No, we didn't prove exhaustiveness. But as you can see from the
documentation in the test cases we did try and formalize a system for
describing geometric configurations, with the idea that it might lead to
a way of enumerating all possible distinct situations. It would be
interesting to see this pushed through to a proof.
On 5/9/2012 9:32 AM, fork wrote:
Martin Davis<mtnclimb<at> telus.net> writes:
Have a look at:
http://www.vividsolutions.com/jts/tests/index.html
This is a visual interface to the JTS Test Suite, which has a very
complete collection of DE-9IM cases.
Interesting! Seems exhaustive to me. Two comments: Did you prove
exhaustiveness - seems like there should be a way to make a combinatorial
argument about how many possible Clementini matrices are possible (9^4 == 6561,
less impossible combinations)? Also - it might be easier to do confirm
exhaustiveness with simpler shapes, at least for part of the tests. Still,
looks great, and comforts me that you are testing that hard.
As was mentioned, you can use the JTS TestBuilder to build and inspect
test cases. You can drag-and-drop Test Suite XML files onto the
TestBuilder, so it's easy to inspect the cases in the XML tests.
That is cool!
I'm not sure if Wikipedia would appreciate being flooded with DE-9IM
test cases - it doesn't seem like quite the right place for it. The
Vivid site is a good reference as long as it stays up.
I will continue to think about this. I probably don't have time to do fiddle
with this in any systematic way, but a table with every possible matrix, a
picture, and simple code to generate it might be pretty useful.
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