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Re: Why does rdf-sparql-protocol say to return 500 when refusing a query?

From: Hugh Glaser <hg@ecs.soton.ac.uk>
Date: Sun, 17 Apr 2011 20:07:13 +0000
To: "alexander.dutton@oucs.ox.ac.uk" <alexander.dutton@oucs.ox.ac.uk>, "public-lod@w3.org" <public-lod@w3.org>
Message-ID: <EMEW3|5d76790c0f2b39747f19db4cba2a5b13n3GL7h02hg|ecs.soton.ac.uk|1AAEEAE8-6707-40C0-87E7-5D031820A147@ecs.soton.ac.uk>
Ah, thanks.
That explains it.
I was puzzled why I was getting 500.
I assumed the endpoint was returning 500 by mistake.
Never crossed my mind it might be the the "correct" thing to do.
As a consumer I would like to be able to distinguish a refusal to answer from a failure of the web server to access the store, for example.

----- Reply message -----
From: "Alexander Dutton" <alexander.dutton@oucs.ox.ac.uk>
To: "public-lod" <public-lod@w3.org>
Subject: Why does rdf-sparql-protocol say to return 500 when refusing a query?
Date: Sun, Apr 17, 2011 06:04

Hash: SHA1

Hi all,

The SPARQL Protocol for RDF specification¹ say sin §2.2 that
"QueryRequestRefused [is] bound to HTTP status code 500 Internal
Server Error", and should be used "when a client submits a request
that the service refuses to process". The HTTP 1.1 specification²
states that a status code of 500 means that "the server encountered an
unexpected condition which prevented it from fulfilling the request".

A server might reasonably expect that it will receive
resource-intensive requests, and respond to those by declining to
fulfil them. It is not a client error, not a server error, as the
client is being overly demanding. As such, a 500 response seems — to
me, at least — inappropriate.

The SPARQL protocol spec also says in §2.1.4 that "the
|QueryRequestRefused| fault message [does not] constrain a conformant
SPARQL service
from returning other HTTP status codes or HTTP headers as appropriate
given the semantics of HTTP". Does this contradict §2.2, and the WSDL

I've heard a rumour that one or more implementations return a 509. To
me, a 403 seems somewhat appropriate (but isn't perfect). What do
other people think, and what is currently implemented?



¹ <http://www.w3.org/TR/rdf-sparql-protocol/>
² <http://tools.ietf.org/html/rfc2616#page-70>
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Received on Sunday, 17 April 2011 20:08:09 UTC

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