In 1987, the notion of a splicing system was introduced by Tom Head in [ 3] as a mathematical model of restriction enzyme digestion and subsequence religation in the recombination of DNA molecules. 1987年,TomHead发表了一篇论文,引入拼接系统(splicingsystem)的概念作为限制酶与DNA(脱氧核糖核酸)作用、进行DNA重组的数学模型。