Allen interval calculus is a way to reason about temporal events.
Here's a simple example: given the following facts:
A patient's fever immediately preceded her cough;
her cough immediately preceded lab values showing hypokalemia;
neutrophilia also immediately preceded the hypokalemia.
One can make queries of the relationships between intervals, for example:
When did her neutrophila occur in relationship with her fever?
define (symptoms)
(set-events '(fever neutrophilia hypokalemia cough))
(set-temporal-relationship 'fever 'cough '(m))
(set-temporal-relationship 'cough 'hypokalemia '(m))
(set-temporal-relationship 'neutrophilia 'hypokalemia '(m))
(get-temporal-relationship 'neutrophilia 'fever)
)
Welcome to Racket v5.3.4.
racket@> ,enter "/Users/keith/medsim/temporal-logic/temporal.rkt"
racket@temporal.rkt> (symptoms)
interval fever
interval neutrophilia
interval hypokalemia
interval cough
'(> mi di si oi)The result list '(> mi di si oi) indicates that several relationships are possible - the episode of neutrophilia either came after the fever (not necessarily immediately after), did come immediately after the fever, started concurrently with the fever, and/or overlapped with the duration of the fever.
This implementation in Racket is based on Stephen Tanimoto's Common Lisp code as described in Chapter 8 ("Commonsense Reasoning") of his book Elements of Artificial Intelligence.
There are 13 possible relationships between intervals, encoded as follows:
"before" <
"after" >
"during" d
"contains" di
"overlaps" o
"overlapped-by" oi
"meets" m
"met-by" mi
"starts" s
"started-by" si
"finishes" f
"finished-by" fi
"equals" =