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Re: Can we afford to offer SPARQL endpoints when we are successful? (Was "linked data hosted somewhere")

From: Kingsley Idehen <kidehen@openlinksw.com>
Date: Wed, 26 Nov 2008 22:51:48 -0500
Message-ID: <492E1954.1090609@openlinksw.com>
To: bio2rdf@googlegroups.com
CC: "public-lod@w3.org" <public-lod@w3.org>

Peter Ansell wrote:
> 2008/11/27 Hugh Glaser <hg@ecs.soton.ac.uk <mailto:hg@ecs.soton.ac.uk>>
>     Prompted by the thread on "linked data hosted somewhere" I would
>     like to ask
>     the above question that has been bothering me for a while.
>     The only reason anyone can afford to offer a SPARQL endpoint is
>     because it
>     doesn't get used too much?
>     As abstract components for studying interaction, performance, etc.:
>     In fact, I often consider the components themselves
>     interchangeable; that
>     is, the first step of the migration to SW technologies for an
>     application is
>     to take an SQL-based back end and simply replace it with a
>     SPARQL/RDF back
>     end and then carry on.
>     However.
>     No serious DB publisher gives direct SQL access to their DB (I think).
>     There are often commercial reasons, of course.
>     But even when there are not (the Open in LOD), there are only
>     search options
>     and possibly download facilities.
>     Even government organisations that have a remit to publish their
>     data don't
>     offer SQL access.
>     Will we not have to do the same?
>     Or perhaps there is a subset of SPARQL that I could offer that
>     will allow me
>     to offer a "safer" service that conforms to other's safer service
>     (so it is
>     well-understood?
>     Is this defined, or is anyone working on it?
>     And I am not referring to any particular software - it seems to me
>     that this
>     is something that LODers need to worry about.
>     We aim to take over the world; and if SPARQL endpoints are part of
>     that
>     (maybe they aren't - just resolvable URIs?), then we should make
>     damn sure
>     that we think they can be delivered.
>     My answer to my subject question?
>     No, not as it stands. And we need to have a story to replace it.
>     Best
>     Hugh
> I don't think we can afford to offer the actual public grade 
> infrastructure for free unless there is corporate backing for 
> particular endpoints. However, we can still tentatively roll out 
> SPARQL endpoints and resolvers in mirror configurations together with 
> software which can round robin across the endpoints to get information 
> without overloading a particular endpoint to at least get some 
> redundancy and figure out what needs to be done to fine tune the 
> methods for distributed queries. Once you have the ability to round 
> robin across sparql endpoints and still choose them intelligently 
> based on a knowledge of what is inside each one you can distribute the 
> source RDF to anyone and have them give back the information about how 
> to access the endpoint, and if people are found to be overloading an 
> endpoint send them a polite message to either round robin across the 
> available endpoints or get their own local SPARQL installation which 
> can be configured to respond to work the same as the public endpoint.
> An example implementation of this functionality is the distribution of 
> queries across endpoints for Bio2RDF [1] which together with the 
> distribution of a combination of Virtuoso DB files [2] and source 
> NTriples files [3] make it relatively simple for people to download 
> the software [4], and the resolver package and redirect the 
> configuration file to their own local versions for large scale private 
> use of semantics using exactly the same URI's that resolve using a 
> combination of the publically available resolvers which may or may not 
> be contacting public SPARQL endpoints. An example of a public resolver 
> contacting a combination of public and private SPARQL endpoints is 
> [5]. (Please don't go and overload it though because as Hugh says, the 
> threat of overloading is quite real for any particular endpoint :) ).

If you configure the Virtuoso INI file appropriately the deliberate or 
inadvertent DOS vulnerability is alleviated.

You can append this to your Virtuoso INI (if not there already):

ResultSetMaxRows           = 1000
DefaultGraph               = http://bio2rdf.org
MaxQueryExecutionTime      = 60  ; seconds
MaxQueryCostEstimationTime = 400 ; seconds
DefaultQuery               = select distinct ?Concept where {[] a ?Concept}

> I do agree that arbitrary SPARQL queries should be localised to 
> private installations, but before you do that you have to provide easy 
> ways for people to get private installations which resolve URI's in 
> the same way that they are in the public web.
We have also made this part of the DBpedia on EC2 solution, thus, the 
URIs are localized while retaining original data source links by 
attribution etc.
So <http://<ec2-cname>/resource/Berlin> will be resolved locally will 
using an attribution link (dc:source) to 
<http://dbpedia.org/resource/Berlin> . The attribution triple doesn't 
exist in the quad store (so it doesn't result in one for each resource 
thereby increasing size unnecessarily), we simply produce it "on the 
fly" via a re-write rule.


> Cheers,
> Peter
> [1] http://bio2rdf.mquter.qut.edu.au/admin/configuration/rdfxml
> [2] http://quebec.bio2rdf.org/download/virtuoso/indexed/
> [3] http://quebec.bio2rdf.org/download/n3/
> [4] http://sourceforge.net/project/platformdownload.php?group_id=142631
> [5] http://bio2rdf.mquter.qut.edu.au/
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Kingsley Idehen	      Weblog: http://www.openlinksw.com/blog/~kidehen
President & CEO 
OpenLink Software     Web: http://www.openlinksw.com
Received on Thursday, 27 November 2008 03:52:32 UTC

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