On 1/10/13 7:44 AM, chris dollin wrote:
On 10 January 2013 12:03, Augusto Herrmann <[email protected]> wrote:Greetings!We're implementing a Linked Data API for the Brazilian federal budget [1], using Elda, in a similar way the UK government has done with some of its open data. It's still in an early alpha stage, though. What we're having difficulty with is defining the Views for the item-de-despesa [2]. In our spec [3], we can's even list all the properties lest the SPARQL query becomes too complex for Virtuoso to handle. Even with only a few properties, if the user chooses to list 25 or more items per page, the query breaks. We've looked at the schools example view [4] and it looks quite similar, but the generated SPARQL query is much simpler. Does any one have a clue on what's wrong with the views we're defining? [1] http://orcamento.dados.gov.br/ [2] http://orcamento.dados.gov.br/doc/item-de-despesa [3] http://dev.dados.gov.br/codigo/outros/orcamento-linked-data/files/305212de5f6852e447ea13bae4afa5cbf47f99b5/specs/orcamento.ttl#L47 [4] http://code.google.com/p/linked-data-api/source/browse/trunk/examples/config/education.data.gov.uk.ttl#35Does Virtuoso implemented nested SELECTS and have you enabled them in your Elda config? Without nested selects, the core of a View query is repeated for every selected item. If the view core is big, the entire query is enormous, and can blow up buffers between Elda and the SPARQL endpoint. "Enormous" meaning multiple megabytes. Which is why Elda has the nested select option ... Chris (Stuart may have some other ideas.)
Add virtuoso list to the cc.Virtuoso supports SPARQL subqueries. I've provided an example here: http://bit.ly/UNaKyA .
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