Arthur; There are a couple of ways to do this. The first is through
SELECT aggregates. Since aggregates are post-result set processing,
you have to use a sub-select. For example, the following will create
property that counts the number of children in the example
kennedysSPIN model.
CONSTRUCT { ?this :numberOfChildren ?n . }
WHERE {
{ SELECT ?this (COUNT(?child) AS ?n)
WHERE {
?this kennedys:child ?child .
} GROUP BY ?this
} .
}
Another approach is to use smf:countMatches, but is only applicable if
a single triple pattern is specified (the aggregate will work with
more complex queries):
CONSTRUCT
{ ?this :numberOfChildren ?n .
}
WHERE
{ ?this kennedys:child ?child .
LET (?n := smf:countMatches(?this, kennedys:child, ?x)) .
}
-- Scott
On Dec 14, 3:35 pm, Arthur Keen <[email protected]> wrote:
> I am looking for an example of how to do aggregation using SPIN. I need to
> aggregate metrics in a part-whole hierarchy and would like to use SPIN rules
> to do it. I have the aggregations working with SELECT, but have not found
> any examples that use CONSTRUCT, so that I can encode the aggregations as
> SPIN rules.
>
> Thanks
> Arthur
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