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/untitled-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/untitled-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 <a...@apache.org> 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" <
buehm...@informatik.uni-leipzig.de> 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 <a...@apache.org> 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.
