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Ian's review of the Profiles document

From: Boris Motik <boris.motik@comlab.ox.ac.uk>
Date: Wed, 24 Sep 2008 10:32:26 +0100
To: <public-owl-wg@w3.org>
Message-ID: <521BCF4190D84E21B6ED2156D63E1C81@wolf>

Hello,

Ian has sent me his review of the Profiles document and has asked me to pass it on to the WG.

Regards,

	Boris

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- General comment: "OWL 2" is used a lot. Sometimes it seems excessive. E.g., "The following features of OWL 2 are not supported
...". Wouldn't it be enough to say "The following features are not supported ..."? Also, I recall that Ivan asked if we always need
to say, e.g., OWL 2 QL? Perhaps OWL QL would be enough. We could say something in the introduction about this.

- "[OWL 2 EL] captures the expressive power used by many such ontologies and is the maximal subset of OWL 2 for which the basic
reasoning problems (i.e., consistency, satisfiability, subsumption, classification, and instance checking) can be performed in time
that is polynomial with respect to the size of the ontology"
Perhaps a citation would be in order?

- "in particular, rule based engines" 
Suggest deleting the comma.

- "only the productions that differ from [OWL 2 Specification] are presented and the productions that are the same as in [OWL 2
Specification] are not repeated."
Bad style to use a citation in this way. Should be "only the productions that differ from the functional-style syntax [OWL 2
Specification] ..."

- "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."
Suggest but --> and

- The document isn't very consistent in the way it refers to the functional-style syntax. Sometimes it says "the functional-style
syntax [OWL 2 Specification]", sometimes "structural specification [OWL 2 Specification]" (see 2.2.6), sometimes just "[OWL 2
Specification]" (see above), sometimes "OWL 2 [OWL 2 Specification]" (e.g., 2.2.3), and sometimes just "OWL 2" (see 2.2.5). I don't
think that "OWL 2" makes much sense -- what is being described here is also OWL 2!

- In 2.2.6, "Range restrictions on reflexive and transitive roles are generally allowed, unless they are used in axioms that are
explicitly forbidden using the previous definition." could be made clearer!

- "OWL 2 QL is based on the DL-LiteR"
Delete "the".

- "need to impose certain global restriction on the interaction between properties used in different types of axiom"
restriction --> restrictions.

- In 3.1 it says "All axioms in OWL 2 QL are constrained in a way that is compliant with these restrictions. Thus, OWL 2 QL supports
the following axioms:". This doesn't seem very clear. Perhaps better to say "OWL 2 QL supports the following axioms, constrained so
as to be compliant with the above restrictions:"

- It might be useful to say something about why the datatypes are restricted in the way that they are (i.e., to make sure there can
be no restrictions to finite sets of values) -- this would help developers wanting to extend the set of supported datatypes while
retaining the computational properties. This comment also applies to the other profiles.

- In 3.2.3 it says "The subClassExpression production defines the class expressions that can occur in the antecedents of
implications". This could be clearer -- OWL 2 doesn't support implications per se.

- 3.2.5 "Different OWL 2 class axioms from the structural specification [OWL 2 Specification] that refer to the ClassExpression
production, however, are redefined and restricted them to appropriate forms of class expressions." This needs to be translated into
English. Suggest: "Class axioms that refer to the ClassExpression production are, however, redefined so as to use subClassExpression
and/or superClassExpression as appropriate."

- 3.2.5 "... it redefines object property domain and range axioms to use the appropriate class expressions." It would be clearer to
say "... it redefines object property domain and range axioms to use superClassExpression." Moreover, in the following productions,
it uses "superClass" -- presumably this should be "superClassExpression".

- 3.2.5 "OWL 2 QL disallows the functional data property axioms, and it redefines the object property domain axioms to use the
appropriate class expressions." Firstly, "... the functional ..." --> "... functional ...". Secondly, "... appropriate class
expressions" could again be simply superClassExpression. Thirdly, the following productions again use superClass.

- Section 4.2 should be called "Profile Specification" in line with the other profiles.

- 4.2.3 "antecedents of implications" again.

- 4.2.3 "Finally, the equivClassExpressions production ..." --> "Finally, the equivClassExpression production ..."

- 4.2.5 "... property domain and range axioms are restricted to the appropriate form of class expressions." As above -- could say
superClassExpression instead of "appropriate form of class expression".

- 4.2.5. "OWL 2 RL restricts the positive assertions to a particular type of classes, ...". First, "the positive" --> "positive".
Second, "a particular type of classes" --> superClassExpression

- 4.2.5. "Keys are redefined in OWL 2 RL to allow for correct type of class expression in the axiom." Would need a "the" to be
added, but suggest to rephrase as something like "Keys are redefined in OWL 2 RL to allow only subClassExpression in the HasKey
axiom."

- 4.3 "Variables in the implications are preceded with the question mark." --> "Variables in implications are preceded with a
question mark."

- 5 "None of the described profiles, however, is propositionally closed, so these reasoning problems thus can have different
complexity and require different algorithmic solutions." --> "None of the described profiles is, however, propositionally closed, so
these reasoning problems can have different complexity and require different algorithmic solutions."

- 5 The bullet points describing Class Expression Subsumption and Conjunctive Query Answering are missing their full stops.

- 5 "When evaluating the complexity ..." --> "When evaluating complexity ..."

- 5 "the complexity measured with respect to both the size of the axioms and the facts."  "facts" --> "assertions"

- 5 "Table 8 summarizes the known complexity results for OWL 2, ...", but the 1st row of the table is labelled "OWL 2 DL".

- 5 Why is OWL 2 EL italicised in the 1st column?
Received on Wednesday, 24 September 2008 09:34:09 UTC

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