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Re: proposals for Lists and Seq (ISSUE-77)

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Fri, 21 Oct 2011 11:10:54 +0100
Message-ID: <4EA1452E.7090806@epimorphics.com>
To: public-rdf-wg@w3.org


On 20/10/11 14:39, Sandro Hawke wrote:
> On Thu, 2011-10-20 at 14:58 +0200, Dan Brickley wrote:
>> On 20 October 2011 14:47, Sandro Hawke<sandro@w3.org>  wrote:
>>> On Thu, 2011-10-20 at 13:21 +0200, Dan Brickley wrote:
>>>> On 20 October 2011 13:13, Steve Harris<steve.harris@garlik.com>  wrote:
>>>>> I wouldn't be comfortable with marking Seq as "archaic" or similar unless there's a viable alternative, and I don't think List counts.
>>>>
>>>> Me neither.  Nor "quaint", "twee", "retro" or "regrettable". It's just
>>>> what it is, with no great mystery or confusion.
>>>
>>> Actually, there's a great deal of confusion.  Please do explain -- in
>>> one sentence for newbies -- why we have both Seq and List, and with Seq
>>> better supported in RDF/XML and List better supported in Turtle, and how
>>> someone should decide which to use.
>>
>> Sure - good idea.
>>
>> "The first RDF/XML specifications used a class rdf:Seq with numbered
>> relationships to describe ordered lists; however when the later OWL WG
>> were arm-twisted by W3C staff into using RDF as the syntax to define
>> their language, they persuaded the RDF Core group (and others, e.g.
>> N3/Turtle) to adopt a new list mechanism that used a linked list style
>> that made it easier to tell when a list description was incomplete, at
>> the cost of extra triples."
>
> Nice :-) but you didn't answer the second-half of the question.
>
> Also, why didn't you (the 2001-2004 RDF Core WG) just add an end-marker,
> if that was the objective?     I missed that particular debate.
>
>>> (To put it differently, I think it's quite harmful to the RDF to not deprecate Seq.)
>>
>> I guess you're not paying by the triple for storage?
>
> I should hope that no one stores well-formed lists as triples.

Unfortunately, that isn't how it is.  The reasons are:

1/ The store has to support the triples view anyway because those 
triples really are there (count).

2/ ... and so applications access Seqs/lists as triples (ugly though it 
may be) so the change isn't that helpful.

3/ Handling variable length data items is harder than fixed length ones 
(c.f. arrays in SQL:2008).

4/ There needs to be list-values variables in query to work with them.

	Andy

> Can you think of any way we could merge Seq and List?   Have well-formed
> sequences and well-formed lists both mappable to native lists?   That
> would work fine, except for round-tripping....
>
>     -- Sandro
>
>> cheers,
>>
>> Dan
>>
>
>
>
Received on Friday, 21 October 2011 10:11:33 GMT

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