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Re: Massimo's remarks

From: Eric J. Miller <emiller@oclc.org>
Date: Wed, 25 Nov 1998 14:43:10 -0500
Message-Id: <365C5DCD.C33D70A@oclc.org>
To: massimo@w3.org, www-rdf-comments@w3.org
Massimo,

Thank you for your detailed comments regarding the RDF Model and Syntax
specification.  The following is a response to issues raised in your
attached
message.

Issue 1. I think the BNF as it is is wrong. The problem is a systematic
lack of proper spacings.

We feel that the intent of the BNF is clear to the human reader.  It
is not the purpose of the BNF to be run through a parser generator.
The (prose) statement that RDF is XML by implication makes all the
whitespace rules as specified by XML.

Issue 2. The optional RDF:rdf tag issue:

You are correct.  The error in production 6.1 has been corrected.

Issue 3. RDF allows tags to be used [in two forms] A word of warning
that simultaneous use of these two forms within the same document can
be dangerous for compatibility with SGML processors can be useful.

This is a generic XML issue and does not seem appropriate for specific
mention in the RDF specification.

Issue 4. The Bag container: as it is now, its model representation is
probably too specific;

The Working Group is divided on the question of whether repeated
properties (multiple statements with the same source and predicate but
different objects) should be encouraged with an RDF model.  In any
case, an implementation trying to evaluate equivalence in Bags needs
to enumerate all the members and having two varieties of property
names for collection membership does not simplify that task.

Sincerely,

Ralph Swick, W3C Metadata Activity Leader
Eric Miller, Bob Schloss, RDF Model and Syntax Chairs


> Date: Fri, 23 Oct 1998 18:16:17 -0400
> Message-Id: <199810232216.SAA20979@umpah.w3.org>
> From: Massimo Marchiori <massimo@w3.org>
> To: swick@w3.org
> CC: www-rdf-comments@w3.org
> Subject: Massimo's remarks
>
> Hi Ralph,
> I had a last read of the spec this week (last call helps to
push....;-)
> BTW, compliments for the latest spec, it is really a great improvement

> over the past.
> Just few technical comments, hope they are useful:
>
> 1) I think the BNF as it is is wrong. The problem is a systematic
> lack of proper spacings. For example, [2] would give
> <rdf:DescriptionID=....> since you have no space after the
> "<rdf:Description" part. This is systematic and occurs everywhere in
> these situations. The easy solution is just to add a space before
> every attribute (eg, in [5] having ' ID="' in place of 'ID="').
> 2) The optional RDF:rdf tag issue:
>  a) as it is now (in [1]) it is wrong: unfortunately optional tags
>     can't be expressed this way in BNF. The point is that
>     RDF ::= ['<rdf:RDF>'] description* ['</rdf:RDF>']
>     can give things like
>     '<rdf:RDF>' description*
>     or
>     description* '</rdf:RDF>'
>     The proper way is to split the cases in advance, eg with something

>     like:
>     RDF ::= description* | ('<rdf:RDF>' description* '</rdf:RDF>')
>  b) In any case, the optional tag is not reflected in the final
>     RDF formal grammar ([6.1]), where the RDF:rdf tag is mandatory.
>  c) just a warning that omitting the RDF tag can lead to non
>     well-formed XML can be useful
> 3) RDF allows tags to be used both in compact form (self-closed, like
>    <rdf:Description .... />), or more generally in long form as in
>    <rdf:Description...> .... </rdf:Description>
>    A word of warning that simultaneous use of these two forms within
>    the same document can be dangerous for compatibility with SGML
>    processors can be useful.
> 4) The Bag container: as it is now, its model representation is
>    probably too specific; now, a bag with {Joe, Ann, Mary} has a
>    different model representation than {Ann, Joe, Mary}. This forces
>    you to put much more effort in the model equivalence, or in other
>    words, makes the model representation unnecessarily fine-grained.
>    The point is the use of RDF:_1 RDF:_2 etc. I agree this way is
>    consistent with Alt and Seq, but, here we're talking about a
>    different data structure, where the order doesn't matter. So,
>    it would be probably better to encode this in the model
>    using just a unique rdf:_bag (for example) predicate. This is
>    a simple edit to do, and gives you the important property that
>    a Bag has one model representation and not many different ones,
>    something not true now (and therefore, rather tricky imho...).
>
> Ok, hoping this is of some help, and good luck with the (last! :-)
edits.
>
> Cheers,
> -Massimo
>
> /---------------------------------------------------------------\
> | Massimo Marchiori                    Room NE43-350            |
> | The World Wide Web Consortium (W3C)  545 Technology Square    |
> | MIT Laboratory for Computer Science  Cambridge, MA 02139, USA |
> | WWW: http://w3.org/People/Massimo    Phone: +1 (617) 253 2442 |
> | Email: massimo@w3.org                Fax:   +1 (617) 258 5999 |
> \---------------------------------------------------------------/
>
Received on Wednesday, 25 November 1998 14:43:36 GMT

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