This is now https://github.com/sagemath/sage/issues/37618
On Sat, Mar 16, 2024 at 12:42 PM Dima Pasechnik <dimp...@gmail.com> wrote: > 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/CAAWYfq2YvkNOCO2TK1Ta-q1ZdfJX%3DR5iC_sLsuOKtmRy%3DYHmMQ%40mail.gmail.com.
