W3C home > Mailing lists > Public > public-owl-wg@w3.org > July 2008

Re: draft of LC comment to XML Schema WG

From: Sandro Hawke <sandro@w3.org>
Date: Tue, 29 Jul 2008 12:39:57 -0400
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: public-owl-wg@w3.org
Message-ID: <833.1217349597@ubuhebe>


...
> There are already OWL ontologies that contain dateTime values where the
> timezone is absent.  Such dateTime values may come from different
> documents, and that really have a different notion of what their local
> (unspecified) time is.  The document, however, makes these values all
> equal.
> 
> Our proposed solution to handling such ontologies is to put off the task
> of determining "missing" timezones to tools, with roughly the wording
> that tools MAY accept dateTime values with an absent timezone by
> determining what the "local" timezone is for the value and SHOULD
> produce a warning if they do so; otherwise dateTime values with missing
> timezone are syntax errors.
...

I find this unclear.   My understand of what the WG is saying is this:

      It is a syntax error for an OWL 2 document to contain a dateTime
      value (literal) which is missing timezone information.

      Systems MAY attempt to recover from this error (such as by
      assuming the local time zone), but if they do so, they SHOULD at
      least notify the user.

I would add:

      Such "recovery" will in many cases produce incorrect (unsound)
      results and should be done with caution, since OWL data may come
      from unexpected contexts.  Data providers should be strongly
      encouraged to provide data with timezone information.

     -- Sandro
Received on Tuesday, 29 July 2008 16:40:39 GMT

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