Overpass API developpement

[Richard Welty <>]

On 5/3/15 11:53 AM, mmd wrote:
> Hi Richard,
>
> Am 03.05.2015 um 17:16 schrieb Richard Welty:
>> over in the OHM project, we have an interest in extensions to
>> Overpass to support temporal queries. we're not looking for
>> anything really complex right now, just an ability to do tests
>> to see whether or not one date is greater or smaller than another,
>> for fields whose values are ISO format dates.
> I assume this refers to some date in a tag value, like "lastcheck" [1]?
we were thinking start_date and end_date, which we are using
in OHM quite heavily.
>> but before that comes up, probably it's a good idea to figure
>> out what is needed/wanted in the query language, as well
>> as what the semantics should be for queries with abbreviated
>> dates (e.g., comparing a year to a year-month-day).
> There's already a Github ticket [2] on numerical comparison. Based on a
> set of operators like "<", "<=", ">" and ">=" I could think about
> including date values there as well to have a more generalized approach.
this seems quite viable. i'd been looking for those comparisons in
the documentation as it seemed like a good way to start on dates.
> The tricky part will be, how to interpret both tag as well as the query
> value: is it a simple numeric value, a width with some unit of measure
> (possibly with unit conversion required) or maybe some date value in a
> certain format? Next question would be how a reasonable syntax might
> look like in Overpass QL/XML?
i'd say for the moment, focus on ISO date format, and standalone date
values, as this addresses an immediate need in OHM with the least
possible work.

OSM date/time formats are a mess in some places (see opening_hours).
you could spend years trying to sort that stuff out.

probably the thing to do is parse ISO date format into an appropriate
integer, then compare the integers. since OHM goes back potentially
into the distant past, what the baseline should be for the integer
representation is a topic for discussion. good news is that's an internal
thing so we could change it if we need to.

richard

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