Legacy Issue Number: 16944
Source: Thematix Partners LLC ( Edward Barkmeyer)
The definitions of the weekdays in 9.5.6 simply identify them as 'day of week' time points. ('day of week' is erroneously represented as a name instead of a noun concept) What is being defined in the textDTV is apparently the individual time point, but the UML diagram shows that each day of week time point is in fact a general concept (that corresponds to time intervals). The text should make this clear.
Further, the delimiting property for each of these concepts is specified in a Necessity that is intended to be taken as part of the definition: e.g., Each Tuesday is met by a Monday. That is, the intended definition of the general concept 'Tuesday' is: time interval that is an instance of a calendar day and that is met by an instance of Monday. The definition of the individual concept "Tuesday" is: the time point that has index 2 in the week of days scale, and that is the concept 'Tuesday'. Somehow the text has to make these two definitions clear.
It takes significant effort for the reader to understand that the individual 'Tuesday the time point' can have instances, so that "each Tuesday" makes sense. It may be sufficient to phrase the Necessity as:
Each instance of (time point) Tuesday is met by an instance of (time point) Monday. (SBVR Annex C provides a notation [Tuesday] to refer to the concept as a thing, and CLIF has no problem with the designation (symbol+concept) playing both predicate and argument roles.)
Finally, the following Necessity should appear under 'calendar day' in 9.5.3:
For each calendar, each instance of a 'calendar day' that is defined by the calendar is met by at most one instance of a calendar day that is defined by the calendar. Otherwise, the ontology could technically permit a day to be both a Tuesday and a Friday. It may be that this follows from the necessities for the relationships of the time scales to the Time Axis. If so, the Necessity is not needed, but a Note should mention the sequencing rules.
Reported: DTV 1.0b1 — Thu, 5 Jan 2012 05:00 GMT
Disposition: Resolved — DTV 1.0b2
The last element above, the missing axiom, is added to clause 10.2.
The FTF agrees that the Necessities in 12.3 (was 9.5.6) do not follow from the definitions, and they are not quite accurate as concept definitions: For example, a time interval is a Tuesday if and only if it is a Gregorian calendar day and is met by a Monday. The current definitions just state facts about the concepts. So the text is revised to define the day-of-week time points generally as concepts and relate the terms ‘Monday’, etc., to the time points defined by their positions in the time scale.
This problem was found to apply to the definitions of Gregorian months in 11.3 (was 9.5.5) as well, and this resolution corrects those definitions as well. The month-of-year concepts, however, must be defined individually there is no general definition of the corresponding time intervals.
Updated: Fri, 6 Mar 2015 20:58 GMT
DTV — Weekday definitions are inadequate
- Key: DTV-25
- OMG Task Force: Date-Time (DTV) 1.0 FTF