[QGIS-Developer] QGIS WFS3 Server temporal intervals

Alessandro Pasotti apasotti at gmail.com
Fri Oct 18 03:28:12 PDT 2019


I was thinking about how to better implement this feature for QGIS server
(but it does not need to be restricted to the server).

The WFS3 specs covers pretty much all use cases: you can have features with
a single date/datetime temporal property and a set of date/datetime
properties, the latter case can (not "must"!)  be used to define one (or
many) date/datetime intervals.

Now, the specs say that it's up to the server to decide if only a single
property has to be considered when querying or if multiple properties have
to be combined together to create one (or many) intervals. But since we
code the server it means that it's up to us to decide how to handle it.

Note that the conditions need to be AND(ed) and unless properties values
are equal this does make sense only when multiple properties are combined
to form intervals.

So, the question is how to model this in QGIS?

Since this information may spread over multiple fields, I think it should
go into the QgsVectorLayer class (or some separate temporal settings
companion class/struct).

We can also think to handle "open" intervals, where only one of the
lower/upper values are defined.

I was thinking at a new struct to hold a pair of field names and their role
within the interval and store them as QgsVectorLayer property

To represent a single point-in-time value we could still use an interval
where begin and end are the same field.

Any idea or comment?

(or maybe we do need a QEP?)

Alessandro Pasotti
w3:   www.itopen.it
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