Re: How to publish SPARQL endpoint limits/metadata?

On 9-10-2013 13:20, Kingsley Idehen wrote:
> On 10/9/13 5:45 AM, Frans Knibbe | Geodan wrote:
>> Hello,
>>
>> If it has really been established that there is no standardized way 
>> to make these things like service limitations known I think it would 
>> be a nice idea to try to initiate a community project.
>>
>> Below are some things that I think would benefit communication 
>> between SPARQL endpoints and user agents. Please know that I am a 
>> novice in Linked Data, so perhaps some of these are already covered 
>> by existing standards or best practices, or do not make sense.
>>
>>  1. The maximum number of results per request (hard limit)
>>  2. The amount of remaining requests (This could be used for a
>>     throttling mechanism that allows only a certain amount of request
>>     per unit of time and IP address. I remember having talked to a
>>     data service on the web where this information was put in the
>>     HTTP response headers)
>>  3. The time period of the next scheduled downtime
>>  4. The version(s) of the protocol that are supported
>>  5. (the URI of) a document that contains a human readable SLA or
>>     fair use policy for the service
>>  6. URIs of mirrors
>>
>> Regards,
>> Frans
>>
>
> Plus:
>
> 7. query timeout (in milliseconds)  -- which determines how much 
> processing time threshold per query .
>
> Ideally, you want to use a combination of timeouts, result size (max. 
> results per query), offet, and limit to enable paging through data .
Yes, enabling paging is the main thing I was thinking about. For that to 
work, one needs to know the maximum page size allowed. SPARQL ORDER BY, 
OFFSET and LIMIT  can be used to build requests for pages. But how does 
the query timeout setting of the server come in to play? I assume that 
if a request for a page of data times out you would get a timeout error 
code (522 probably). What would be gained with prior knowledge of the 
timeout setting?

Regards,
Frans

>
> Kingsley
>>
>>
>> On 8-10-2013 17:45, Leigh Dodds wrote:
>>> Hi,
>>>
>>> As others have suggested, extending service descriptions would be the
>>> best way to do this. This might make a nice little community project.
>>>
>>> It would be useful to itemise a list of the type of limits that might
>>> be faced, then look at how best to model them.
>>>
>>> Perhaps something we could do on the list?
>>>
>>> Cheers,
>>>
>>> L.
>>>
>>>
>>>
>>> On Tue, Oct 8, 2013 at 10:46 AM, Frans Knibbe | Geodan
>>> <frans.knibbe@geodan.nl>  wrote:
>>>> Hello,
>>>>
>>>> I am experimenting with running SPARQL endpoints and I notice the need to
>>>> impose some limits to prevent overloading/abuse. The easiest and I believe
>>>> fairly common way to do that is to LIMIT the number of results that the
>>>> endpoint will return for a single query.
>>>>
>>>> I now wonder how I can publish the fact that my SPARQL endpoint has a LIMIT
>>>> and that is has a certain value.
>>>>
>>>> I have read the thread Public SPARQL endpoints:managing (mis)-use and
>>>> communicating limits to users, but that seemed to be about how to
>>>> communicate limits during querying. I would like to know if there is a way
>>>> to communicate limits before querying is started.
>>>>
>>>> It seems to me that a logical place to publish a limit would be in the
>>>> metadata of the SPARQL endpoint. Those metadata could contain all limits
>>>> imposed on the endpoint, and perhaps other things like a SLA or a
>>>> maintenance schedule... data that could help in the proper use of the
>>>> endpoint by both software agents and human users.
>>>>
>>>> So perhaps my enquiry really is about a standard for publishing SPARQL
>>>> endpoint metadata, and how to access them.
>>>>
>>>> Greetings,
>>>> Frans
>>>>
>>>>
>>>> --------------------------------------
>>>> Geodan
>>>> President Kennedylaan 1
>>>> 1079 MB Amsterdam (NL)
>>>>
>>>> T +31 (0)20 - 5711 347
>>>> Efrans.knibbe@geodan.nl
>>>> www.geodan.nl  | disclaimer
>>>> --------------------------------------
>>
>>
>> -- 
>> --------------------------------------
>> *Geodan*
>> President Kennedylaan 1
>> 1079 MB Amsterdam (NL)
>>
>> T +31 (0)20 - 5711 347
>> E frans.knibbe@geodan.nl
>> www.geodan.nl <http://www.geodan.nl> | disclaimer 
>> <http://www.geodan.nl/disclaimer>
>> --------------------------------------
>
>
> -- 
>
> Regards,
>
> Kingsley Idehen	
> Founder & CEO
> OpenLink Software
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