Dear Hellen, dear Nils, On Fri, Mar 15, 2024 at 11:51 PM Nils Bruin <nbr...@sfu.ca> wrote:
> On Friday 15 March 2024 at 15:08:34 UTC-7 Hellen Colman wrote: > > Let me just clarify the main point of his question just in case we can > still obtain a helpful answer. Essentially the question is: Why is Sage > calling "antisymmetric" to a property that is not the standard > antisymmetric property? > > > I agree that a relation gives rise to a graph, but I wouldn't presume that > the standard notion of "antisymmetric" for relations would agree with that > on graphs (or even that there would be a property of graphs that is called > "antisymmetric). So if there is something transferable to be learned for > for students here it is perhaps that terminology is not perfectly aligned > between different areas in mathematics. Given that the word "antisymmetric" > is now taken to mean something specific for graphs (I assume whoever did > that consulted some graph-theory books), it will have considerable inertia > because changing it to something else would break backward compatibility. > I went to look for some references for "antisymmetric graph", and indeed Sage's definition doesn't agree with what I found: <https://www.sciencedirect.com/science/article/pii/0012365X75900928> and <https://arxiv.org/pdf/2208.10727.pdf> I dug up the original vintage commit where this function was introduced: (fortunately, with git it's just git log -S "def antisymmetric(self)" ) commit 0e4f3807f2a18b3a03f47ad35d0aae1c06058fc0 Author: Jason Grout <jason-s...@creativetrax.com> Date: Tue Sep 25 18:46:29 2007 -0500 graphs: added transitive_closure() and antisymmetric(). [...] + def transitive_closure(self): + r""" + Modifies a graph to be its transitive closure and returns the + modified graph. [...] + def antisymmetric(self): + r""" + Returns True if the relation given by the graph is + antisymmetric and False otherwise. + + A graph represents an antisymmetric relation if there being a + path from a vertex x to a vertex y implies that there is not a + path from y to x unless x=y. [...] That is, "antisymmetric" was just a sloppy naming for a different to "antisymmetric graph". I propose the following course of action: 1) copy antisymmetric() to antisymmetric_relation(); deprecate antisymmetric(); introduce antisymmetric_graph(), to mean the standard definition as Hellen points at. 2) after the deprecation period, make antisymmetric() a copy of antisymmetric_graph(), and deprecate the latter 3) after the (2nd) deprecation period, remove antisymmetric_graph() So in the end, in about 2 years, there will be antisymmetric() - conforming to the standard - and antisymmetric_relation() - the original code for old antisymmetric() Cheers Dima > If you feel strongly that a change in terminology would be beneficial, you > could collect some references corroborating your proposed meaning. If > someone else feels strongly enough about preserving the present meaning, > they would likely counter with their own set of references. At that point > hopefully a consensus would grow, with a (slight) preference for the status > quo. If both notions have support, we'd likely look into a way of > supporting both; probably by dangling the appropriate adjectives in front > of "antisymmetric", like "edge_antisymmetric" and "path_antisymmetric" or > something like that. > > For your research, you might be interested in an > is_homotopically_equivalent method. > > -- > You received this message because you are subscribed to the Google Groups > "sage-support" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-support+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sage-support/8b537b0f-d1bb-41eb-95f6-33c8a2c4c3d6n%40googlegroups.com > <https://groups.google.com/d/msgid/sage-support/8b537b0f-d1bb-41eb-95f6-33c8a2c4c3d6n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-support/CAAWYfq37mWomXYd2eRS3MB4oqisaJLskgrZhrSqKP%3DjTHNazrA%40mail.gmail.com.
