Re: Versioning vs Temporal modeling of Patient State

Vipul et al,

my experience is that issues of versioning are quite different from the
issues of temporal modeling. Often in the former case, we don't have to
concern ourselves with what changes have taken place, whereas in the latter
case, we often need to focus on the changes themselves (i.e., questions of
what changes, how, and *when* are critical).

This is an old and difficult problem with systems employing complex
representations of the world. It is often not sufficient to operate within a
mere snapshot of the world. One has to ask whether time (or the changes over
time) matter, or whether at any moment it is sufficient to consider a
snapshot.

One might draw analogies to "compile-time vs. run-time" considerations often
occurring in computer science... in fact, the question of "class changes vs.
instance changes" is exactly that.

BTW, there is a paper that points out that temporal modeling/reasoning is
re-invented/re-implemented over and over because of the lack of "built-in"
support for it in KR systems:

Thomas L. Dean and Drew McDermott. Temporal Data Base Management. Artificial
Intelligence, 32(1):1­55, 1987.

(My comments have to understood in the context that I have a lot of
experience in KR for scheduling and course-of-action planning, where the
problems are predominantly about time and state changes.)

Regards,

    - Ora

-- 
Ora Lassila  mailto:ora.lassila@nokia.com  http://www.lassila.org/
Research Fellow, Nokia Research Center Cambridge
Visiting Scientist, MIT/CSAIL



On 2007-01-11 16:28, "Kashyap, Vipul" <VKASHYAP1@PARTNERS.ORG> wrote:

> 
> 
> Nigam,
> 
> This is an interesting example...
> 
>> Have an example for this one: If the instance is of a the class "Tumor"
>> then
>> on giving treatment it changes in size, shape etc, and might ultimately
>> disappear. On each visit we are observing a different version of the tumor
>> instance [in Tom].
> 
> [VK] Clearly there is a longitudinal aspect to this as the state of the tumor
> changes over time....
> 
> This could be modeled in two ways:
> 
> Tumor1.state = X at time T1
> Tumor1.state = Y at time T2
> ...
> Tumor1.state = "Non-existent" at time Tn
> 
> Essentially you are modeling state as a multivalued property or as a ternary
> relationship (Tumor, state, Time)
> 
> Alternatively,
> 
> Tumor1, v1.state = X
> Tumor1, v2.state = Y
> ...
> Tumor1, vN.state = "Non-existent"
> 
> 
> IMHO, the former representation conveys more information and meaning...
> So, it may make sense not to confound versioning with temporal progression...
> 
> Look forward to the commounities thoughts on the issue.
> 
> Cheers,
> 
> ---Vipul
> 
> 
> 
> 
> 
> 
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Received on Friday, 12 January 2007 15:09:47 UTC