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Re: First crack at profiles in primer

From: Ivan Herman <ivan@w3.org>
Date: Sat, 12 Apr 2008 12:07:50 +0200
Message-ID: <480089F6.1020000@w3.org>
To: Bijan Parsia <bparsia@cs.man.ac.uk>
CC: OWL Working Group WG <public-owl-wg@w3.org>
Hi Bijan,

I was trying to find a good reason to shoot you, but I did not find 
any:-( Sigh...:-)

Seriously, I find the text really good as a start. Deep bow towards 
Manchester...

I was not sure how you wanted this text to evolve. I first tried to use 
the {{Review}} macro but it seems that the style did not work for this 
(why?) so I was not sure how to do it. I ended up writing all my 
comments in this mail.... I hope that is fine with you.

---- Introduction ----

(I am not sure how to handle that, actually): with this numbering scheme 
we have now, when I use the word 'OWL', do I mean 'OWL in general, both 
OWL 1 or OWL 2', or do I mean OWL 1? I tend to think now in terms of the 
former, but it is not 100% clear what you mean in the text (you 
specifically talk about OWL 1 in the last section). It may be worth 
emphasizing that what you say about Full/DL is valid both for OWL 1 and 
OWL 2, ie that OWL 1 has adopted this fundamental "cut", and OWL 2 has 
adopted it, too.

You say (about OWL Full): "One can still define classes using 
restrictions or constraint properties with property chains, and so on.". 
Why 'still'? As OWL Full is unrestricted, there is no 'still', so to say...

(b.t.w., I do not think that remarks like "(subject to resource 
constraints)" or "(modulo bugs in the implementation)." are necessary, 
mainly if this text end up (as I think it should) as part of an official 
document..., but that is a stylistic issue only...)

----- EL++ -----

I know the role of SNOMED and NCI played for EL++, but I am not sure 
that should be part of such a profile description. First of all, most of 
the people will have no idea what these ontologies are, and, secondly, 
it gives the wrong impression that we define a profile for a particular 
branch of industry.

My reading of EL++ is that some of the property characterization 
([inverse]functional, symmetric) are also missing. I think they are also 
part of the 'key missing features' that you began to write. (Well, your 
easy key may change the importance of inverse functional properties in 
future, although I have no idea whether those would fit into EL++).

----- OWL-R -----

It is *really* not the way of shooting you:-), but I do not understand 
what you mean by "all the OWL Fullish features of RDFS"; but you say 
that yourself that it is not helpful... If you mean reflection, well, at 
the moment, OWL-R does not have that a.f.a.i.k. (that was the essence of 
the issue I had on the axiomatic triples)... The only thing I see that 
may be possible in OWL-R (well, OWL-R-Full, actually!) is the usage of 
the same symbol for a data and object property. I may miss something...

Personally, I consider OWL-R (and at DL Lite, too, actually) as a kind 
of a minimal set of extra ontology features that I can build on top of 
RDFS, while keeping it still easy both to comprehend and to implement. 
Ie, when you say "OWL-R is ideal for enriching RDF data", I think it is 
not only a true statement but may be _the_ essential feature. Although I 
would add something like "..  with a set of minimal ontological 
statements going beyond RDFS."

Also, I also do not understand why the following is true:

"Compared with DL Lite, OWL-R works better when you have already 
massaged your data into RDF and are working with it as RDF."

(I would not use the word 'massaged' here, b.t.w.) I could very well 
imagine to (1) have my data in RDF (2) add a minimal set of OWL 
statements to further characterize my data and... end up in DL Lite. Ie, 
I do not see that as a differentiating feature from DL Lite. Both are a 
simple extension that works very well on top of RDF data.

I guess this still reflect a difficulty that I still have in making a 
clear high level (ie, user level) distinction between the usage of OWL-R 
and DL Lite. Maybe your remark in OWL-R saying "when the data must be 
massaged by additional rules" is the strongest distinction here... I am 
curious to hear Zhe's opinion.

I think both in the case of DL Lite and OWL-R it is worth emphasizing 
somewhere that they scale very well with the amount of data. (RDF or 
otherwise:-)

B.t.w., you said for DL-Lite: "DL Lite restricts class axioms 
asymmetrically, that is, you can use constructs as the subclass that you 
cannot use as the superclass.". Isn't that statement correct for OWL-R, too?

As for when you ran out of steam: I wonder whether this document should 
talk about the OWL-R-DL and OWL-R-Full differentiation at all. According 
to section 4.4 of the profile document in almost all the cases these two 
coincide in practical use, so the difference between the two is really 
only mathematical, so to say. We could actually say that on the OWL-R 
level the distinction between OWL Full and OWL DL is mostly gone, and 
that is it... But I may have a technical misunderstanding here.

Finally, as for your comments below on what to do with the text: I agree 
that it should not be part of the profile document. However, I am not 
concerned to have this text (plus some examples) being part of the 
primer; actually, on the contrary. The current primer (that I really 
like, do not take me wrong!) may not be easy to read for the 
constituency of possible OWL-R and DL-Lite users. Ie, it would be fairly 
difficult for them to understand what they can and cannot do if the only 
thing we offer is the current primer and the profile spec.

Although your idea to put it as a separate document: that is worth 
considering... A separate primer for EL++, yet another for OWL-R? If we 
had infinite manpower, that might be the best option... But even if we 
do that, I would definitely prefer to keep this at the WG.

Thanks, and have a nice week-end!

Ivan

P.S. We should still find better names for these profiles..


Bijan Parsia wrote:
> 
> Following the vigorous discussion, and even though I have no action here 
> :), I thought I'd try my hand at drafting some text about profiles 
> intended, I think, for the primer. The result is here:
>     http://www.w3.org/2007/OWL/wiki/Profile_Explanations
> 
> (Separated, since I don't want to touch the primer while sandro is 
> getting us to pub. Also, I guess we could drop it into the Profiles doc.)
> 
> It's still fairly preliminary, esp. the descriptions of the individual 
> subsetting profiles. I have some "it's more rdfish" text in the OWL-R 
> section, in spite of the dangers, partially because I couldn't think of 
> anything else at the moment :) So don't shoot me <cough> Ivan  </cough>. ;)
> 
> I suspect that we'll have some sort of cheat sheets for the profiles as 
> well.
> 
> I'm a bit concerned about overloading primer readers with too much 
> detail about the profiles. But I'd also like the profiles document to be 
> very spec like and implementor oriented. One possibility is to break 
> this discussion out into a separate document, either in the WG or in the 
> OWLED Education task force.
> 
> One advantage of moving it out of the WG is that being controversial is 
> rather less damaging. An advantage of moving it out of the primer is 
> that we can include a lot more detail.
> 
> Thoughts?
> 
> Cheers,
> Bijan.
> 

-- 

Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf


Received on Saturday, 12 April 2008 10:08:23 GMT

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