Re: [UCR] Rich KR Use Case

Ian - thanks for your comments - I mostly agree.  My comments inlined 
below (I'll use JAH as a tag so they're easier to find in the long 
thread)

At 21:18 +0000 2/22/06, Ian Horrocks wrote:
>On 20 Feb 2006, at 17:58, Jim Hendler wrote:
>
>>
>>  I objected at the beginning to the way this was going, I object 
>>now to how it sounds.  The problems are that (1) this implies that 
>>Rich KR is somehow better and more valuable on the web (largely 
>>unproven),
>
>Jim,
>
>The set of use cases lumped together under this title are pretty 
>heterogeneous. Some do, I agree, emphasise KR on the web more than 
>KR for the web, but I have been assured that the success of this 
>kind of application constitutes a success for the semantic web as a 
>whole, and so could be seen as a relevant input for RIF (not to 
>mention the fact that publishing/sharing ontolgies on the web is an 
>important aspect of many of these use cases). Of the examples 
>available on the Wiki, only the "Uncle" example has been chosen (not 
>by me) for inclusion in the UCR document. I guess that this is 
>because it is well known and relatively easily understood (although 
>I note your comments below). Similar examples also arise in the web 
>services domain (amongst others), and it would be a good idea to at 
>least refer to these in order to strengthen the motivation in 
>general and the "for the web" motivation in particular.
>

JAH: My fear was that the uncle example is more "misunderstood" than 
most others, and thus people may not read it as clearly - one of the 
others would have made me happier.

>
>>  (2) it takes an unflattering approach to describing OWL in its emphasis,
>
>This didn't really strike we when I first read it, but you could be 
>right. It would certainly be a good idea to emphasise the fact that 
>OWL can also express things that are not typically expressible in 
>rule languages, i.e., that the two paradigms have complementary 
>expressiveness. The sentence "A typical example, as detailed below, 
>is the use of rules to describe complex relationships between binary 
>predicates which cannot be captured in ontology languages alone." 
>should also be fixed - it may be true of OWL, but it isn't true of 
>ontology languages in general.
>


JAH: yes.

>
>>   and (3) it doesn't emphasize the important point it is trying to 
>>make (that sometimes extending OWL with rules is a good thing, but 
>>the rules syntax needs to be commensurate with the syntax OWL is in,
>
>For my taste the *really* important point (which also isn't 
>emphasised) is the need for semantic compatibility with RDF and OWL. 
>I'm not sure that I understand what is meant by "commensurate with 
>the syntax OWL is in", and if it means what I think it means (i.e., 
>RDF/XML syntax), then I'm not sure that I agree.
>

JAH: Yes, I would prefer same syntax (so I can have a file which 
mixes my rules and my OWL together when I define both using SWOOP or 
some such editor) but the point I was after here is more the semantic 
compatibility.

>
>>  (4) The syntax used in the example is not the normative exchange 
>>syntax for OWL  and this further obfuscates the point being made.
>
>Again, I guess that you are asking for the example to be given in 
>RDF/XML syntax. The trouble with this is that human readability 
>would then be very poor, even for those reasonably familiar with RDF 
>(which many in the WG and beyond may not be). I guess that the 
>abstract syntax was chosen in an effort to *avoid* obfuscation (I'm 
>not sure about this as I wasn't the originator of this example).
>

JAH: someone who reads the OWL guide and Reference documents should 
be able to read the OWL in this document - I'd rather see 
compatibility than terseness if the goal is to get people to consider 
using these languages together.

>>
>>  I do not object to having a section (Renamed "extending OWL") which
>
>I'm not very keen on the Rich KR name either and, speaking for 
>myself, would be happy to see it changed to "extending OWL".
>
>>   1 - shows how rules can extend something in OWL (I think the 
>>uncle example is very misleading, by the way, unless you want to 
>>get into a discussion of safe grounding - seems odd to have to 
>>insist on including the "person(?y) and person(?x) in the rules 
>>when the WG hasn't even addressed this issue)
>
>I agree that "person(?y) and person(?x)" may not be necessary, but 
>it doesn't seem to be hurting - surely it is reasonable to expect 
>the sibling and child in question to be Persons given that an Uncle 
>must be a Man?

JAH: Ian, if I understand the rules literature as well as I think I 
do, these aren't there to be "typing" statements, they're there to 
be, for lack of a better word, "grounding" statements - i.e. many 
rule languages won't work without them  - even if I say /sibling/ has 
the domain and range of /person/, I still need the person(?x) to make 
sure the ?x is found and bound in most polynomial rule languages (and 
maybe all safe ones) - I'm still grappling with the exact technical 
vocabulary for this, but my understanding is that some people seeing 
this would think we meant something we weren't attempting to convey.

>
>>   2 - that does not have any italics nor use the incorrect word 
>>impossible  (btw, it is more than possible to do this in OWL,, 
>>where I can extend syntax, it is not possible to do this in OWL DL 
>>as written)
>
>Well, I am as big a fan of OWL as the next person, but I do believe 
>that it is "impossible to describe the desired relationship between 
>the hasSibling, hasChild and hasUncle properties in OWL" (either DL 
>or Full). The desired relationship is such that the uncle 
>relationship is entailed for any pair of individuals in the relevant 
>"indirect" relationship. Of course OWL could be extended to include 
>such expressive power (and in fact efforts are already underway to 
>define an extension to OWL DL that includes a limited form of role 
>composition that does not make the language undecidable) - perhaps 
>it would be worth mentioning/discussing this in the text.
>

JAH: the point I was after was the previous one you mentioned about 
them having different coverages - we don't say anything about the 
stuff in OWL being <em>impossible</em> in RIF, and thus it just seems 
like a point was being made that it wasn't necessary to make

>>   3 - makes the last sentence, which is more important than all the 
>>rest of the example, more evident
>
>I agree that this important point is not very prominent (maybe it 
>was deemed to be implicit given the context).
>
>>   4 - is retitled to emphasize that this is about the standard 
>>format for extending, not about the extending per se (there are 
>>many other ways to consider extending languages w/or w/o rules)
>
>Again, I would say that the crucial point is semantic compatibility. 
>I agree that there are many other ways in which OWL could be 
>extended, and that this could/should be mentioned in the text. It 
>doesn't seem unreasonable to focus on rule extensions in this case, 
>however.
>

JAH: point I was making is the one you made earlier, that the focus 
should be on compatibility, not KR.

>>
>>  btw, less anyone wishes to claim my objections here are more 
>>political than technical, I confess you are absolutely right.  THe 
>>WG process is inherently political, and that is why I pay to belong 
>>to the W3C so I can help get the politics right.
>
>I hope I focussed on the technical objections - I prefer to leave 
>political to the experts :-)

JAH: I think I've been insulted very subtly - nicely done Ian!

>
>One point that I remember well from our WOWG days is that, in 
>response to criticism of proposed WG texts, you would usually ask 
>the critic to suggest alternative wording. Perhaps you would like to 
>do so in this case?
>

JAH: umm, well, actually my preference would be to delete this use 
case.  However, since many in the WG seem to want it, I still hope 
there is a consensus space where I would be willing to abstain. but 
until then, my proposed rewording is "delete this section" - sorry.

>Regards,
>
>Ian
>
>
>>
>>   -JH
>>
>>
>>  -- Professor James Hendler			  Director
>>  Joint Institute for Knowledge Discovery	  	  301-405-2696
>>  UMIACS, Univ of Maryland			  301-314-9734 (Fax)
>>  College Park, MD 20742 
>>http://www.cs.umd.edu/~hendler
>>  Web Log: http://www.mindswap.org/blog/author/hendler
>>

-- 
Professor James Hendler			  Director
Joint Institute for Knowledge Discovery	  	  301-405-2696
UMIACS, Univ of Maryland			  301-314-9734 (Fax)
College Park, MD 20742	 		  http://www.cs.umd.edu/~hendler
Web Log: http://www.mindswap.org/blog/author/hendler

Received on Wednesday, 22 February 2006 23:18:30 UTC