Re: review of LCC documents as of 26 December 2002

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Subject: Re: review of LCC documents as of 26 December 2002 
Date: Tue, 07 Jan 2003 12:40:53 +0000

> >>>"Peter F. Patel-Schneider" said:
> > 
> > Integrated Review of the RDF Core WG LCC Documents (as of 26 December 2002)
> > 
> > 
> > This review is the result of reading the RDF Core WG LCC Documents as they
> > existed on 26 December 2002.  
> 
> <snip/> 
> 
> > RDF/XML Syntax Specification (Revised) Editor's version of W3C Working
> > Draft XX Month YYYY
> > 
> > Section 2: 
> > 
> > It would be better to state up front that this section is non-normative,
> > instead of making it subordinate to sections 6 and 7.  In particular, what
> > happens if section 6 and 7 are silent on some point?  Does this make this
> > section normative? 
> 
> This section has useful examples that are correct rdf/xml as well as
> explaining the ideas that the grammar uses such as node element,
> property element, etc.  If there are specific things 6 & 7 are silent
> on that you need clarifying, please list them.

The point is that I don't know whether there are any missing pieces of
Sections 6 and 7, nor does, I suspect, anyone else.  (There may be a
general consensus that Sections 6 and 7 are exhaustive, but no certainty as
of yet.)  The way the document is now structured, however, means that if
there are any such missing pieces, and if some example is not covered by
Sections 6 and 7, then this example extends the treatment given in Sections
6 and 7.

In general, examples should only be illustrative, and never normative.
First, there are just too many things that can go wrong in an example.
Second, there is no way to cover a non-finite category with examples.

> > Section 5: 
> > 
> > What does it mean for a namespace to contain a set of names?  How is this
> > regulated in RDF?  Can the owner of any namespace close off the namespace?
> > How can this be done in RDF?  Without answers to these questions, saying
> > that the RDF namespace contains only a certain set of names doesn't make
> > sense.
> 
>   [Definition:] An XML namespace is a collection of names, identified
>   by a URI reference [RFC2396]
> 
>   -- http://www.w3.org/TR/1999/REC-xml-names-19990114/
> 
> The RDF namespace given here is just such an XML Namespace - a
> collection of names identified by a URI reference.  Section 5.1 tells
> you what the names are by listing them along with a rule for the
> constructed ones of the _n form and gives you the URI reference.
> 
> The other questions are best directed at what XML namespaces are
> about since the RDF model does not have a concept of namespaces.

If the notion in Section 5.1 is an XML Namespace, then it should correspond
to that notion.  The XML Namespace document is quite vague as to the
contents of a namespace, but I don't see in it anywhere the notion of being
able to enumerate the names in a namespace, nor removing a name from a
namespace.  

> > The container property names are not of the form _n where n is a positive
> > integer, they are of the form _n where n is a  base-10 numeral without
> > leading zeros that represents a positive integer. 
> 
> Not just positive; 0 is forbidden.  How about
>   "where n is a decimal integer greater than zero with no leading zeros"

Well, 0 is generally not considered to be a positive number, just a
non-negative number, but if you think that ``greater than zero'' is better
than ``positive'' go ahead and use that.

> > The statement that other names from the RDF namespace can be used goes
> > against the idea of a closed RDF namespace and also against certain
> > comments from the RDF Core WG.  However, it appears to be much closer to
> > historical truth than these other statements.  

[...]

[I have addressed the treatment of rdf:nodeID and blank nodes in a separate
message.] 

> > Section 8: 

[...]

> > The last sentence of the section is wrong, and, moreover, contradicts the
> > rest of the section. 
> 
> The sentence is not wrong but may be misleading.  Jeremy Carroll, the
> author of the paper proposes changing to:
>   "This describes using the original syntax without the subsequently
>   added rdf:nodeID attribute."
> 
> As far as I know it remains true that all legal RDF graphs (no errors
> or warnings) with blank nodes can be serialized to RDF/XML using
> rdf:nodeID, since anywhere you can use a resource URI (rdf:about or
> rdf:resource) you can now use a blank node identifier.  If you have a
> counter example, I'd be interested to see it.

Well, the very first sentence of Section 8 says that

	There are some RDF Graphs as defined in the RDF Concepts and
	Abstract Syntax Working Draft that cannot be serialized in RDF/XML.

Either this or

	... now allows all graphs with blank nodes to be serialized.

must be wrong, I believe that the former sentence is correct and the latter
phrase is incorrect.


[...]


> Dave


Peter F. Patel-Schneider
Bell Labs Research
Lucent Technologies

Received on Tuesday, 14 January 2003 11:02:06 UTC