Hi,

I just stumbled upon 
https://groups.google.com/d/topic/sage-support/SlmhkCvo3Ak/discussion

So, there is at least **one** other person somewhere that would enjoy #13268 
getting a review :)

Thanks,
---
Charles Bouillaguet
http://www.lifl.fr/~bouillaguet/



On Nov 26, 2012, at 10:13 PM, Simon King wrote:

> Dear Charles,
> 
> On 2012-11-26, Charles Bouillaguet <charles.bouillag...@gmail.com> wrote:
>> We (at Lille, France) propose to integrate the DifferentialAlgebra into SAGE.
>> This package, which is already present in MAPLE, is the product of years of
>> work from François Boulier et al. on differential elimination. It relies on
>> François's C libraries. Its core is an implementation of the 
>> Rosenfeld-Groebner
>> algorithm, which rewrites systems of differential (or partial derivative)
>> equations into potentially simpler ones. In algebraic terms, it decomposes
>> the radical of a differential ideal into the intersection of prime 
>> differential
>> ideals.
> 
> That's a very valuable contribution, I think!
> 
>> Next, it is not completely clear to us *where* to put this in sage. We 
>> (somewhat
>> arbitrarily) chose to put it in sage.calculus.DifferentialAlgebra, to keep it
>> close with the other functions dealing with differential equations, but we 
>> agree
>> that this is bizarre, because differential elimination is 100% algebraic.
> 
> Differential algebra is a nice example where methods from one
> mathematical field are applied to another mathematical field.
> 
> So, why shouldn't one split the code accordingly and put it into
> *two* parts of Sage?
> 
> I'd suggest you implement the algebraic part in classes, say,
> sage.algebras.differential_algebras.differential_algebra.DifferentialAlgebra 
> and
> sage.algebras.differential_algebras.ideal.DifferentialAlgebraIdeal etc.
> 
> And then, the application to the solution of differential equations may be
> put into sage.calculus.desolvers.rosenfeld_groebner (or whatever
> better name there is): After all, you can easily do "from
> sage.algebras.differential_algebras import ..." in your DE-solver,
> no matter where it is implemented.
> 
> Actually, I think it might even be easier to review if the different
> mathematical topics are cleanly separate in the code base.
> 
> By the way, note that since more or less recently, the
> g-algebras provided by Singular became wrapped in libsingular.
> This is sage.rings.polynomial.plural.NCPolynomialRing_plural.
> Would it make sense to define conversions back and forth between your
> differential algebras and those in libsingular?
> 
> 
>> Lastly, what is the right way to go ? experimental package ?
>> optional package ? We confirmed that it compiles and works on
>> Linux and Mac OS X.
> 
> I think new stuff should first be experimental for a while, and then
> promoted to an optional or even standard spkg. But there may be
> exceptions.
> 
> Best regards,
> Simon
> 
> 
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