Abstract
Consider a dynamic network and a given distributed problem. At any point in time, there might exist several solutions that are equally good with respect to the problem specification, but that are different from an algorithmic perspective, because some could be easier to update than others when the network changes. In other words, one would prefer to have a solution that is more robust to topological changes in the network; and in this direction the best scenario would be that the solution remains correct despite the dynamic of the network.
In [Arnaud Casteigts et al., 2020], the authors introduced a very strong robustness criterion: they required that for any removal of edges that maintain the network connected, the solution remains valid. They focus on the maximal independent set problem, and their approach consists in characterizing the graphs in which there exists a robust solution (the existential problem), or even stronger, where any solution is robust (the universal problem). As the robustness criteria is very demanding, few graphs have a robust solution, and even fewer are such that all of their solutions are robust. In this paper, we ask the following question: Can we have robustness for a larger class of networks, if we bound the number k of edge removals allowed?
To answer this question, we consider three classic problems: maximal independent set, minimal dominating set and maximal matching. For the universal problem, the answers for the three cases are surprisingly different. For minimal dominating set, the class does not depend on the number of edges removed. For maximal matching, removing only one edge defines a robust class related to perfect matchings, but for all other bounds k, the class is the same as for an arbitrary number of edge removals. Finally, for maximal independent set, there is a strict hierarchy of classes: the class for the bound k is strictly larger than the class for bound k+1.
For the robustness notion of [Arnaud Casteigts et al., 2020], no characterization of the class for the existential problem is known, only a polynomialtime recognition algorithm. We show that the situation is even worse for bounded k: even for k = 1, it is NPhard to decide whether a graph has a robust maximal independent set.
BibTeX  Entry
@InProceedings{dubois_et_al:LIPIcs.SAND.2023.7,
author = {Dubois, Swan and Feuilloley, Laurent and Petit, Franck and Rabie, Mika\"{e}l},
title = {{When Should You Wait Before Updating?  Toward a Robustness Refinement}},
booktitle = {2nd Symposium on Algorithmic Foundations of Dynamic Networks (SAND 2023)},
pages = {7:17:15},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {9783959772754},
ISSN = {18688969},
year = {2023},
volume = {257},
editor = {Doty, David and Spirakis, Paul},
publisher = {Schloss Dagstuhl  LeibnizZentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/opus/volltexte/2023/17943},
URN = {urn:nbn:de:0030drops179435},
doi = {10.4230/LIPIcs.SAND.2023.7},
annote = {Keywords: Robustness, dynamic network, temporal graphs, edge removal, connectivity, footprint, packing/covering problems, maximal independent set, maximal matching, minimum dominating set, perfect matching, NPhardness}
}
Keywords: 

Robustness, dynamic network, temporal graphs, edge removal, connectivity, footprint, packing/covering problems, maximal independent set, maximal matching, minimum dominating set, perfect matching, NPhardness 
Collection: 

2nd Symposium on Algorithmic Foundations of Dynamic Networks (SAND 2023) 
Issue Date: 

2023 
Date of publication: 

12.06.2023 