Mutable Datasets

• To: visad-list@xxxxxxxxxxxxx
• Subject: Mutable Datasets
• From: "P. Tewson" <ptewson@xxxxxxxxxxxxxxxx>
• Date: Wed, 10 Jul 2002 11:45:03 -0700 (PDT)

Hello,

I'm working on a geo-referenced database that stores environmental
information for ocean environments. As the project progresses, it's
becomming more and more clear that what we really need is a solid data
model on which to base the storage and interface. Having to handle each
data type separately is slowing development.

Since I had used VisAD in the past, I started looking into using the VisAD
data model as a basis for our database. Since visualizing the data is not
a priority, we don't need to make use of most of VisAD's visualization
capability -- just the solid data model. However, I'm running into
problems with the immutability of the datasets. Since our data is
geo-referenced but not regular, I was planning on using an IrregularSet to
store information. However, due to the immutability of all of the Set
classes, adding a single new entry to the thousands already stored seems
like it would require creating entirely new domain sample arrays for the
old points + single new point and creating an entirely new set around that
new sample array.

So, to finally get to the question, is there anything fundamentally wrong
with the ideal of rolling our own MutableIrregularSet class that mimics
the behavior of the IrregularSet class except for allowing dynamic changes
to the domain samples? We would probably have to start sub-classing fairly
far back in the hierarchy (around SimpleSet, it looks like) and replace
the arrays with Vectors or Lists (which will be bad for performance but
hopefully not critical since we aren't visualizing). Would the visad
Delaunay class support a more dynamic approach, or would that require
custom development as well, creating a MutableDelaunay class? I suppose a
MutableFlatField would also be neccessary

Or are we barking up the wrong tree? Is there an easier solution to this
problem, or a package with a more suitable data model?

Thanks for your help,

Patrick Tewson
UW Applied Physics Lab

• Follow-Ups:
  • Re: Mutable Datasets
    • From: Bill Hibbard