[OEP] Review o Time Ontology editor's draft 18 April 2006

Review o Time Ontology editor's draft 18 April 2006
http://www.w3.org/2001/sw/BestPractices/OEP/Time-Ontology


I enjoyed reading this document; clear and well-written. I
have a number of comments that I hope will help improve it.

Guus


1. begins/ends

[[
begins and ends are relations between instants and temporal
entities, and the beginnings and ends of temporal entities,
if they exist, are unique. In some approach to infinite
intervals, a positively infinite interval has no end, and a
negatively infinite interval has no beginning. Hence, we use
the relations begins and ends in the ontology, rather than
defining functions beginningOf and endOf, since the
functions would not be total. begins, for example, can be
specified as:

:begins
       a       owl:ObjectProperty ;
       rdfs:domain :TemporalEntity ;
       rdfs:range :Instant .
]]

It seems that domain and range should be reversed. An
Instant begins a TemporalEntity, right? I do not understand
the sentence about "beginningOf". Do you mean "hasBegin"
(domain=TemporalEntity, range=Instant)? I would then
understand your objection wrt some intervals not having a
begin/end.


2. DurationDescription

The name "Duration" would be more natural for me, but I
guess this is a matter of style. Same holds for
DateTime/DateTimeDescription.


3. seconds/second property names

For DurationDescription you use properties called "seconds"
"minutes", etc. For DateTimeDescription you use the singular
form ("second","minute"). Do you really need to use two
different sets of properties? I see no reason why you
couldn't use the same property with different local
restrictions for DurationDescription and
DateTimeDescription.


4. use of xsd:duration

Why do you not discuss the use of the datatype xsd:duration,
in similar fashion as later for the datatype xsd:dateTime?
It seems to be part of the OWL file though.

I recall a problem with the semantics of xsd:duration, but
I'm not sure what the status is of this issue.


5. Specification of ":Year"

Suggest to add a note why you prefer to use "maxCardinality
= 0" instead of restricting the values of days, etc. to
0. This might be insightful for the readers.


6. DateTimeDescriptionOf

Why is the domain DateTimeInterval (undefined in the
document, btw), where you use TemporalEntity in the
comparable property DurationDescriptionOf?


7. properties DayOfWeek and DayOfYear

One could argue this is redundant information (as it can be
computed). I assume you add it for convenience, but in that
case I would argue for a range of values such as "Monday",
"Tuesday" (with the possibility to use rdfs:label for other
languages).

The argument of redundancy also holds for DayOfYear.


8.

[[
:January
       a       owl:Class ;
       rdfs:subClassOf :DateTimeDescription ;
       rdfs:subClassOf
               [ a       owl:Restriction ;
                 owl:onProperty :unitType
                 owl:allValuesFrom :unitMonth
               ] ;
      rdfs:subClassOf
               [ a       owl:Restriction ;
                 owl:onProperty :month
                 owl:hasValue 1 ;
               ] .
]]

"owl:allValuesFrom :unitMonth"
   should be
"owl:hasValue :unitMonth".


9. Discrepancies with OWL file
http://www.isi.edu/~pan/damltime/time-entry.owl

There are many discrepancies between the examples in the
document and the OWL time ontology file. To mention a few:

- different names;  e.g. DateTimeDescription is called
   CalendarTimeDescription
- specification of datatypes
- use of InstantThing instead of Instant (and variants of
   this scheme).
- intervalOverlaps vs. intOverlaps

In general, the OWL file covers more than described by the
document. The document should at least be consistent with
the OWL file and preferably cover the full OWL specification
(possibly in appendices).

I would also like to have an overview table in (an appendix
of) the document summarizing all the time-related classes
and properties.


10. Consistent naming

I would prefer a consistent naming scheme, e.g. starting
classes with a capital (UnitSecond) and properties with a
lowercase letter (durationDescriptionOf).



-- 
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Home page: http://www.cs.vu.nl/~guus/

Received on Sunday, 7 May 2006 22:18:21 UTC