Hi. I have been having trouble with a SPIN rule I've constructed to
aggregate a set of values. It seems as if the variable ?*this* is not
being bound properly, and I wonder if this is due to my SPARQL formulation
or to TBC.
Here is the problem. Conceptually, there are counts of a particular
phenomenon occurring on a given day during a given hour: <day, hour,
count>. The rule's task is to sum the counts for each hour, and assign that
sum to the count for the appropriate day. The SPIN rule is defined for a
'Daily' object (representing a day); the counts are assigned to 'Hourly'
objects (representing an hour of a particular day).
I assumed that the aggregation function SUM (in the rule below) would sum
over only the counts for a single day, because I constrained the variable
?day using ?*this*. However, the results indicate that the day was not
constrained because the sum for each day is the same: the grand total of
all counts over all days. Perhaps I do not understand the scoping rules for
?*this* within the SPARQL expression.
Any guidance would be appreciated! When I execute the SELECT clause alone
in the SPARQL Query Editor, substituting a specific 'Daily' instance for ?
*this*, I do get the desired sum for the hours in that day.
Thanks,
Rich
:Daily a owl:Class ;
spin:rule
"CONSTRUCT {
?this :xcount ?dailyCount .
}
WHERE {
{
SELECT ((SUM(?hourlyCount)) AS ?dailyCount)
WHERE {
?this :xday ?day . #Should bind ?day to the :xday value
for the specific instance over which the rule is firing
?hourly :day ?day .
?hourly :count ?hourlyCount .
}
} .
}"
:D1 a :Daily;
:xday 1 .
:D2 a :Daily;
:xday 2 .
:Hourly a owl:Class .
:H1D1 a :Hourly;
:count 10 ;
:hour 1 ;
:day 1 .
:H2D1 a :Hourly;
:count 10 ;
:hour 2 ;
:day 1 .
:H3D1 a :Hourly;
:count 10 ;
:hour 3 ;
:day 1 .
:H1D2 a :Hourly;
:count 10 ;
:hour 1 ;
:day 2 .
:H2D2 a :Hourly;
:count 10 ;
:hour 2 ;
:day 2 .
----------------
Inference Result:
:D1 :xcount 50
:D2 :xcount 50
Expected Result:
:D1 :xcount 30
:D2 :xcount 20
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