Date: 2010-05-18 21:39:18
From: J.Kopecky-at-open.ac.uk
Hiya,
we use OWLIM through Sesame and it seems that the function RepositoryConnection.clear(context) clears the whole knowledge base, not only the triples from the given context, as I understand it should. 
Is this (clearing the whole KB) the expected functionality? If so, how can one best remove just all the triples from a given context? Also, will this remove the triples that are implied by the contents of this context?
Thanks,
Jacek

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Date: 2010-05-28 12:07:12
From: ivan.peikov-at-ontotext.com
Hi Peter,
When working heavily with context it helps if the context index is built and 
maintained (this is the build-pcsot parameter in the BigOWLIM configuration).
Do you have such an index in your setup?
Cheers,
Ivan
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Date: 2010-05-19 13:07:03
From: ivan.peikov-at-ontotext.com
Hey!
One possible reason for the described behavior would be that clear() was 
called with some context that OWLIM didn't recognize. In the current 
implementation of BigOWLIM, clearing an unknown context clears the whole 
repository. So beware, until this bug is fixed.
Inferred triples will be automatically removed unless they were inferred by 
other reasons as well.
Cheers,
Ivan
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Date: 2010-05-19 14:38:51
From: a.p.gibson-at-uva.nl
Hi Ivan, Jacek,
I'm glad someone else has found this. I also had this problem when 
experimenting with SwiftOWLIM, where the repository was totally cleared 
when trying to remove a context through the OpenRDF workbench. The 
context I was trying to remove definitely did exist so I think the 
problem may be more than just a bug with clearing an unknown context.
One guess might be the format of the provided context that is being 
cleared. Sesame expects the context to be provided in angle brackets - 
i.e. <context> - perhaps owlim does not expect this and so regards it as 
an unknown context, and therefore clears everything because of the bug?
I use context a lot for maintaining content and can not really start 
using OWLIM until this is working :-( which is a shame as I really could 
use its functionality.
Cheers,
Andrew
-- 
Dr Andrew Gibson
Universiteit van Amsterdam
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Date: 2010-05-28 16:46:29
From: ivan.peikov-at-ontotext.com
Hi Andrew, Jacek,
Indeed, this is verified to be a bug in SwiftOWLIM. It if filed in our bug 
tracker and we hope to address it in the upcoming SwiftOWLIM release.
Cheers,
Ivan
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Date: 2010-06-01 11:38:15
From: peter.kostelnik-at-tuke.sk
hello,
hopefully the last issue in this thread :)
we've got the serious problem with deleting the data from the context
using conn.clear(ctxURI) ..
setup: cca. 100 mil. of statements, hundrets thousands of context graphs
(each containing about hundreds of statements) ..
we are running huge postprocessing, which groups the data into contexts
and regroupes data between the contexts .. each operation requires
deletion of more contexts in each step ..
one context deletion takes a minutes (this time) .. what causes, that
(optimistic) estimation of the processing time is more that one month :)
pls, where can be the problem? .. or what can be the workaround?
thanks,
Peter K.
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Date: 2010-05-21 16:03:10
From: peter.kostelnik-at-tuke.sk
hi there ..
I'd like to ask for the hints, how to configure BigOWLIM for the best
possible performance in run-time ..
there is a couple of parameters which (I believe) can improve the
triple-store performance, so my question is, how to set them to achieve
the best ..
our setup is as follows:
---
approx. number of statements: for sure more than 100 millions (pls, how
affect the copying the same graphs of statements into more different
context? are they copied to as different squads or there is just the kind
of association of same statements to the different context URIs?)
we are about to use the RDFS reasoning, but in most of cases (in this
moment - in all cases) for now we don't use the reasoning at all yet..
right now we don't use the rules
we are firing the SPARQL queries, we are also using the
RepositoryConnection instances to retrieve the data ..
we are running the two different scenarios:
---
scenario 1: off-line load of all data
this is done only once - the very first load of the data into triplestore ..
we are using two instances of Repository, first for loading the data,
second for post-processing ..
first instance is initialized, all data are loaded into the triple-store
in a single transaction commited after the load is finished .. when
loading, the snippets of data are parsed and stored into more separate
contexts ..
after the loading is finished, there comes the huge post-processing .. so
first repository is shutted down, and post-processing repository is
initialized .. it does the work and it is shutted down - data are in
triple-store ..
loaded data are moved to the production system (running as BigOWLIM under 
sesame server) ..
scenario 2: run-time
---
BigOWLIM is accessible remotely using HTTPRepository, handling the lots of
queries and searches ..
pls, do you have some hints, how to squeeze the best from BigOWLIM?
if talking about the RAM, can you, pls - if possible - draw possible
alternatives for several setups (<- just curious what effect has this
parameter (sure, I know - the more the best :) ))?
thanks a lot in advance, cheers,
Peter K.
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Date: 2010-05-27 07:44:13
From: barry.bishop-at-ontotext.com
Hello Peter,
Sorry for the delay in answering your email. We have had a number of
urgent tasks and holidays in the last few days.
Nevertheless, we will discuss your tuning requirements today and come up
with some suggestions.
Thanks for your patience,
barry
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Date: 2010-05-27 12:15:23
From: peter.kostelnik-at-tuke.sk
hi there, barry,
thats ok .. thanks for your support ..
btw, meanwhile, some new stuff arised :) .. there is some time problems
when BigOWLIM deletes the triples from specified context, e.g.
connection.clear(contextURI)
we are doing quite heavy post-processing above cca. 80-100 milions of
statements.. in our case, we are aggregating the snippets of data and
putting them together into specific contexts (to be able to retrieve them
fast) .. and in most cases, we have to replace the data in more contexts
.. logs of the process say, that removing the context data using
connection.clear(ctx) is fatally slow .. in some cases  it takes more that
hour(s) .. please, do you have some idea, how to deal with this?
thanks in advance, cheers,
Peter K.
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