DTV13 — merger of separate concepts in 8.2.5

Clause 8.2.5 says it is about "time interval sum" and it introduces the concept "time interval plus time interval equals time interval" along with supporting axioms. But it apparently also introduces the concepts "time interval to time interval specifies time interval" and "time interval through time interval specifies time interval", which conceptually have nothing to do with "sum". Further, the UML diagram in Figure 8.8 only shows the 'to time interval' form.

The merger of these two topics is caused by mis-characterizing "time interval through time interval specifies time interval" as a synonymous form for "time interval plus time interval equals time interval". The two verb concepts are co-extensive, but they are different concepts. The time interval that is specified by t1 through t2 is the same time interval as the sum of t1 and t2 as the sum is defined, but its definition is more like "t1 starts t3 and t2 finishes t3". And 't1 to t2' is a relative of 't1 through t2', and its definition is not related to the sum at all.

The two concepts 't1 to t2 specifies t3' and 't1 through t2 specifies t3' should not be in 8.2.5 at all. They should be in a separate section, as another way of specifying time intervals in terms of other time intervals – one that is actually used by business people, while the verbs in 8.2.5, 8.2.6 and 8.2.7 are not.

Make 'time interval1 through time interval2 specifies time interval3' a separate concept

The task force agrees that the ‘sum’ of two time intervals, and the time interval defined by ‘time interval1 through time interval2’ are distinct. The concepts are not even co-extensive, since the latter requires time interval1 to start no later than time interval2.
At the same time, the concept ‘time interval1 to time interval2’ is unrelated to ‘sum’. Clauses 8.2.5 (sum), 8.2.6 (complement), 8.2.7 (intersection) all define means of constructing a time interval from two others. ‘time interval1 to/through time inteval2’ is a fourth means, and should be a separate section (8.2.8).