Re: Public SPARQL endpoints:managing (mis)-use and communicating limits to users.

On 4/19/13 9:25 AM, Rob Warren wrote:
>> Hi Rob,
>>
>> There is a fundamental problem with HTTP status codes.
>> Lets say a user submits a complex but small sparql request.
>>
>> My server sees the syntax is good and starts to reply in good faith.
>> This means the server starts the http response and sends an 200 OK
>> Some results are being send....
>> However, during the evaluation the server gets an exception.
>> What to do? I can't change the status code anymore...
>
> Is this really so? Failures in large transfers are common and there 
> are a few ways to detect it from the client's end (wrong format, wrong 
> Content-Length and dropped connection).
>
> There are SPARQL server implementation specifics here, but it's 
> possible to have a good statistical estimate of whether the query 
> runtime or expected transfer amount will exceed the limits before 
> firing the query. Since the query planner has to do this processing 
> before returning triples, you can decide to fire the query or just 
> refuse the request with an error header based on your limits.
>
> If your estimation is wrong and you have to kill the query at runtime, 
> you can re-tune the query planner / optimizer statistics to be more 
> conservative at the next request.
>
> rhw
>
>
>
>
+1


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