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Re: LC-Comment on POWDER-Semantics

From: Phil Archer <phil@philarcher.org>
Date: Mon, 26 Jan 2009 15:32:15 +0000
Message-ID: <497DD77F.7010303@philarcher.org>
To: Michael Schneider <schneid@fzi.de>
CC: public-powderwg@w3.org, Stasinos Konstantopoulos <konstant@iit.demokritos.gr>

Then I must humbly apologise for our lack of manners.

I'll copy and paste the comments and resolutions from the comments 
tracker below but the revised document [1] is probably the best guide to 
how we incorporated your welcome comments. I have not copied the various 
typos your pointed out- they were all corrected and we were grateful to 
you for spotting them.

Again, sincere apologies for not having sent this to you a long time ago.

Cheers

Phil.

Comment:
Why the "SHOULD" here? From the assumptions stated above (wdrs:issuedBy 
is a subPropertyOf both dcterms:
creator and foaf:maker) it follows logically that this URI denotes an 
instance of both classes.

Resolved Yes

This was a mistake as the intention of allowing either
of the two Agents was wrongly encoded as subsuming issuedby under
both dc:creator and foaf:maker. In the current draft using dc:Agent
or foaf:Agent as filler for issuedby has been reduced to a
suggestion, as issuedby is an owl:AnnotationProperty and cannot
have a range restriction.


Comment: Typo? "this that"

Reply: No, but maybe not expressed in the clearest way
possible. "It is this [new class] that is described..."

This text will be removed from the next draft anyway,
as this feature-at-risk has been dropped. (cf. LC-2126)


Comment:
Typo? Is "refer" meant?

Resolved no.
No, defer is the correct word, in effect the document says "don't look 
at this descriptor set - look at that one over there instead." You can 
replace this one with that one... i.e. defer to it.


Comment:
There is no owl:Property, only rdf:Property.
Further, if you apply RDFS/OWL-Full semantics, then every instance of 
owl:DatatypeProperty is also an instance of
rdf:Property, so the second axiom would be redundant.

Reply: Fixed. Thanks.


Comment:
Although technically possible in OWL Full, I suggest to /not/ build 
custom ontology properties. AFAIK, the set of
ontology properties in OWL is intended to be fixed; at least I don't see 
any encouragement in the OWL documents to
create custom ontology properties. I suggest to make 'attribution' into 
an owl:AnnotationProperty, instead. The creation
of custom annotation properties is ok. It is also ok to add annotation 
properties to instances of the class owl:Ontology.
For example, it is quite common to add an rdfs:comment to an ontology.

Resolved yes.
Formal range restrictions have been removed from the current draft to
ensure that attribution elements are owl:AnnotationProperty instances.

Comment:
I don't follow this argumentation. I don't see that the bNode leads to 
any problems when the descriptor set is defined
independent on any DR.
Maybe there is a misunderstanding in what the above example means. The 
existential variable isn't about resources
from a DR, but about the values of a descriptor for such resources. The 
construct above tells the following: If the
above descriptorset is defined for some DR, and r is a resource in that 
DR (i.e. if r is in the IRI-set defined by that DR),
then there /exists/ some x, being an instance of class Wood, where x has 
a shiny finish and is made of cedar, and the
following relationship holds: 'r ex:material x'. the existential 
variable x appears on the /right/ hand side of the
relationship!
If this was a misunderstanding, then I suggest to simply remove the 
whole paragraph.


Resolved partial:
Paragraph removed as a response to LC-2126,
as the WG has resolved to drop this feature-at-risk.

(Resolution to LC 2126 put restrictions on the semantics that can be 
expressed in a POWDER doc).

Comment:
Why a class? I think that this is a bug. PolishedCedar should probably 
rather be an /instance/ of class Wood. Just
compare this with Example 3-10 and my comment to paragraph following Ex 
3-10. The only difference between
Ex-3-10 and Ex-3-11 is that the latter uses an URI where the former uses 
a bNode. In both cases, an instance of class
ex:Wood is created.
So the correct mapping should be:
1 <owl:Class rdf:nodeID="descriptorset_1">
2   <owl:intersectionOf rdf:parseType="Collection">
3     <owl:Restriction>
4       <owl:onProperty
          rdf:resource="http://example.org/vocab#material"/>
5       <owl:hasValue>
6          <ex:Wood
          rdf:about="http://my.example.org/myVocab#PolishedCedar">
7         <ex:finish rdf:resource="http://example.org/vocab#shiny"/>
8         <ex:madeof>cedar</ex:madeof>
9         </ex:Wood>
10      </owl:hasValue>
11    </owl:Restriction>
12   </owl:intersectionOf>
13 </owl:Class>

Reply:
No, not a bug at all.
The idea here was that a particular piece of PolishedCedar is the
property filler, but the class of PolishedCedar pieces of woord
is not defined in any available vocabulry, so the POWDER doc
has to create the class and instantiate an (otherwise unknown)
particular piece of wood of this class.

Either way, this feature-at-risk has been removed (cf LC-2126)


Comment:
The OWL/XML URI is at risk: There is an ongoing discussion in the OWL WG 
whether there should be a URI for the
XML syntax which is distinct from the OWL namespace. See 
<http://www.w3.org/2007/OWL/tracker/issues/109>

Resolved yes:
This was a mistake, left-over from a previous (unpublished) version.
The relevant section (4.6) was, is fact, already using the owl2
vocabulary (http://www.w3.org/2006/12/owl2#) since the LC draft.
Thanks drawing our attention to this.

Comment:
AFAIK, the URI <http://example.org> is reserved for such examples. And I 
have seen it being used elsewhere in this
document. So I suggest to simply state this URI here instead of the 
given sentence.

Resolved yes
OK, but I think the existing text is clear so I've amended it to say "An 
arbitrary prefix used to denote an 'example vocabulary' from the 
example.org domain."

Comment:
Even though RDF/XML is the preferred RDF serialization used to represent 
RDF data in this document, it is probably
not a good idea to talk about "RDF/XML statements" when referring to 
child elements of 'attribution'. I cannot see any
RDF/XML-specific aspects here. These statements are probably intended to 
show up in every RDF serialization, such
as Turtle. So I suggest to rather talk about "RDF statements".

Resolved partial
This had already been rephrased in response to a comment by
Peter Patel-Schneider (LC-2116), that RDF statements are
not about anything at all.


Comment:
It's misleading to talk about a "union" here, although correct in some 
sense. The statements are combined by "AND". I
suggest to say "conjunction" instead.

Resolved partial:
Misleading as "union" might be, "conjunction" would be outright wrong.
Will be rephrased so as to not use any logic terminology

Comment:
This "all resources specified by" statement is a very informal way to 
"enumerate" the IRIs from the iriset. I guess the
reason is that the iriset can be specified by a regular expression, and 
so a finite enumeration is not always possible,
right? I suggest to say a few words about this, because I assume that 
this sort of notation will confuse people.

Resolved no:
Please note the phrase "the IRI set has been elided for clarity (the 
semantics of the IRI set is discussed in Section 4 below)" immediately
above Ex 3-1. We simply defer showing both POWDER/XML irisets and
their RDF translations for clarity, as these have not yet been
introduced, and informally describe what should be there.

Please let us know if your editorial comment persist after this
explanation and you think that this should be made more explicit
in Ex 3-2, 3-3, and 4-3.


Comment:
A rational for this "MUST NOT" statement should be given. At least under 
RDFS/OWL-Full semantics, RDFS and
OWL classes are RDF(S) resources, too.

resolved yes:
As you note, the restriction is there to maintain OWL-DL
semantics for POWDER documents. A short note to this
effected has been added to the current draft.

Comment:
This is a strange sentence for a spec, and it does not seem to have any 
relevance. I suggest to remove it

Resolved yes:
This is meant to discourage without prohibiting the use of RDFS 
properties as descriptors. Rephrased.


Comment:
In the axiomatic triples, hasIRI is written without a namespace prefix, 
but in the semantic condition below, it is written
with a namespace prefix. Note that in sec. 4.3, matchesregex had also be 
written with the wdrs prefix.

Resolved yes
Thank you for spotting the mistake. Will be fixed in the
next draft.


Comment:
In 4.3, the domain of wdrs:matchesRegex was rdfs:Resource. Now the 
domain of hasIRI is owl:Thing. Although, under
OWL Full semantics, these two classes are equivalent, one should decide 
for one in order to be coherent.

Resolved yes:
Thanks for spotting this, the Sect 4.6 domain is wrong.




[1] http://philarcher.org/powder/formal/formal-20090123-diff.html
Clearly this is a temporary URI but this is the most up to date version 
of the document. Your suggestions are cited in the change log (section 8.2).


Michael Schneider wrote:
>> -----Original Message-----
>> From: Phil Archer [mailto:phil@philarcher.org]
>> Sent: Monday, January 26, 2009 3:03 PM
>> To: Michael Schneider
>> Cc: public-powderwg@w3.org; Stasinos Konstantopoulos
>> Subject: Re: LC-Comment on POWDER-Semantics
>>
>> Michael,
>>
>> I'm just going through and checking that all comments that we have
>> received have been answered. Yours certainly were, in that several
>> changes were made [1] to the Formal Semantics document as a direct
>> result of your comments, for which, I would like to again express the
>> WG's thanks.
>>
>> What I can't find is the e-mail from us (specifically from Stasinos
>> Konstatopoulos) saying "here's how we handled your comments and is this
>> OK with you?"
>>
>> Stas - did you send such an e-mail? Michael - did you get it?
> 
> No, I don't remember having received such an answer.
> 
> Best regards,
> Michael
> 
>> Thanks
>>
>> Phil.
>>
>> [1] http://www.w3.org/TR/2008/WD-powder-formal-20081114/#sincelc
> 
> --
> Dipl.-Inform. Michael Schneider
> Research Scientist, Dept. Information Process Engineering (IPE)
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> Fax  : +49-721-9654-727
> Email: schneid@fzi.de
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> 
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-- 
Phil Archer
w. http://philarcher.org/
Received on Monday, 26 January 2009 15:33:00 GMT

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