Re: Blank Node Identifiers and RDF Dataset Normalization

On Tue, Feb 26, 2013 at 9:46 AM, Andy Seaborne <
andy.seaborne@epimorphics.com> wrote:

>
>
> On 26/02/13 16:36, Kingsley Idehen wrote:
>
>> On 2/26/13 6:53 AM, Steve Harris wrote:
>>
>>> On 2013-02-26, at 11:21, William Waites <wwaites@tardis.ed.ac.uk> wrote:
>>>
>>>  On Tue, 26 Feb 2013 11:10:55 +0000, Steve Harris
>>>> <steve.harris@garlik.com> said:
>>>>
>>>>  Yes, but this can only happen if you merge multiple datasets,
>>>>> right? Otherwise no-one gets to write anything into the "default
>>>>> graph" against the will of the dataset maintainer.
>>>>> This is related to the reason why I find the idea of having a
>>>>> single format that can express both Graphs and Datasets so scary
>>>>> - you can bring this kind of situation on yourself without any
>>>>> prior warning. Very bad idea.
>>>>>
>>>> I agree, but this arises from the existing of a special graph called
>>>> default and the somewhat non-standard use of the word "default". A
>>>> longer but more accurate name might be, the "graph that cannot be
>>>> named or referred to of which there is only one where we put triples
>>>> that we can't think of a better place to put".
>>>>
>>>> This could easily be solved by putting
>>>>
>>>>     default_graph = http://some.name/graph
>>>>
>>>> in your sparqlserver.ini file and then manage the contents of that
>>>> named graph whatever way you see fit.
>>>>
>>>> We do not need the notion of "default graph" in the core RDF specs! It
>>>> is a mistake. Please let us get rid of it.
>>>>
>>> I agree wholeheartedly, and argued quite vociferously against it's
>>> inclusion in SPARQL 1.0, but I think it's too late now. The anonymous
>>> genie is out of the bottle.
>>>
>>> - Steve
>>>
>>>
>> As implementers of SPARQL compliant stores and DBMS engines, we (you,
>> Andy, I and others) do have the ability to conjure up our own best
>> practices which could then cycle back to the next round of RDF and
>> SPARQL specs related revisions. It's happened in the past, so why not
>> handle this matter the same way?
>>
>> Conclusion: We discourage the use of anonymous default graphs in our
>> respective products. Every useful thing should be denoted using an
>> identifier.
>>
>
> Jena users find the default graph concept useful:
>
> 1/ When there is one graph being published
>
> 2/ As the union of the named graphs
>

+Inf


>
> 3/ As a single place to put the manifest
>
> Conclusion: you don't have to use it if you don't want to.
>
> (all well worn points)
>
>         Andy
>
>
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