sorry if my wording is causing confusion. >>>>> >>>>> On Jun 5, 2017 5:12 PM, "Lorenz Buehmann" < >>>>> [email protected]> wrote: >>>>> >>>>> No, why do you think so? ?v is the variable that gets assigned a >>>>> vehicle >>>>> >>>>>> for which you compute the avg speed. >>>>>> >>>>>> <Instance> should be ?v, i.e. you have to group by it and select it >>>>>> >>>>>> INSERT { >>>>>> >>>>>> ?v :avgSpeed ?avg >>>>>> >>>>>> } WHERE { >>>>>> >>>>>> SELECT ?v (AVG(?speed) AS ?avg) { >>>>>> >>>>>> .... >>>>>> >>>>>> } GROUP BY ?v >>>>>> >>>>>> } >>>>>> >>>>>> >>>>>> On 05.06.2017 17:03, Aya Hamdy wrote: >>>>>> >>>>>> Hello, >>>>>>> >>>>>>> I will try to explain with examples. I have generated my ontology >>>>>>> from >>>>>>> Protege and converted it to turtle syntax via an online tool. >>>>>>> >>>>>>> *I have a class for average speed sensors:* >>>>>>> >>>>>>> ### >>>>>>> http://www.semanticweb.org/toshiba/ontologies/2017/3/ >>>>>>> >>>>>>> untitled-ontology-6#Avg_Speed_Sensor >>>>>> >>>>>> >>>>>>> untitled-ontology-6:Avg_Speed_Sensor rdf:type owl:Class ; >>>>>>> >>>>>>> rdfs:subClassOf >>>>>>> untitled-ontology-6:Sensor , >>>>>>> >>>>>>> untitled-ontology-6:Speed_Sensor . >>>>>>> >>>>>>> *and a class for vehicles:* >>>>>>> ### >>>>>>> http://www.semanticweb.org/toshiba/ontologies/2017/3/ >>>>>>> >>>>>>> untitled-ontology-6#Vehicle >>>>>> >>>>>> >>>>>>> untitled-ontology-6:Vehicle rdf:type owl:Class . >>>>>>> >>>>>>> *The vehicle class has a property called vehicleSpeed:* >>>>>>> ### >>>>>>> http://www.semanticweb.org/toshiba/ontologies/2017/3/ >>>>>>> >>>>>>> untitled-ontology-6#vehicleSpeed >>>>>> >>>>>> >>>>>>> untitled-ontology-6:vehicleSpeed rdf:type owl:DatatypeProperty ; >>>>>>> >>>>>>> rdfs:domain >>>>>>> untitled-ontology-6:Vehicle >>>>>>> >>>>>>> ; >>>>>> >>>>>> >>>>>>> rdfs:range xsd:integer . >>>>>>> >>>>>>> *The avg speed sensor class has a property called recorded_speed:* >>>>>>> >>>>>>> ### >>>>>>> http://www.semanticweb.org/toshiba/ontologies/2017/3/ >>>>>>> >>>>>>> untitled-ontology-6#recorded_speed >>>>>> >>>>>> >>>>>>> untitled-ontology-6:recorded_speed rdf:type owl:DatatypeProperty ; >>>>>>> >>>>>>> rdfs:domain >>>>>>> >>>>>>> untitled-ontology-6:Sensor , >>>>>> >>>>>> >>>>>>> untitled-ontology-6:Speed_Sensor ; >>>>>>> >>>>>>> rdfs:range xsd:integer . >>>>>>> >>>>>>> The recorded speed by the avg speed sensor allocated to a specific >>>>>>> road >>>>>>> >>>>>>> is >>>>>> >>>>>> the average of the vehicleSpeeds of the vehicles on that specific >>>>>>> road, >>>>>>> where the avg speed sensor class has a property called >>>>>>> avgSpeedSensor_Infrastructure and the vehicle has a property called >>>>>>> Vehicle_Road. >>>>>>> >>>>>>> I have two vehicle instances: Vehicle1 and Vehicle2; and two sensor >>>>>>> instances: SpeedSensor1 and SpeedSensor2. >>>>>>> >>>>>>> Is it clearer now or just confusing? >>>>>>> >>>>>>> so I am guessing following your guide it would be something like: >>>>>>> >>>>>>> INSERT { >>>>>>> <instance> :avgSpeed ?avg >>>>>>> } >>>>>>> WHERE { >>>>>>> SELECT (AVG(?speed) AS ?avg) { >>>>>>> ?v rdf:type :Vehicle ; >>>>>>> :vehicleSpeed ?speed; >>>>>>> : Vehicle_Road ?r; >>>>>>> ?avs rdf:type :Avg_Speed_Sensor; >>>>>>> :avgSpeedSensor_Infrastructure ?r >>>>>>> >>>>>>> } >>>>>>> } >>>>>>> >>>>>>> But the value of the <instance> should come from reading the file, >>>>>>> >>>>>>> right? >>>>>> >>>>>> >>>>>>> >>>>>>> On Sun, Jun 4, 2017 at 9:04 PM, Andy Seaborne <[email protected]> >>>>>>> wrote: >>>>>>> >>>>>>> >>>>>>> On 04/06/17 18:47, Aya Hamdy wrote: >>>>>>>> >>>>>>>> Hello, >>>>>>>> >>>>>>>>> >>>>>>>>> I wanted to add a property called avgSpeed to an instance of a >>>>>>>>> class >>>>>>>>> called >>>>>>>>> FlowSensor. This property should be the average of the values of >>>>>>>>> the >>>>>>>>> property vehicleSpeed attached to instances of the class Vehicle. >>>>>>>>> >>>>>>>>> I read that SPARQL update allows doing this. However, I cannot >>>>>>>>> reach >>>>>>>>> >>>>>>>>> the >>>>>>>> >>>>>>> >>>>>> syntax for doing the* averaging of values* or for building the *SPARQL >>>>>>> >>>>>>>> Update *query using jena with eclipse on the jena website. >>>>>>>>> >>>>>>>>> If Jena indeed supports doing what I intend to do then can someone >>>>>>>>> >>>>>>>>> point >>>>>>>> >>>>>>> >>>>>> out some sources to guide me in my attempt? >>>>>>> >>>>>>>> >>>>>>>>> Best Regards, >>>>>>>>> Aya >>>>>>>>> >>>>>>>>> >>>>>>>>> Calculate the average in a nested select so somethign like (you'll >>>>>>>>> >>>>>>>> have >>>>>>>> >>>>>>>> to >>>>>>> >>>>>> >>>>>> fix this up): >>>>>>> >>>>>>>> >>>>>>>> INSERT { >>>>>>>> <instance> :avgSpeed ?avg >>>>>>>> } >>>>>>>> WHERE { >>>>>>>> SELECT (AVG(?speed) AS ?avg) { >>>>>>>> ?v rdf:type :Vehicle ; >>>>>>>> :vehicleSpeed ?speed >>>>>>>> } >>>>>>>> } >>>>>>>> >>>>>>>> By the way - it is better to more concrete in your description - >>>>>>>> actual >>>>>>>> data for example. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>> >>>>>> >>>>> >>> >
