# comment: looking forward to treatment of units of measure for use in RDF Calendar work

From: Dan Connolly <connolly@w3.org>
Date: Fri, 30 Sep 2005 17:44:32 -0500

Message-Id: <1128120272.28805.15.camel@dirk>
```
We just released a note about the RDF calendar work.
One of the long-standing issues is how to deal with
timezones.

[[
Note that NY:tz timezone is used as a datatype. Earlier, we used
separate properties for time and timezone, which is initially appealing
but problematic for reasons that are detailed in the
InterpretationProperties pattern.
]]
http://www.w3.org/TR/2005/NOTE-rdfcal-20050929/#L21805

There's some sense in which 1pm Chicago time is equal
to 2pm New York time, and it's parallel to the way
10 centimeters is 100 millimeters.

Here's the relevant bit of the InterpretationProperties topic:

[[

An intuitively obvious way to model quantities is:

:building :height [ :magnitude "20"; :units :meter].

But this is a train wreck waiting to happen, because we'd like

[ :magnitude "20"; :units :meter] = [ :magnitude "2000"; :units :centimeter].
:building :height [ :magnitude "2000"; :units :centimeter].

but then we get

:building :height [ :magnitude "20", "2000"; :units :meter, :centimeter]

which is all messed up.

Therefore,

Use InterpretationProperties to relate quantities to magnitudes:

:building :height [ :meters "20"; :centimeters "2000" ].

But

For RdfCalendar, it's not clear whether 11am Chicago time is really the
same as 10am New York time. For iCalendar round-tripping, it's probably
not sufficient to convert everything to Z time, especially when you
consider recurring events.
]]

It occurred to me that this is a problem with n-ary relations, so
I just took another look at
http://www.w3.org/TR/swbp-n-aryRelations/

but I see it's TBD: "For a discussion on how to represent units
and quantities in OWL, please refer to a different note (ref to