DTV13 — Issue 19172 continued: Missing "exactly" in scale definitions

This issue started with a complaint about the way that misuse of Structured English in various Necessity statements that are of the form “<time point> has <number> of <class”. Then (on 1 Jan 2014) I noticed an additional problem: typically, the “<time point> of <class>” verb concept is missing, so I proposed adding a verb concept “time period has time point”.

It turns out that this solution is insufficient. It treats a Necessity such as “April has 30 of ‘Gregorian day of month‘” as though it meant “April has 30 of ‘time point‘” – which loses the semantic that the 30 time points that make up April are specifically “Gregorian day of month” time points. (Note: the fact that this is not valid Structured English is the main point of issue 19172).

To fix this, we need instead to add the following verb concepts:

· Gregorian year has Gregorian day of year

· Gregorian year has Gregorian month of year

· Gregorian month of year has Gregorian day of month

We also need to change the definitions of the Gregorian months to make clear that they are such. For example, for January, instead of the definition “time interval that has duration 31 days and that starts an instance of a Gregorian year”, we should use “Gregorian month of year that has duration 31 days and that starts an instance of a Gregorian year”. With this change, “January” is still a ‘time interval’ since a ‘Gregorian month of year’ is ultimately a ‘time interval’.

Part of the Issue is resolved by Issue 13-25; the rest is incorrect.

By substituting the actual “bindable targets” given in the Necessity for the corresponding placeholder terms in the Definition of ‘time point has number of time point kind’, the Necessity
“April has 30 of Gregorian day of month”
is defined by clause 10.4 to mean:
the time point kind ‘Gregorian day of month’ has a finite time scale (Gregorian month of days) and there is a time point sequence that is on the finite time scale and that corresponds to each instance of April, and the first time point of the time point sequence is the index origin member of the finite time scale (Gregorian day of month 1), and 30 is the cardinality of the time point sequence.
In the above, the parenthetical expressions can be inferred from other necessities for the Gregorian month of days time scale.
Thus, interpretation defined by clause 10.4 is not “April has 30 of time point”, as the issue avers. It is rather a description of the subdivision of April into Gregorian day of month time points. This text has been revised and clarified by the resolution to Issue 19172 (now 13-25), and the proposed additions are unnecessary.

The last recommendation in the issue is a consequence of a well-known problem with the SBVR-style definitions of concepts that are instances of concept types. The SBVR definition of a concept describes the properties of each of its instances, that is, the Definition of ‘January’ describes each January. The instances of the concept January are time intervals, not Gregorian months of year (as the issue proposes). So the existing definition is consistent with SBVR practice; the proposed definition is not. The concept ‘January’ is itself an instance of Gregorian month of year, and that relationship is described by the Necessity that follows the Definition.
Thus, no technical change is appropriate. It is not clear to the RTF what editorial notes could be added to avoid creating the misconceptions in the issue. Therefore, no change is proposed.