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: https://github.com/gbif/gbif-api/issues/4#issuecomment-1385497157/
//
/Community forum discussion: https://discourse.gbif.org/t/gbif-api-supporting-ranges-in-occurrence-eventd...
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.
https://gist.github.com/MattBlissett/ff06599559ce86302a6e84d2e3e605ec#change-to-date-interpretation
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 |day=(Blank)|.
|startDayOfYear| and |endDayOfYear| will also be present if the range is accurate to days.
Examples:
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 13 14 2023-01-13/14 2023-01-13/14 2023 1 13 14 2023-01/2023-02 2023-01/2023-02 2023 2023-01/02 2023-01/02 2023 2023/2024 2023/2024 2023-01-01/2023-12-31 2023-01-01/2023-12-31 2023 1 365
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|.
https://gist.github.com/MattBlissett/ff06599559ce86302a6e84d2e3e605ec#api-example
API example:
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|:
"year":2009, "month":3, "day":18, "eventDate":"2009-03-18T00:00:00",
With this proposal, we would preserve the |eventDate| but remove |day|, as it the event crosses several days:
"year":2009, "month":3, "eventDate":"2009-03-18/2009-04-13",
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:
"year":2019, "month":4, "day":6, "eventDate":"2019-04-06T20:00:00",
Instead, we propose returning this:
"year":2019, "month":4, "eventDate":"2019-04-06T20:00:00/2019-04-10T05:00:00", "startDayOfYear":96, "endDayOfYear":100,
https://gist.github.com/MattBlissett/ff06599559ce86302a6e84d2e3e605ec#searching
Searching
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.)
https://gist.github.com/MattBlissett/ff06599559ce86302a6e84d2e3e605ec#density-maps
Density maps
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 included.
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.
https://gist.github.com/MattBlissett/ff06599559ce86302a6e84d2e3e605ec#rgbif-pygbif
rGBIF, PyGBIF
Both libraries will be updated as necessary to support eventDate values containing a date range.
https://gist.github.com/MattBlissett/ff06599559ce86302a6e84d2e3e605ec#feedback
Feedback
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 interpretation.
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.
Thank you,
Matt
GitHub issue discussion: https://github.com/gbif/gbif-api/issues/4#issuecomment-1385497157
Community forum discussion: https://discourse.gbif.org/t/gbif-api-supporting-ranges-in-occurrence-eventd...