Clarification required: BP5 "describing properties that change over time"

All-

BP5 [1] addresses the situation where the properties of a spatial thing are
updated due to some new measurement or assertion. For example, the boundary
geometry of flooded area will change as the flood levels rise and fall, or
the details of a land parcel may be updated due to a new survey.

In this case, the resource is a spatial thing whose properties are captured
as a series of discrete snapshots through time. Those snapshots may be
created on a fixed schedule (e.g. as a result of an annual survey) or
ad-hoc (e.g. some one notices that things have changed).

There is a second case where properties change over time: when the property
is a time dependent variable that is being measured or estimated according
to some sampling regime. In this case, the resource seems to be a
"time-series" of property values. For example, the water level of a canal,
the wind speed measured at routine intervals by an anemometer, or the GPS
position of a fishing vessel.

(time-series are one-dimensional coverages)

So in the example case of the canal and its water-level, the canal (a
spatial object) has a property "water-level" that refers to a water-level
time-series coverage. As coverages are themselves features (so says OGC et
al) then we can also say that our water-level time-series coverage is also
a spatial thing (albeit a conceptual spatial thing that you can't trip over
in the real world).

Is this second case a valid "possible approach to implementation" that
should be added to BP 5? If so, please can someone in the working group
suggest some criteria as when to use the "property snapshot" pattern (case
1) or the "time-series coverage" pattern (case 2).

(for me it's subjective, but seems to be related to the intent to establish
a coherent sampling regime for a property value as opposed to an ad-hoc
update)

Jeremy

BTW, I've deliberately skipped over the "value assignment" concern (e.g.
how values are assigned to properties) as described in ISO 19109 §7.4.10
ValueAssignment - for example, how OM_Observation can be used to relate the
"observed value" to a "feature of interest" with all the metadata about the
observation or measurement process. I don't think this is relevant for this
BP.


[1]: http://w3c.github.io/sdw/bp/#desc-changing-properties