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Re: Datatype (Map) Conformance Strangeness

From: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
Date: Tue, 14 Apr 2009 09:59:13 +0100
Message-Id: <ECB7283F-8318-428A-9B18-36BB2C69E35D@comlab.ox.ac.uk>
Cc: <public-owl-wg@w3.org>
To: Michael Schneider <schneid@fzi.de>
I have some sympathy with what you say, but I still maintain that  
this is a presentational issue that can be tackled after LC, and that  
we should  minimise changes at this stage. What I did, therefore, was  
to change the name of the section to "Datatype Conformance" (good  
suggestion), and change the text slightly to emphasise that a  
datatype map is just a container for a set of datatypes. This also  
allowed me to avoid mentioning the specifics of the Direct and RDF- 
Based semantics, and to use the OWL 2 datatype map as shorthand for  
the set of datatypes specified in Section 4 of SS&FS.

Datatype map is slightly overloaded in our spec in that it is used to  
mean both a definition of the set of datatypes supported and a  
semantic structure that defines the meaning of a set of datatypes (a  
6-tuple that mixes together the semantics of all the datatypes). We  
might think about changing this in the future. For now, I believe  
that it is sufficient to make it clear what is meant by datatype map  
in a given context. In Conformance it now says "In OWL 2, semantic  
conditions are defined with respect to a set of datatypes specified  
in a datatype map".

Thanks for the careful reading and useful suggestions.

Ian





On 13 Apr 2009, at 22:09, Michael Schneider wrote:

> Hi!
>
> I still believe that we should avoid talking about "datatype maps"  
> in the
> Conformance document, but should talk about "sets of datatypes",  
> instead. I
> think that it doesn't provide any relevant information to readers  
> of this
> document to talk about datatype maps, and it distracts from the really
> relevant bits. Talking about a datatype map instead of a set of  
> datatypes is
> a bit like talking about the bottle, if one really wants to talk  
> about the
> wine inside. A datatype map is more or less just a container for a  
> set of
> datatypes, and the included datatypes are what really counts when  
> we talk
> about conformance.
>
> In particular, I consider it to be more confusing than helpful to  
> say in
> Conformance that there are two notions of a datatype map in our  
> spec. This
> may sound to people as if the set of datatypes supported by the RDF- 
> Based
> Semantics is different from the set of datatypes supported by "OWL 2".
> Neither is this the case nor should it be the case (modulo  
> rdf:XMLLiteral,
> perhaps).
>
> What is actually different are the two definitions of a datatype / 
> map/. But
> my understanding is that a datatype map is mainly an "adapter" to  
> "connect"
> a /set/ of datatypes (for example the OWL 2 datatypes) to an  
> interpretation
> of either the RDF-Based Semantics or the Direct Semantics. And  
> since the
> definitions of an interpretation are different for the two  
> semantics, it
> shouldn't be too surprising that the definitions of a datatype / 
> map/ are (at
> least slightly) different, either.
>
> Nevertheless, there are a still few points, which probably should be
> changed:
>
> * What has been called "OWL 2 Full Datatype Map" is now called "OWL 2
> RDF-Based Datatype Map"
>   <http://www.w3.org/2007/OWL/wiki/RDF-Based_Semantics#def- 
> owldatatypemap>
>
> * Maybe we should at least rename the title of the section to  
> "Datatype
> Conformance" instead of "Datatype Map Conformance".
>
> * It is not really true that the "OWL 2 Datatype Map" is defined in  
> Section
> 4 of the Structural Spec. This section primarily only specifies  
> the /set/ of
> datatypes of OWL 2 and its properties. There is only a slight hint
> concerning datatype /maps/ in the beginning of this section (and I  
> wouldn't
> be unhappy to see it completely removed). The actual definition of the
> datatype /map/ is in Section 2.1 of the Direct Semantics:
> <http://www.w3.org/2007/OWL/wiki/Semantics#Vocabulary>.
>
> Michael
>
>> -----Original Message-----
>> From: Ian Horrocks [mailto:ian.horrocks@comlab.ox.ac.uk]
>> Sent: Monday, April 13, 2009 4:50 PM
>> To: Michael Schneider
>> Cc: public-owl-wg@w3.org
>> Subject: Re: Datatype (Map) Conformance Strangeness
>>
>> I agree with Peter that this is a technical document and not one that
>> I would expect any "user" to be interested in -- it is mainly
>> targeted at implementers of OWL tools who should, I assume, be
>> familiar with terms such as datatype map. So, I don't see mentioning
>> datatype maps here to be inherently problematical.
>>
>> Currently, conformance is the *only* place that specifies what the
>> datatype map has to be when the direct semantics is applied. We can
>> argue about the wisdom of this, but I suggest not to try to change it
>> before LC as there is too much danger that we will just mess things
>> up -- we could always re-organise things later as the change would
>> only be editorial. This being the case, we can't eliminate mention of
>> datatype maps from Conformance. I left this statement mentioning both
>> the OWL Datatype map and the OWL 2 Full Datatype Map as it would look
>> strangely asymmetrical otherwise, and I don't believe that this
>> statement is actually wrong (even if it is redundant).
>>
>> However, it is certainly the case that the note about the datatypes
>> that can occur in conformant OWL DL documents is in the wrong place
>> and should *not* refer to datatype maps but rather to the set of
>> datatypes listed in Section 4 of SS&FS (plus rdfs:Literal). I have
>> therefore moved this note into the Document Conformance section.
>>
>> It is also the case that having Datatype Conformance be a subsection
>> of Document conformance is wrong, as the former talks about semantic
>> conditions and the latter about syntactic ones. I therefore promoted
>> Datatype conformance into its own subsection.
>>
>> I think that the  above mentioned changes are sufficient for the time
>> being -- as I said above, we can think some more about the
>> organisation of these various documents after LC.
>>
>> Ian
>>
>>
>> On 12 Apr 2009, at 08:46, Michael Schneider wrote:
>>
>>> Hi Ian!
>>>
>>> I argued for not talking about "datatype maps" in the Conformance
>>> document
>>> at all. I suggest to just talk about "(sets of) datatypes". My
>>> proposed
>>> revision of the section in my previous mail reflects this.
>>>
>>> I don't see why referring to datatype maps would be necessary or  
>>> would
>>> provide any relevant additional information. We will just open the
>>> Conformance document up to unnecessary criticism.
>>>
>>> I consider datatype maps as an internal aspect of the Direct
>>> Semantics and
>>> the RDF-Based Semantics. So let's talk about datatype maps
>>> exclusively in
>>> the semantics documents. I think it would even be best to not talk
>>> about
>>> datatype maps in the Structural Spec, but, again, only about  
>>> (sets of)
>>> datatypes.
>>>
>>> Michael
>>>
>>>> -----Original Message-----
>>>> From: Ian Horrocks [mailto:ian.horrocks@comlab.ox.ac.uk]
>>>> Sent: Saturday, April 11, 2009 12:42 AM
>>>> To: Michael Schneider
>>>> Cc: public-owl-wg@w3.org
>>>> Subject: Re: Datatype (Map) Conformance Strangeness
>>>>
>>>> I agree with you that this has got rather confused. I think that  
>>>> the
>>>> problem is twofold:
>>>>
>>>> 1) I added the (redundant) note about conformant ontology documents
>>>> in the wrong place -- this could actually be part of the definition
>>>> of an OWL 2 DL ontology document (it is redundant because the
>>>> condition is already one of the conditions that an ontology must
>>>> satisfy in order to be an OWL 2 ontology as specified in Section  
>>>> 3 of
>>>> SS&FS).
>>>>
>>>> 2) Section 2.1.2 is talking about semantic conditions, yet it is in
>>>> the "Document Conformance section.
>>>>
>>>> Thus, I think that the correct way to fix the problem is:
>>>>
>>>> 1) Move the note on datatypes to be part of the definition of an  
>>>> OWL
>>>> 2 DL ontology document (or get rid of it altogether).
>>>>
>>>> 2) Promote 2.1.2 to (sub) section 2.2 (Tool Conformance will then
>>>> become Section 2.3).
>>>>
>>>> I also think that the text should be changed slightly to say:
>>>>
>>>> "In OWL 2, semantic conditions are defined with respect to a  
>>>> datatype
>>>> map. This MUST be either the OWL 2 datatype map (as defined in
>>>> Section 4 of the OWL 2 Syntax specification [OWL 2 Specification]),
>>>> an OWL 2 RDF-Based datatype map (as defined in Section 4.1 of  
>>>> the OWL
>>>> 2 RDF-Based Semantics [OWL 2 RDF-Based Semantics]), or an extension
>>>> of the OWL 2 datatype map to include additional datatypes.
>>>>
>>>> OWL 2 Profiles may support only a reduced set of datatypes. This  
>>>> is,
>>>> however, a syntactic condition that must be met by documents in  
>>>> order
>>>> to fall within the relevant profile, and the semantic conditions on
>>>> the supported datatypes are unchanged, i.e., they are still defined
>>>> by an OWL 2 RDF-Based datatype map or a (possibly extended) OWL 2
>>>> datatype map. These datatype maps define semantic conditions on
>>>> unsupported datatypes, but as these datatypes never occur in
>>>> conforming documents the additional conditions are simply
>>>> irrelevant."
>>>>
>>>> I assume that it is correct to say that semantic conditions may be
>>>> defined by an OWL 2 RDF-Based datatype map -- presumably tools  
>>>> using
>>>> the RDF-Based semantics will use such a datatype map.
>>>>
>>>> Ian
>>>>
>>>>
>>>>
>>>> On 10 Apr 2009, at 16:19, Michael Schneider wrote:
>>>>
>>>>> Hi!
>>>>>
>>>>> I had a closer look at the "Datatype map conformance" section
>>>>> (§2.1.2) in the Conformance document:
>>>>>
>>>>>   <http://www.w3.org/2007/OWL/wiki/index.php?
>>>>> title=Conformance&oldid=21801#Datatype_Map_Conformance>
>>>>>
>>>>> I am pretty confused by the current state. I don't understand why
>>>>> the section refers to the OWL 2 Full datatype map, or to datatype
>>>>> maps at all? The section is still about syntactic conformance, and
>>>>> the only relevant thing here seems to be which datatypes may occur
>>>>> in ontologies.
>>>>>
>>>>> I think, the paragraph confuses two things:
>>>>>
>>>>> 1) The set of datatypes and their properties, i.e. value spaces,
>>>>> lexical spaces, facets. These are specified in the Structural Spec
>>>>> (mainly by referring to XSD and other specifications) and are
>>>>> invariant for the Direct Semantics and the RDF-Based Semantics.
>>>>>
>>>>> 2) The definitions of datatype maps. These definitions are part of
>>>>> the two semantics, and they differ from each other structurally in
>>>>> order to match the different semantic frameworks.
>>>>>
>>>>> I believe only 1) is relevant for Section 2.1.2, while the
>>>>> (different) aspects of datatype maps in 2) have no relevance for
>>>>> syntactic conformance at all.
>>>>>
>>>>> Maybe the confusion already stems from the title that has been
>>>>> chosen for this section (and has been around for a while, I  
>>>>> think):
>>>>> I'd say that it should be changed from "Datatype Map Conformance"
>>>>> to "Datatype Conformance", because datatype /maps/ do not really
>>>>> play a role here, only the /set/ of datatypes supported by OWL  
>>>>> 2 is
>>>>> of relevance.
>>>>>
>>>>> Here is a proposal for a revision of the Section as I think it
>>>>> would be more appropriate:
>>>>>
>>>>>>>>>>>>>> BEGIN PROPOSAL <<<<<<<<<<<<<<<
>>>>>
>>>>> ==== Datatype Conformance ====
>>>>>
>>>>> In OWL 2, semantic conditions are defined with respect to a set of
>>>>> datatypes. This <em title="MUST in RFC 2119 context"
>>>>> class="RFC2119">MUST</em> be either the set of datatypes as  
>>>>> defined
>>>>> in [[Syntax#Datatype_Maps|Section 4]] of the OWL 2 Syntax
>>>>> specification [<cite>[[#ref-owl-2-specification|OWL 2
>>>>> Specification]]</cite>]), or an extension of this set to include
>>>>> additional datatypes.
>>>>>
>>>>> Note that:
>>>>> # A conformant OWL 2 DL ontology document <em title="MUST NOT in
>>>>> RFC 2119 context" class="RFC2119">MUST NOT</em> use datatypes  
>>>>> other
>>>>> than those specified in [[Syntax#Datatype_Maps|Section 4]] of the
>>>>> OWL 2 Syntax specification [<cite>[[#ref-owl-2-specification|OWL 2
>>>>> Specification]]</cite>].
>>>>> # OWL 2 Profiles may support only a reduced set of datatypes. This
>>>>> is, however, a syntactic condition that must be met by  
>>>>> documents in
>>>>> order to fall within the relevant profile, and the semantic
>>>>> conditions on the supported datatypes are unchanged. This also
>>>>> defines conditions on unsupported datatypes, but as these  
>>>>> datatypes
>>>>> never occur in conforming documents the additional conditions are
>>>>> simply irrelevant.
>>>>>
>>>>>>>>>>>>>> END OF PROPOSAL <<<<<<<<<<<<<<<<<
>>>>>
>>>>> Cheers,
>>>>> Michael
>>>
>>> --
>>> Dipl.-Inform. Michael Schneider
>>> Research Scientist, Dept. Information Process Engineering (IPE)
>>> Tel  : +49-721-9654-726
>>> Fax  : +49-721-9654-727
>>> Email: michael.schneider@fzi.de
>>> WWW  : http://www.fzi.de/michael.schneider
>>> ==================================================================== 
>>> ==
>>> =
>>> FZI Forschungszentrum Informatik an der Universität Karlsruhe
>>> Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe
>>> Tel.: +49-721-9654-0, Fax: +49-721-9654-959
>>> Stiftung des bürgerlichen Rechts, Az 14-0563.1, RP Karlsruhe
>>> Vorstand: Prof. Dr.-Ing. Rüdiger Dillmann, Dipl. Wi.-Ing. Michael
>>> Flor,
>>> Prof. Dr. Dr. h.c. Wolffried Stucky, Prof. Dr. Rudi Studer
>>> Vorsitzender des Kuratoriums: Ministerialdirigent Günther  
>>> Leßnerkraus
>>> ==================================================================== 
>>> ==
>>> =
>>>
>
> --
> Dipl.-Inform. Michael Schneider
> Research Scientist, Dept. Information Process Engineering (IPE)
> Tel  : +49-721-9654-726
> Fax  : +49-721-9654-727
> Email: michael.schneider@fzi.de
> WWW  : http://www.fzi.de/michael.schneider
> ====================================================================== 
> =
> FZI Forschungszentrum Informatik an der Universität Karlsruhe
> Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe
> Tel.: +49-721-9654-0, Fax: +49-721-9654-959
> Stiftung des bürgerlichen Rechts, Az 14-0563.1, RP Karlsruhe
> Vorstand: Prof. Dr.-Ing. Rüdiger Dillmann, Dipl. Wi.-Ing. Michael  
> Flor,
> Prof. Dr. Dr. h.c. Wolffried Stucky, Prof. Dr. Rudi Studer
> Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus
> ====================================================================== 
> =
>
Received on Tuesday, 14 April 2009 08:59:52 GMT

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