Databases Reference
In-Depth Information
Time Period Relationships
Along a Common Timeline
Intersects
Fills
Occupies
Aligns
During
|-----|
|------------|
Starts
Finishes
|-----|
|------------|
|-----|
|-----------|
Figure 14.6 P
1
[occupies] P
2
.
The inverse of this relationship is: P
1
[occupies
1
]P
2
. In the
superscripted relationship, the second time period is the shorter
one. The predicate for this relationship, as it holds between two
time periods expressed as pairs of dates using the closed-open
convention, is:
((eff_beg_dt
1
<¼
eff_beg_dt
2
) AND (eff_end_dt
1
>¼
eff_end_dt
2
))
AND NOT((eff_beg_dt
1
¼
eff_beg_dt
2
) AND (eff_end_dt
1
¼
eff_end_dt
2
))
It says that P
1
doesn't start after P
2
, doesn't end before P
2
, and
doesn't match P
2
. The idea behind it is that there is no clock tick
in P
2
which is not also in P
1
, but that there is at least one clock
tick in P
1
which is not also in P
2
.
Throughout the topic, whenever P
1
[occupies
1
]P
2
, we will
say that P
1
is occupied by P
2
.
Consider the following request for information: which
policies began on or after the Diabetes Management Wellness
Program for 2009 began, and ended on or before that program
ended, but did not both start and end at the same times as
that program started and ended?
