Fuzzy Dates & the Digital Humanities

Fuzzy Dates & the Digital Humanities
David Newbury, Lead Developer, Art Tracks, Carnegie Museum of Art
Keystone DH 2017, Philadelphia, PA
A computational and linguistic technique for digitally encoding a
description of when events took place.
David Newbury (@workergnome): Fuzzy Dates & the Digital Humanities.Keystone DH,July 13,2017. 1

What we're going to talk about:
1. How should we think about"when"?
2. Dates! How do they work?
3. How do computers help with this?

Time is the Simplest Thing.
Computer Scientists solved time back in 1971,
when they deﬁned the ﬁrst Thursday in 1970
as the beginning of history.
Nothing important happened before that day,
and history will end on January 19th,2038.
...according to UNIX time.

The humanities take
a slightly more nuanced view.
...Asdoastronomers,geologists,andmymother.

Computability & Correctness
As technologists,we want to to sort and compare using math.
As humanists,we want to maintain the uncertainty of knowledge.
As catalogers,we want an system that's easy to read and write.
These goals are fundamentally in conflict.

Why'd you have to go
and make things
so complicated1
?
1
Lavigne,A.,Christy,L.,Spock,S.,Edwards,G.(2001).Complicated.[Recorded by Lavigne,A.] On LetGo,CD.New York,New
York: Arista.

Thankfully, we're not alone.
Humans have been ﬁguring out ways to
talk about"whens"since January 1,4713 BC.
...when history began.

How do we describe "whens"?
— the 19th Century
— July 15,2016
— The Tokugawa period
— Julian Day 19962.123
— 1499798191 (UNIX Time)
We describe Intervals.

Intervals
An interval is a position and an extent
within a temporal reference system.
If you want to learn more about the theory behind these terms (and much of this talk),
start with Allen Interval Calculus2
and the Time Ontology in Owl3
.
3
Time Ontology in Owl.W3C Candidate Recommendation 06 June 2017.https://www.w3.org/TR/owl-time
2
Towards a general theory of action and time.Artiﬁcial Intelligence 23,pp.123-154..J.F.Allen.1984.

Position & Timelines
It's useful to discuss position
by analogy to Timelines.
A timeline is a number line with a start
position,or epoch,and a clock.

Epochs
The epoch is a deﬁned
starting point for a timeline.
It can be any moment in time
that we can agree to start counting from.
(For example, January 1, 1 CE.)

Clocks
The Clock is a regularly repeating physical
event (a'tick') and a way to count the'ticks'.
Each'tick'is single instance of some
temporal unit.
(Usually, ticks are counted in "seconds", "days", or "years".)

Calendars
A Calendar an algorithm for turning
speciﬁc counts of ticks into human-
readable forms,usually based on the
movement of astronomical bodies.
(1 tick is a day, January has 31 days, a year has 12 months, etc.)

Extent
Extent captures the duration of a interval.
It's typically described with a number
of temporal units,but can also be
described using a calendar.

So—July 15,2016 is an speciﬁc interval:
It has an extent
of 84600 seconds,
and a position
of the 15th day,
of the 7th month,
of the 2016th year
from the epoch
deﬁned by the
Gregorian calendar.

So...who cares?
Computers calculate time using a single clock.
Historians records dates with differing calendars.
This model allows us to describe events and states
using the original calendar from a primary source,
while remaining easily computable.

A brief moment on instants.
Instants are just intervals with a extent of zero,like geometric points.
Forget about them.You don't want to talk about instants—they're
philosophical catnip for people who want to ﬁght about the boundaries
of the imaginary.
(Unless that's your thing...in which case come talk to me afterwards.)
(Bring scotch.)

This is important:
Temporal coordinate systems4
deﬁne"when"
using a position and a extent.
Every position,even one without explicit duration,
has a ﬁnite extent,based on the minimum precision
of the clock.
There are NO moments in time.
4
see http://www.iso.org/iso/isocatalogue/cataloguedetail?csnumber=26013

Circa Dates
considered Harmful.
Circa dates encode a lot of this information—but in your super-secret
special way.

How do computers think about "when"?
Computers use a format called ISO 8601,
which allows dates of varying precision.
2016-07-15
2016-07
2016
These could describe the same instant,
but they're recorded with different units.

Comparing and Sorting dates
Computers really want everything
to be on a single-precision timeline.
2016-07-15
2016-07-01/2016-07-31
2016-01-01/2016-12-31
These are the same instants,but
described using ISO 8601 intervals.

Do you hear that?
It's the sad sound of context being lost.
"Something happened in 2016"
"Something happened between January 1,2016 and December 31,2016"
arenotequivalent.

When you record dates,
you must document
the precision of that date.
Otherwise, knowledge is lost.

Library Folk to the rescue!
Extended Date/Time Format (EDTF) is a
Library of Congress proﬁle/extension to
ISO 8601.5
It deﬁnes a standard for recording
precision & certainty for dates.
5
http://www.loc.gov/standards/datetime/pre-submission.html

Do I have to learn about EDTF?
(Yet another standards document that I have to read...)

Humanized EDTF
As part of the cultural_dates library,
we have a tool that will take April 1990?
and turn it into:
1990-04?
for cataloging as EDTF.

Humanized EDTF
As part of the cultural_dates library,
we have a tool that will take April 1990?
and turn it into:
beginning=1990-04-01; ending=1990-04-31;
precision=month; certain=false
for computational tasks.

Human Readable Forms
For Humanists For Catalogers For Technologists
the 19th century 19xx 1900-01-01/1999-12-31
the 1990s 199x 1990-01-01/1999-12-31
1990 1990 1990-01-01/1990-12-31
October 1990 1990-10 1990-10-01/1999-10-31
October 17,1990 1990-10-17 1990-10-17

Similar work in the ﬁeld:
— Python: https://github.com/ixc/python-edtf
— Ruby: https://github.com/duke-libraries/edtf-humanize
— Javascript: https://github.com/nicompte/edtfy

On to the clever bit!
...but ﬁrst, a bit more theory.

States and Events
A state is a period of time
during which some condition is true.
An event is an instantaneous action
that changes some condition.
States begin and end with events.

States or Events
You can infer either from the other
so there's no need to record both.
Doing so can create paradoxes.
We usually think about states,but we tend
to have documentation about events.

Events: are they really instantaneous?
"ThisworkwaspurchasedinJulyof1850."
Using the described units,the event
took place at an position represented by
July,1850,with an extent of one month.
However,our timeline counts in days,and
July,1850 has an extent of 31 days.

Four Instants, Four Intervals
On a timeline using a speciﬁc clock,
a state can be described using four
instants.
These instants can be combined
into sub-intervals in two ways:
one describing the events,
and the other describing the state.

The Clever Bit.
We can describe the extent of a state
by recording four dates.
These four dates are not just useful for
recording clock precision.
"Purchasedsometimebetween
July15,1850andJuly18,1850.
Soldinthe1950s."

The Really Clever Bit.
Some of these dates can be missing.
"PurchasedbeforeJuly18,1850.
Soldinthe1950s."

Beginning Events
Describing the event that
starts a state:

Ending Events
Describing the event that
completes a state:

Special Cases
Describing speciﬁc cases that result in
with strange grammatical constructions.

So many combinations
"1990 until July 1995"
"the 16th century until sometime after the 1850s"
"sometime between 1990 and 1991 until at least July 15,1995"
You can mix different date precisions and patterns.

ISO 8061, EDTF, and Prose.
The Technologist gets to work with four ISO 8061 dates.
The Cataloger gets to work with one or two EDTF intervals.
The Humanist gets to work with decent,readable prose.
Each can read and write in their preferred form.

The CIDOC-CRM.
If you care about the CIDOC-CRM,
this model is based on and compatible
with their model of temporality.
If you don't care...
please ignore this slide.

Museum Provenance
Documentation on how all this works is at:
http://www.museumprovenance.org/reference/dates

Github
(Mostly) working code is available at:
https://github.com/arttracks/cultural_dates

One Last Thing...
This is not the only computable way to
catalog"when".
Ordinal temporal reference systems
record names,order and relationships,
but not the explicit extent or position.

Thank you.
Art Tracks is a project of Carnegie Museum of Art.
For more details, visit
www.museumprovenance.org
Initial funding for Art Tracks was provided in part by a generous grant by the
Institute of Museum and Library Services.Funding for Phase II has been
provided by the National Endowment for the Humanities with additional
research support provided by the Samuel H.Kress Foundation and the
Paul Mellon Centre for Studies in British Art.

Fuzzy Dates & the Digital Humanities

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