,
Ilay Tzarfati
Creative Commons Attribution 4.0 International license
The well known Normalized Edit Distance (ned) [Marzal and Vidal 1993] is known to disobey the triangle inequality on contrived weight functions, while in practice it often exhibits a triangular behavior. Let d be a weight function on basic edit operations, and let ned_{d} be the resulting normalized edit distance. The question what criteria should d satisfy for ned_{d} to be a metric is long standing. It was recently shown that when d is the uniform weight function (all operations cost 1 except for no-op which costs 0) then ned_{d} is a metric. The question regarding non-uniform weights remained open. In this paper we answer this question by providing a necessary and sufficient condition on d under which ned_{d} is a metric.
@InProceedings{fisman_et_al:LIPIcs.CPM.2024.14,
author = {Fisman, Dana and Tzarfati, Ilay},
title = {{When Is the Normalized Edit Distance over Non-Uniform Weights a Metric?}},
booktitle = {35th Annual Symposium on Combinatorial Pattern Matching (CPM 2024)},
pages = {14:1--14:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-326-3},
ISSN = {1868-8969},
year = {2024},
volume = {296},
editor = {Inenaga, Shunsuke and Puglisi, Simon J.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CPM.2024.14},
URN = {urn:nbn:de:0030-drops-201247},
doi = {10.4230/LIPIcs.CPM.2024.14},
annote = {Keywords: Normalized Edit Distance, Non-uniform Weights, Triangle Inequality, Metric}
}