Re: [Myexperiment-discuss] Upgraded myExperiment SPARQL endpoint

[David R Newman]

Hi George,

When 4Store returns a set of results that it believes may not be
complete it will return a warning message.  As yet I have not
encountered a query where I haven't be able to increase what they
describe as the "soft limit" and get it to return all the results so
there is no longer a warning message.  

I think it is inevitable that any triplestore (or any database come to
that) needs to have some way of handling complex or data heavy queries
so that they don't kill the server.  It does seem that 4Store's solution
is a fair compromise.  I don't currently forsee how it works being a
showstopper but it is something we need to keep and eye on.

Regards

David Newman

On Thu, 2009-11-19 at 11:33 +0000, Jerzy Orlowski wrote:
> Hi David
> 
> Sorry for not replying but I had 150 emails to read...
> 
> The size limit of a query might be a really big blocker in the future. 
> For example imagine a query that returns all links that we want to run 
> for making the statistics. There should be a method to do it in SPARQL
> 
> George
> 
> David R Newman wrote:
> >
> > Hi All,
> >
> > I have been working on upgrading myExperiment’s SPARQL endpoint to use 
> > 4Store (http://www.4store.org) from JENA. This should make it much 
> > quicker at finding results than it has been in the past. I am 
> > currently running a test instance of the 4Store-backed SPARQL endpoint 
> > at http://rdf.myexperiment.org/sparql4. So if people want to try out 
> > some of their more complex SPARQL queries to see if they run quicker 
> > that would be most appreciated.
> >
> > I have endeavoured to maintain all the previous functionality in as 
> > similar way as possible but inevitably there are some differences:
> >
> > - No JSON results format
> >
> > - 4Store does not have a way of timing out queries that take too long. 
> > They either return only partial results and/or send a warning message 
> > about the complexity. Instead of a timeout option I have provided a 
> > “Resource Usage” option. This is defaulted to 5% which is suitable for 
> > most basic queries but if you get a warning saying that a query could 
> > not return all results then increasing this percentage should help.
> >
> > In theory the endpoint should be updated each morning much like the 
> > current endpoint but I have only just sorted out the scripts to do 
> > this and I wouldn’t want to guarantee their reliability at the moment.
> >
> > Anyway, any comments/feedback would be most appreciated.
> >
> > Regards
> >
> > David Newman
> >
> >
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