[seek-kr] ontology figure from abq

Bertram Ludaescher ludaesch at sdsc.edu
Wed Sep 3 09:49:18 PDT 2003


Hi Rich:

Thanks for your insightful message (I think our emails crossed).

I was thinking that *maybe* ecological models such as those found here:
	http://www.gsf.de/UFIS/ufis/modelle.html
could be amenable to dimensional analysis.

Check in particular the sample pages at Amazon: The table of contents
shows a whole section (#3) on Dimensional Analysis in Ecology. I guess 
we should just buy that book to find out:
	http://www.amazon.com/exec/obidos/tg/detail/-/0444892508/104-2454972-2037526?v=glance

btw: The issues that Matt, Peter, etc. have brought up before, are
probably of more immediate importance. But I found that dimension
analysis intriguing.

Bertram


>>>>> "RW" == Rich Williams <rwilliams at nceas.ucsb.edu> writes:
RW> 
RW> There is a widely-used extension of dimensional analysis beyond simply
RW> making sure that the units of terms match up.  It is based on Buckingham's
RW> Pi-theorem, is used extensively in fluid dynamics (that's where I've run
RW> into it) but I haven't seen it used in ecology.  It involves taking a set of
RW> governing equations (the Navier-Stokes eqns in fluid dynamics),
RW> non-dimensionalizing each variable and re-expressing the governing equations
RW> in terms of the non-dimensional variables and various dimensionless
RW> parameters.  The canonical example of a dimensionless parameter in fluid
RW> dynamics is the Reynolds number, which is essentially the ratio of the
RW> inertial forces to the viscous forces in the problem at hand.  By plugging
RW> in estimates for the length scale, time scale, fluid density and viscosity
RW> you can check which forces are likely dominant in the flow regime of
RW> interest, and therefore which terms it's probably safe to toss out of the
RW> governing equations in an attempt to produce a more tractable system.
RW> 
RW> I've never seen this technique applied in ecological models, but I can't
RW> claim to have great breadth of knowledge in the area.  I think one reason it
RW> hasn't been applied is that the basic approach used in ecological modeling
RW> is very different than that used in physical modeling.  For example, in
RW> fluid dynamics, you start with a very complex set of equations that very
RW> precisely express the physics of the system (f=ma and equations of state).
RW> The basic problem is to figure out how to throw stuff out so you can have
RW> some chance of solving the system analytically or numerically.  In the
RW> ecological models I've looked at, the model is built up from a researcher's
RW> interest in understanding the effects of various interacting processes -
RW> there is no 'f=ma' for ecology.  Since the model was developed with the a
RW> priori assumption that a certain set of processes are important, there's
RW> typically no attempt to do a non-dimensionalization and scaling analysis to
RW> make sure that all the terms in the model are important.
RW> 
RW> Rich
RW> 
RW> 
RW> 
RW> -----Original Message-----
RW> From: seek-kr-admin at ecoinformatics.org
RW> [mailto:seek-kr-admin at ecoinformatics.org]On Behalf Of Matt Jones
RW> Sent: Wednesday, September 03, 2003 9:04 AM
RW> To: Bertram Ludaescher
RW> Cc: seek-kr at ecoinformatics.org
RW> Subject: Re: [seek-kr] ontology figure from abq
RW> 
RW> 
RW> Bertram,
RW> 
RW> Yes, dimensional analysis is the correct term for the manipulation of
RW> unit types from STMML.  Its all simple algebra, and is generally taught
RW> early on (I think I first learned it in high school in chemistry). I
RW> don't understand how you plan on 'extending' what Shawn did because what
RW> he did is already dimensional analysis.  What am I missing here?
RW> 
RW> One important area that we have only superficialy considered is the area
RW> of 'dimensionless' numbers.  I think this exposes a lot of the
RW> distinction between 'UnitType' and 'SemanticType', but its pretty muddy
RW> for me.  The problem boils down to this:  dimensionless numbers are
RW> often ratios of two quantities that are measured in the same units.  For
RW> example, grams of Carbon per grams of Nitrogen (the C/N ratio) is
RW> dimensionless because the unit grams cancel.  However, there is
RW> important information that still needs to be captured (e.g., that we are
RW> measuring Carbon and Nitrogen, not Carbon and Oxygen).  This part, the
RW> 'what' that is being measured, is somehow part of the semantic type -- I
RW> think it fits nicely into the diagram I posted to CVS yesterday.  The
RW> problem really crops up when considering 'counts' of things, which is
RW> incredibly common in ecology.  I wrote a bit of a treatise on this topic
RW> with respect to its impact on EML [1], and several people followed up
RW> with some excellent commentary [2] [3] [4].  In [4] Tim Bergsma presents
RW> some interesting ideas about just what a "dimension" is and how it
RW> relates to counts.  In [3] Peter McCartney follows up with ideas about
RW> what might be in a semantic type in EML.  You might find those to be
RW> interesting reading, as I stated that SEEK would be dealing with these
RW> issues head on in that email ;-)
RW> 
RW> Matt
RW> 
RW> [1]http://www.ecoinformatics.org/pipermail/eml-dev/2003-March/000738.html
RW> [2]http://www.ecoinformatics.org/pipermail/eml-dev/2003-March/000744.html
RW> [3]http://www.ecoinformatics.org/pipermail/eml-dev/2003-March/000745.html
RW> [4]http://www.ecoinformatics.org/pipermail/eml-dev/2003-March/000747.html
RW> 
RW> Bertram Ludaescher wrote:
>> 
>> Hi Matt:
>> 
>> Thanks!
>> 
>> Shawn and I had discussed units, unit types, quantities, dimensions
>> and the likes today.
>> 
>> I found some interesting papers on "dimensional analysis" and was
>> wondering whether that could be a natural extension to the simple
>> "reasoning with units" that Shawn has implemented in Prolog.
>> 
>> I found this simple intro quite readable:
>> http://www.physics.uoguelph.ca/tutorials/dimanaly/index.html
>> 
>> The next level seems this:
>> http://www.wikipedia.org/wiki/Dimensional_analysis
>> 
>> which also has a pointer to Buckingham's \pi-theorem
>> 
>> This guy seems to be really ino dim.-analysis:
>> http://www.isd.uni-stuttgart.de/~rudolph/
>> 
>> Also: this book includes a chapter on applying dimensional analysis to
>> ecology:
>> 
RW> http://www.amazon.com/exec/obidos/tg/detail/-/0444892508/104-2454972-2037526
RW> ?v=glance
>> 
>> What do the Eco-folks say? Is this worth investigating further for
>> adding not only unit conversion but more general reasoning and in
>> particular dimensional analysis to SMS?
>> 
>> Bertram
>> 
>> 
>> 
>> 
>>>>>>> "MJ" == Matt Jones <jones at nceas.ucsb.edu> writes:
>> 
MJ> 
MJ> Mark, Bertram, Shawn, and Rich,
MJ> I checked in the diagram that we made in ABQ regarding the carbon flow
MJ> ontology.  It is in CVS:
MJ> seek/docs/figures/seek-cf-measure-ontology.ai
MJ> and in case you don't have Adobe Illustrator:
MJ> seek/docs/figures/seek-cf-measure-ontology.png
MJ> 
MJ> 
MJ> The major change is the addition of "UnitType" to the properties of
MJ> MeasurementType.  I was thinking where "unit" went (as opposed to
MJ> UnitType) and decided it was a property of a particular attribute
RW> rather
MJ> than a MeasurementType.
MJ> 
MJ> This whole thing doesn't really consider nominal and ordinal scale
MJ> things, so we need to determine how MeasurementScale fits in to the
MJ> picture.  But I thought my updated version would be of use to you.
MJ> 
MJ> 
MJ> Matt
MJ> 
MJ> --
MJ> -------------------------------------------------------------------
MJ> Matt Jones                                     jones at nceas.ucsb.edu
MJ> http://www.nceas.ucsb.edu/    Fax: 425-920-2439    Ph: 907-789-0496
MJ> National Center for Ecological Analysis and Synthesis (NCEAS)
MJ> University of California Santa Barbara
MJ> Interested in ecological informatics? http://www.ecoinformatics.org
MJ> -------------------------------------------------------------------
MJ> 
MJ> _______________________________________________
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MJ> seek-kr at ecoinformatics.org
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RW> 
RW> --
RW> -------------------------------------------------------------------
RW> Matt Jones                                     jones at nceas.ucsb.edu
RW> http://www.nceas.ucsb.edu/    Fax: 425-920-2439    Ph: 907-789-0496
RW> National Center for Ecological Analysis and Synthesis (NCEAS)
RW> University of California Santa Barbara
RW> Interested in ecological informatics? http://www.ecoinformatics.org
RW> -------------------------------------------------------------------
RW> 
RW> _______________________________________________
RW> seek-kr mailing list
RW> seek-kr at ecoinformatics.org
RW> http://www.ecoinformatics.org/mailman/listinfo/seek-kr



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