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Schema comments

From: Graham Klyne <GK@NineByNine.org>
Date: Tue, 30 Apr 2002 20:43:59 +0100
Message-Id: <5.1.0.14.2.20020430201129.032ffe50@joy.songbird.com>
To: RDF core WG <w3c-rdfcore-wg@w3.org>
I've been looking through the schema draft, but am out of time before I 
could finish.  Here's what I have:

Overall structure
-----------------

This is generally fine, but I found a couple of section headings confusing, 
and think there might be a couple more useful bits of introductory material.

Currently, we have:

Introduction
Example
RDF Schema
Domain and Range Vocabulary
RDF Schema Overview
...

I'd like to see the 3rd para of "RDF Schema" in a section headed RDF 
Classes, and the section "Domain and Range Vocabulary" named something like 
"Application use of RTDF Schema".


Introductory material
---------------------

I also think there's some ideas that could usefully be spelled out in the 
introductory section "RDF Schema", along the lines of:
[[
The basic RDF model uses Resources and Properties to construct assertions 
[ref model theory].  RDF Schema introduces the idea of a RDF Class, and a 
vocabulary for describing certain aspects of RDF Properties and Classes.

Because RDF Schema uses the RDF information model and RDF language, 
applications may define their own vocabularies to augment RDF schema 
descriptions of properties and classes.  (For example, CC/PP uses RDF 
properties to describe attributes of a client device.  It has been 
suggested that CC/PP might define some additional properties that apply to 
such properties to indicate how certain kinds of conflict are resaolved by 
CC/PP:  such properties might reasonably be viewed as an extension to the 
schema vocabulary.)
]]


Schema as restriction vs schema as additional information
---------------------------------------------------------

[This echoes some comments I've made with respect to the Primer...]

I find the use of the term "restrict" in relation to RDF schema to be 
contrary to my understanding.  Adding RDF schema information doesn't 
specifically restrict the things one can say;  rather, it allows an 
application to deduce further things from what is said.  There is no 
meaningful concept of RDF schema-validity - adding RDF schema statements to 
a graph cannot somehow make that graph invalid (even though they may mean 
that some graphs are not meaningful in terms of the intended interpretation 
of the vocabulary used).

E.g. Paragraph 3 in "Introduction" says "... to restrict the possible 
combinations of classes and relationships, ...".  I think that is wrong.  I 
don't think RDF schema imposes *any* such restrictions on correctly formed 
RDF expressions.

Other similar occurrences:
"Domain and Range vocabulary", 1st para, "...limitations on..."


Section headings
----------------

Adding section numbers would make it easier to make references into the 
document.


Details
-------

"Introduction", para 4:
"... types of relationships ..." is this an unfortunate use of 
"types"?  Suggest deleting "types of".

"Introduction", para 4:
"... allows for a finer grained mixing ...":  finer than what?   I'm not 
sure what this means, so can't really suggest an alternative.

"Introduction", para 5:
typo: "vocabualry"
(Otherwise, I think this para is great, especially with respect to my 
comments above about "restriction".)

"RDF Schema", para 1:
I struggled to grasp the first sentence.  Maybe you meant something like 
"... , which in turn describe application-specific ..."?

"RDF Schema", para 1:
Reference to "core vocabulary":  I think this could be confused with RDF 
core, and would suggest referring to it as "schema vocabulary".

"RDF Schema", para 2:
Typo: "seekback"

"RDF Schema Overview", table of RDF classes:
"The class Resource":  I suggest "The class of all RDF resources".
Do we need to be clear about whether this includes lexical values 
(denotations of literals)?

"RDF Schema Overview", table of RDF classes:
"The concept of Class":  I suggest "The class of RDF resources that 
represent RDF classes".

"RDF Schema Overview", table of RDF classes:
"The concept of a property":  I suggest "The class of RDF resources that 
represent RDF properties".

...
This is as far as I got.

I'm out of time for now - sorry!

#g


-------------------
Graham Klyne
<GK@NineByNine.org>
Received on Tuesday, 30 April 2002 16:11:07 EDT

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