[API-users] API change proposal: supporting ranges in occurrence eventDate
mblissett at gbif.org
Tue Jan 17 14:28:33 UTC 2023
Dear GBIF API users,
/You might prefer to read this email on either GitHub or the community
forum, as the formatting is probably better:/
/GitHub issue discussion:
/Community forum discussion:
A longstanding issue with the GBIF API is the interpretation and
formatting of the Darwin Core term "eventDate".
*Summary: instead of GBIF changing published |eventDate| values like
|2009-03-18/2009-04-13| and |2010| to |2009-03-18| and |2010-01-01|
respectively, we propose returning the values |2009-03-18/2009-04-13|
and |2010| in the occurrence API and in downloads. Existing code/scripts
that use the |eventDate| value may need to be updated.*
The recommended best practise for the term is "use a date that conforms
to ISO 8601-1:2019" (see https://dwc.tdwg.org/terms/#dwc:eventDate).
ISO 8601-1:2019 supports date ranges, and some publishers provide these.
Examples are |2000-05|, or |2007-11-13/2007-11-15|. GBIF's current
interpretation changes date ranges like this to the first possible day
in the range (|2000-05-01| and |2007-11-13|).
At least 64 million occurrences are affected.
Change to date interpretation
We propose changing the eventDate field in the GBIF API to support ISO
8601-1 date ranges. A range will be returned where one was provided by
the publisher, either directly as a range in the |eventDate| field, or
through a combination of the |year|, |month|, |day|, |startDayOfYear|
and |endDayOfYear| fields.
The data quality checks on dates will be improved to check for
consistency between these fields: |eventDate|, |year|, |month|, |day|,
|startDayOfYear| and |endDayOfYear|. These fields will only be populated
if they are constant for the whole range of dates — a range spanning
several days in January 2020 will have |year=2020|, |month=January| and
|startDayOfYear| and |endDayOfYear| will also be present if the range is
accurate to days.
published event date intepreted eventDate int. year int. month int.
day int. sdoy int. edoy
2023-01-13 2023-01-13 2023 1 13 13 13
2023-01 2023-01 2023 1
2023 2023 2023
2023-01-13/2023-01-14 2023-01-13/2023-01-14 2023 1
2023-01-13/14 2023-01-13/14 2023 1
2023-01/2023-02 2023-01/2023-02 2023
2023-01/02 2023-01/02 2023
2023-01-01/2023-12-31 2023-01-01/2023-12-31 2023
Other cases where we can unambiguously determine a date or date range
will also be handled, for example a record with a |year| and |month| but
no |eventDate|, or non-ISO dates like |January 2023|.
This record <https://api.gbif.org/v1/occurrence/1234530937> (portal link
<https://www.gbif.org/occurrence/1234530937>) is published with
|eventDate=2009-03-18/2009-04-13|, |year=2009|, |month=3|, |day=18|. We
currently change the |eventDate|:
With this proposal, we would preserve the |eventDate| but remove |day|,
as it the event crosses several days:
This record <https://api.gbif.org/v1/occurrence/2382954724> (portal link
<https://www.gbif.org/occurrence/2382954724>) is published with
|eventDate=2019-04-06T20:00:00/2019-04-10T05:00:00| and no separate
|day|, |month| or |year| values. Currently, we process it to this:
Instead, we propose returning this:
The search and download APIs will be affected by this change.
Occurrences will be returned if the occurrence date/date range is
*completely within* the query date or date range.
|Search: eventDate=2023-01-11 Record: eventDate=2023-01-11 -- included
Record: eventDate=2023-01 -- EXCLUDED Record: eventDate=2023-01-11/12 --
EXCLUDED Search: eventDate=2023-01-11,2023-01-12 Record:
eventDate=2023-01-11 -- included Record: eventDate=2023-01 -- EXCLUDED
Record: eventDate=2023-01-11/12 -- included Search: eventDate=*,2023-01
(meaning "Before end of January 2023") Record: eventDate=2023-01-11 --
included Record: eventDate=2023-01 -- included Record:
eventDate=2023-01-11/12 -- included Search: eventDate=2023-01,2023-01
(meaning "After start of January 2023 AND before end of January 2023")
Search: eventDate=2023-01 (same meaning) Record: eventDate=2023-01-11 --
included Record: eventDate=2023-01 -- included Record:
eventDate=2023-01-11/12 -- included |
This implementation will avoid returning occurrences with eventDates
like "2010/2021" in many queries. (There are millions of occurrences
with large ranges like this.)
There is a year filter for the density/pixel maps. An occurrence from
2023-01 will be included, but an occurrence with an eventDate spanning
more than a single year (like 2022-13-31/2023-01-01) will no longer be
Quarterly analytics, global/regional trends
The quarterly analytics include calculations based on the individual
dwc:year, dwc:month and dwc:day fields. The statistics will be affected
where these values change or become blank.
Both libraries will be updated as necessary to support eventDate values
containing a date range.
We have delayed addressing this issue for a long time, primarily due to
concerns about changing the existing behaviour of the API. However, it's
also one of the most frequently requested improvements to GBIF's
If you are aware of software or systems which would have problems
adapting to the proposed change, please let us know, either on this
mailing list, the GitHub issue, the community forum or by email to me.
We will alert users in the same places when the change is ready to be
tested on the test system at api.gbif-uat.org, and when the change is to
be made live on api.gbif.org.
GitHub issue discussion:
Community forum discussion:
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