项目网址：http://code.google.com/p/perminusminus/
作者：张开旭（清华大学2012届博士毕业生，毕业论文，现在厦大教学）。
个人主页：http://nlp.csai.tsinghua.edu.cn/~zkx/
源码是python。算法原理是感知器模型。
Introduction
Per-- is a toolkit of AveragedPerceptron (Freund and Schapire, 1999) for path Labelingunder the KISS principle(Keep It Simple andStupid).
Features
Simple and efficient
Multiple usage: path labeling, path finding, sequence labeling and classification
Can provide n-best outputs
Can provide "mar.ginal score"
Can provide alpha (forward) values and beta (backward) values using forward-backward algorithm
Open source