“…In this paper we extend uni cation, the core mechanism of logic programming, to handle bags and sets. When bags and sets are represented with using the union operations, bag and set uni cation is a particular case of AC1and ACI1-uni cation, which has been extensively studied 44,25,24,10,33,18]. Recently, a n umber of uni cation algorithms have been introduced for various domains of bags and sets built with the bag and set constructors similar to the list constructor used in functional and logic programming 21,22,45,9].…”