Hi Stan and all -
Yes, I am thinking about dates in the
context of the observation / monitoring schema.
Here are some of the types of dates that
I've seen in just the data from the NatureServe member programs based on either
lack of available information or interesting data collection
situations.
1) partial dates (only have the year or
year-month) - definitely accommodated by the ISO 8601 format
2) vague dates - for these I
suppose you'd use ISO 8601 in EarliestCollectingDate / LatestCollectingDate,
VerbatimDateTime, and the CollectingDatesInterpreted
flag ?
PRE-1975
post-1992
summer
2001
Mid-1990s
late
1950's
Circa
1941
Early
1990s
3) a range of dates indicating that
collection occurred on a specific date sometime between those two limits and
you're not sure when (example: Observations / collections
from pitfall traps may have date ranges associated with them rather than a
single date. For instance, you can have dates of collection of 19Dec 2004 to
23Jan 2005 and the specimen was from some unknown specific date in that
rage),
4) continuous data collection over a period
of time (some sort of sensor)
5) information
collected on one of two possible dates (one or the other is correct, it's not a
range) (example: aerial surveys flown on either May 27 or June
04, 1999).
It seems that EarliestCollectingDate /
LatestCollectingDate could be used for #3, #4, and #5 - but is there a way to
differentiate between these
as actually being very different types of dates? Would those distinctions just
be communicated using the VerbatimDateTime?
Of course for all of these examples the
fallback would be to use the VerbatimDateTime, but it would be ideal to have as much as
possible of the date information in field(s) that can be queried and
analyzed
Thank you for your thoughts and
help.
Lynn
Hi
Lynn,
Context is everything, so I'm going to assume you are talking about
date/time representations in the observation and monitoring schema(s) that
you are developing. The thinking in the collections community has gone
something along the lines of this:
Concept: the date-time of a collecting event [= recording-event,
gathering-event] -- i.e., when one or more organisms were collected or observed
-- expressed in the common Gregorian calendar, in local
time.
Requirements:
1 -
express the data/time exactly as it was recorded
2 -
retreive records by date/time ranges (date-time greater than X and/or less
than Y)
3 -
accommodate date-times of varying precision, including explicit date-time ranges
(specifying a duration)
4 -
support seasonal (time of year) queries
These
requirements can be met by the following fields:
VerbatimDateTime
EarliestDateCollected
LatestDateCollected
CollectingDatesInterpreted
As
John Wieczorek noted, the ISO 8601 format accommodates varying degrees of
precision. Using a "verbatim date-time" [text string] is as good as you
can do to satisfy the first requirement, short of scanning field notes or voice
recordings. The earliest and latest dates support the recording of
explicit ranges as well as interpreted ranges, which could be used to make
"Summer of 1952" retrievable. The CollectingDatesInterpreted field would
be a boolean field, set as true when the earliest and latest dates represent
interpretations rather than an explicit range. The "DayOfYear" field is a
compromise that we've offered as a simple way to support queries involving
seasonal (annual) cycles; e.g., collected in the northern summer, regardless of
year. But it can be argued that day of year is derivable from
the other fields (unless year is unknown), and that it doesn't accommodate
explicit ranges.
A bit
more documentation is needed to address the odd cases (What do I do when ...?),
but these five fields will support a lot of the data exchange needed for this
concept. These fields are not intended to handle the dating of localities
in paleontology, nor are they intended to handle named periods that are used in
cultural collections (e.g., Iron Age, Victorian).
ABCD uses a few more fields
to handle the concept, http://ww3.bgbm.org/abcddocs/AbcdConcepts but some of these
(date, time, and time zone) are handled by the ISO format, except when the
larger units are unkown; .e.g., the year is unknown, but the day is [ June 16 ];
or the date is unknown, but the time is [ 14:00-15:30 ].
AbcdConcept0860
/DataSets/DataSet/Units/Unit/Gathering/DateTime
AbcdConcept0861
/DataSets/DataSet/Units/Unit/Gathering/DateTime/DateText
AbcdConcept0862
/DataSets/DataSet/Units/Unit/Gathering/DateTime/TimeZone
AbcdConcept0863
/DataSets/DataSet/Units/Unit/Gathering/DateTime/ISODateTimeBegin
AbcdConcept0864
/DataSets/DataSet/Units/Unit/Gathering/DateTime/DayNumberBegin
AbcdConcept0865
/DataSets/DataSet/Units/Unit/Gathering/DateTime/TimeOfDayBegin
AbcdConcept0866
/DataSets/DataSet/Units/Unit/Gathering/DateTime/ISODateTimeEnd
AbcdConcept0867
/DataSets/DataSet/Units/Unit/Gathering/DateTime/DayNumberEnd
AbcdConcept0868
/DataSets/DataSet/Units/Unit/Gathering/DateTime/TimeOfDayEnd
AbcdConcept0869
/DataSets/DataSet/Units/Unit/Gathering/DateTime/PeriodExplicit
The ABCD fields pretty much cover the
entire concept space. One could argue whether time-zone is relevant to the
description of biological phenomena, but we do know that ship trawls do cross
time-zones (including the date-line), and that daylight savings time could
stretch or compress some nocturnal collecting events if their durations
were calculated too simply.
To
some extent these arguments are still going on, so analyze your requirements and
your data, then state your position. ;-)
Cheers,
-Stan
Stanley D. Blum, Ph.D.
Research Information
Manager
California Academy of Sciences
875 Howard St.
San
Francisco, CA
+1 (415) 321-8183
Hi -
I'm working with a suite of date attributes that
can include a combination of precise dates, imprecise dates, and ranges of
dates (and the same types of time values). We'd like to follow existing
standards. If this sort of date / time standard exists, I'd appreciate leads
to the appropriate resources.
Thank you for your help -
Lynn
Lynn Kutner
Data Management
Coordinator
NatureServe
Email: lynn_kutner@natureserve.org
Phone: (303)
541-0360
www.natureserve.org