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Re: Blank Node Identifiers and RDF Dataset Normalization

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Tue, 26 Feb 2013 17:46:13 +0000
Message-ID: <512CF4E5.5030302@epimorphics.com>
To: public-rdf-wg@w3.org


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

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

>
>
>
Received on Tuesday, 26 February 2013 17:46:49 GMT

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