Re: temporal relations

On Thu, Mar 23, 2006 at 11:30:51 +0100, Henry Story wrote:
> <#blue> god:timeslice [ tr:inCalendarClockDataType  
> "2006-03-23T10:00:00Z"^^xsd:dateTime;
>                        god:temperature "22"^^xzd:celsius ],
>                       [ tr:inCalendarClockDataType  
> "2006-03-23T10:00:00Z"^^xsd:dateTime;
>                        god:temperature "12"^^xzd:celsius ];

I had a very similar problem in representing trivial provenance-ish
information (when certain files were parsed, what parse errors there were
etc.) inside my triple store. Currently there is a hack updates a triple like
	foo:graphId :lastUpdated "2006-01-01T01:01:01"^^xsd:dateTime .
when each graph is reread, and always adds a
	foo:graphId :updated "2006-01-01T01:01:01"^^xsd:dateTime .

I'm thinking of replacing this with a SPAQRQL query/rule that can always find
the most recent one, along the lines of

	SELECT ?last
	WHERE { foo:graphId :updated ?last }
	ORDER BY DESC(?last)
	LIMIT 1

The graphs have to be done one-by-one as theres no GROUP BY equivalent in
SPARQL.

- Steve