Certain aggregate functions used in
read processed data requests involve picking a single raw sample
from each subinterval as the information returned for the whole subinterval;
for example, minimum value, maximum value, first raw sample, etc. In these
cases, the Ff status of the raw sample picked is also returned.
Other aggregate functions involve the computation of a result that can
involve more than one raw sample; for example, an interpolated value at start
of interval, a time-weighted average. In these cases, a
composite Ff status is returned which summarizes the Ff status
values for the raw samples involved in the computation.
Read raw data requests also return a
composite Ff status for the boundary samples when the boundary
specification requested is
interpolated.
Ff status values comprise three component values:
Quality
- Bad
- Uncertain
- GoodCascade
- GoodNonCascade
Substatus
- NonSpecific
- Other values whose
interpretation depends on Quality
Limits
- Constant
- HighLimited
- LowLimited
- NotLimited
The composite Ff status value returned is a value representing the
worst of individual Ff status values seen. Specifically, each part
of the composite Ff status is computed separately as follows:
- Quality – The
composite Quality value is the worst of Quality values of all the raw sampled
involved. As such:
- GoodCascade is
worse than GoodNonCascade
- Uncertain is
worse than Good Cascade
- Bad is
worse than Uncertain
- Substatus – If the
Quality value AND the Substatus value of all the raw samples involved are
exactly the same, the Substatus is that same value; otherwise a Substatus value
of NonSpecific is returned.
- Limits – The
composite Limit value is a
Limit value OR function of all the individual Limit values from
the raw samples involved.