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Re: Errors in OWL 2 Profiles specification (and bugs in OWLAPI & OWLAPI Tools profile validator)

From: Ignazio Palmisano <ipalmisano.mailings@gmail.com>
Date: Tue, 25 Aug 2015 13:58:40 +0300
Message-ID: <CAD2jOMMsy8xVfvQWz1mmLexiDWbs7caUBPewA=AhzBuL+kSBrQ@mail.gmail.com>
To: Simon Spero <sesuncedu@gmail.com>, public-owl-comments@w3.org, Owl Dev <public-owl-dev@w3.org>
Cc: "owlapi-developer@lists.sourceforge.net" <owlapi-developer@lists.sourceforge.net>
On 25 August 2015 at 04:12, Simon Spero <sesuncedu@gmail.com> wrote:
> The  investigation of some errors reported in the OWLAPI profile checkers
> (see owlapi issue #435) has revealed what appear to be some errors and
> ambiguities in the OWL 2 Profile Specification document.
> 1. Defined Datatypes
>  All three profiles use the phrase <profile>  "supports the following
> datatypes"
>  EL: §2.2.1
>  QL: §3.2.1
>  RL: §4.2.1
> The OWLAPI profile checkers have been interpreting this as exhaustive
> enumeration.  This is consonant with the corresponding text on data ranges.
>> 2.2.4 Data Ranges
>> "A data range expression is restricted in OWL 2 EL to the predefined
>> datatypes admitted in OWL 2 EL, intersections of data ranges, and to
>> enumerations of literals consisting of a single literal."
>> 3.2.4 Data Ranges
>> A data range expression is restricted in OWL 2 QL to the predefined
>> datatypes and the intersection of data ranges.
>> 4.2.4 Data Ranges
>> A data range expression is restricted in OWL 2 RL to the predefined
>> datatypes admitted in OWL 2 RL and the intersection of data ranges.
> However, all three profiles include the DatatypeDefinition axiom. Either
> this axiom can define Data Ranges which can never be referred to, or, if
> DataType is restricted to the pre-defined types, can only be used to
> illegally attempt to redefine one of those pre-defined types (such
> redefinition is not explicitly prohibited in the Structural Fun Syntax Spec;
> it's just not possible).
> It would seem that the clear intent behind allowing datatype definition
> axioms in the profiles would have been to permit the use of those
> definitions as data ranges where such use would be permitted in OWL 2 DL,
> and that sections [2-4].2.4 are in error.
> 2. Irreflexive Property Axioms in OWL QL
> In the overview of OWL QL features in  §3.1, OWL 2 QL is stated to support
> "reflexive properties (ReflexiveObjectProperty)" and  "irreflexive
> properties (IrreflexiveObjectProperty)".
> However in the detailed specifications of axioms in § 3.2.5 ,
> IrreflexiveObjectProperty is omitted from the production for
> ObjectPropertyAxiom.
> This omission is repeated in the full OWL 2 QL grammar in §6.2. There is
> also no production  for IrreflexiveObjectProperty.
> It is not immediately obvious why IrreflexiveObjectProperty would be
> problematic for QL (there is no transitivity or chains, and reflexivity is
> supported).  Is the omission from the grammar accidental?

That's what I have assumed in the fix described below.

> I am trying to figure out when this divergence happened; reflexivity is not
> mentioned at all in the OWL 1.1  Tractable Fragments submission, and the
> divergence is already present in the first  version of the Profile document
> to appear on the Wiki.
> 3.  OWLAPI bugs
> DisjointClasses axioms were incorrectly flagged as violations of QL and RL.
> (This error had been spotted and fixed for EL in February 2015).
> I believe that these errors were introduced at the end of March 2014.

Yep. My bad.

> Note: I believe that profile checkers are now over-generating (the elements
> in the class are not being checked to see if they are valid subclass
> expressions).  This will be fixed shortly.

Now fixed in version4 branch (soon to be 4.1.0)

> DisjointDataProperties, EquivalentDataProperties and  DataIntersectionOf
> were incorrectly flagged as  violations of RL.
> ReflexiveObjectProperty was incorrectly not flagged as a violation of RL.
> Ignazio Palmisano resolved the ambiguity in (2)  in favor of not flagging
> irreflexive properties as violations of QL by Executive Fiat .

Indeed. To support my decision, I am on the executive board for one
such car, which makes me a Fiat Executive x 10^-7 (rounded up)

> No  action has been taken on issue 1.
> 4. OWLAPI Tools bugs
> (Not Addressed)
> The issues with DisjointClasses are not present in the OWLAPITOOLS version
> of the profile checkers (These errors were introduced when the code was
> integrated into OWLAPI).
> The other issues list above were (and remain) present in the owlapitools
> code.
> Simon

Once the dust settles on issue 1 I'll amend OWLAPITOOLS to do the same
as OWLAPI does.
Received on Tuesday, 25 August 2015 10:59:11 UTC

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