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Re: Review of Profiles Document

From: Alan Ruttenberg <alanruttenberg@gmail.com>
Date: Tue, 23 Sep 2008 01:56:50 -0400
Message-ID: <29af5e2d0809222256j3c15b9d5n81174a08df72205b@mail.gmail.com>
To: "Jim Hendler" <hendler@cs.rpi.edu>
Cc: "Ian Horrocks" <ian.horrocks@comlab.ox.ac.uk>, "W3C OWL Working Group" <public-owl-wg@w3.org>
Jim, will you be able to attend the meeting this coming wednesday, so that
we may discuss the comments with the group. We are hoping to vote on
publication of the document in some form.-Alan

On Mon, Sep 22, 2008 at 9:27 PM, Jim Hendler <hendler@cs.rpi.edu> wrote:

>
> This email is my response to the request by Ian to review the Profiles
> document.  I apologize that I didn't have time to do it online and to
> integrate my comments into the document, I also apologize that I did not
> have time to carefully review the language design specs, so I mainly
> concentrate on issues to improve the readability and understandability of
> the document (which could have helped me have time to review the language
> design :-))
>
> here are my comments
>
> overall comments and section 1:
>
> My main metacomment is that there is some material in the document that was
> probably useful in the history of putting it together, and in earlier
> drafts, but which is not needed in the current version - I try to indicate
> these below.  Please note when I suggest something could be deleted that in
> no way means I think it is wrong or misleading or any other negative term,
> rather, the document is quite long and things which add theoretical
> background, without having a direct impact, make it harder to read
>
>  section 2.1 and section 3.1 (the EL and QL feature overviews) could be
> done in the same tabular form as section 4.1 - that would improve
> consistency, but also make comparison of the profiles easier
>
>  the user coming to this document, not familiar with the others, will be
> confused about the mapping to the various syntaxes - the note in the
> introduction (section 1) says
>     OWL 2 profiles are defined by placing restrictions on the OWL 2 syntax
> and then gives some details - but a reader coming to this document alone
> won't necessarily know what that means or what other syntaxes are available.
>  I suggest that a sentence added to this might be helpful -- I would add a
> sentence after  the  sentence above that says something like:
>  "Each of the profiles can be realized through any of the serializations of
> OWL described in our documents including <<Functional, XML, RDF, Manchester
> and any others that I've forgotten>>. "
>
> There is an assumption that the reader is familiar with a number of
> technical terms that are used somewhat differently in different communities
> - for example, in the motivation for OWL 2 EL it says:
>   for which the following reasoning problems can be decided in polynomial
> time: satisfiability, subsumption, classification, and instance checking.
> but, for example, instance checking is not a term used consistently across
> the various literatures of logics (and dbs, for that matter).  I don't think
> we should try to define all these here, but rather should put appropriate
> pointers to Section 5 where these things are defined appropriately (and in
> section 5, I note that terms like "every model of the ontology" are thrown
> around, these could in turn direct people to the model theoretic semantics)
>
>  SECTION 2 - OWL EL:
>
>  I found the sentence in the intro to OWL 2 EL which reads:
>  A main design principle of OWL 2 EL is to focus on the class constructors
> ObjectIntersectionOf and ObjectSomeValuesFrom, but to provide
> ObjectAllValuesFrom only in the form of range restrictions.
>  to be fairly odd - I'd think it should either be motivated or removed -- I
> don't see that it adds anything as a standalone  - if it does stay, please
> note that the definition of range restriction is made in section 2.2.6,
> which comes later, so at least a pointer is necessary to understand the
> comment (my preference would be to delete it as it doesn't really have an
> impact on the definition)
>
>  section 2.2.6 is hard to read - it is hard to tell when the range
> restriction definition ends and where the "additional condition" (mentioned
> in the first sentence of 2.2.6) starts.  Reorganization might help (state
> the condition first and then the definition perhaps) -- I also think that
> the chances of even sophisticated reasoner developers to understand how to
> check this condition will be somewhat limited - I'd suggest an explicit
> pointer to a paper might be useful here.
>
> Section 3 -  OWL QL
>  The second statement sentence of the intro to OWL QL states
>      OWL 2 QL includes most of the main features of conceptual models such
> as UML class diagrams and ER diagrams.
> That is probably debatable, and even if true, could be contentious - I
> suggest an easy fix which is to change "Most" to "Many"
>
>  The description of which kind of DL-Lite this is and the relation to the
> UNA is useful, but I think it should be moved to the end of the discussion
> of QL - having it in the introduction is confusing.  It also makes it easy
> to miss the last sentence of the introduction (about where the constructs
> occur) which is very important.
>
>  The sentence (2nd sentence of Section 3.2):
>     The expressive power of OWL 2 QL is such that the global restriction on
> axioms defined in Section 11 of [OWL 2 Specification] are vacuously
> satisfied in every DL-lite ontology.
> is confusing - even changing  "DL-Lite" to "OWL 2 QL" it is unclear why
> this needs to be stated at this point - is unnecessary to the language
> design.  I would suggest deleting this sentence.
>
>  Section 3.2.5 either has a wording problem or a logic problem - I think it
> is just the former -- above the second syntax box (about object properties)
> it reads:
>     ... and it redefines object property domain and range axioms to use the
> appropriate class expressions.
> and the box talks about object properties.  The next box has text which
> reads:
>   ... nd it redefines the object property domain axioms to use the
> appropriate class expressions.
> but it then only talks about Dataproperties -- I assume that "object"
> should be changed to "data" in the second sentence, but I am not sure
> whether that is sufficient
>
>
> Section 4 OWL RL
>  Section 4.2, the third sentence reads
>    The idea is based on Description Logic Programs [DLP]  a logic obtained
> by intersecting description logics with rule-based languages.
> that is undoubtedly true, but not enlightening at this point - I'd move it
> to the end of the section or delete it (I suggest delete it)
>
>  Section 4.2.5 contains the sentence
>    Keys are redefined in OWL 2 RL to allow for correct type of class
> expression in the axiom.
> which is grammatically incorrect, but I'm not sure what fix is right -
> depends whether there is only one appropriate type (in which case it should
> say "the correct type") or multiple (in which case "types" and "class
> expressions" is needed for agreement) or a mix in which case it needs to be
> reworded.  I think it is the second of these, but I'm not actually sure.
>
> Section 4.3 just above Theorem 1 -- the /may/ (in italics) should be MAY
>
> Theorem 1 seems to me to add nothing importance to the design - if I'm
> missing something I would certainly just assert the conclusion and omit the
> proof - I suggest just deleting it completely (which will also save the work
> of generating the proof sketch).
>
> Section 5
>  I'm willing to believe most of these, but must admit that the ones on OWL
> RL confuse me -- I assume we mean OWL RL restricted to the DL subset and
> doing complete reasoning - is that right?  If so, it might be worth stating
> that explicitly (or at least w/some sort of footnote)
>
>
>
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>
> "If we knew what we were doing, it wouldn't be called research, would it?."
> - Albert Einstein
>
> Prof James Hendler
> http://www.cs.rpi.edu/~hendler
> Tetherless World Constellation Chair
> Computer Science Dept
> Rensselaer Polytechnic Institute, Troy NY 12180
>
>
>
>
>
>
Received on Tuesday, 23 September 2008 05:57:27 GMT

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