问题描述
有人可以告诉我什么是有限状态传感器吗?
Can someone please tell me what a finite state transducer is?
我已阅读 Wikipedia文章，但一无所知.
I have read the Wikipedia article and don't understand a thing.
推荐答案
有限状态传感器(FST)是一种有限状态自动机(FSA，FA)，它可以产生输出并读取输入，这对于解析非常有用. (而裸" FSA仅可用于识别，即模式匹配).
A finite state transducer (FST) is a finite state automaton (FSA, FA) which produces output as well as reading input, which means it is useful for parsing (while a "bare" FSA can only be used for recognizing, i.e. pattern matching).
FST由有限数量的状态组成，这些状态由带有输入/输出对标记的转换链接. FST从指定的开始状态开始，并根据输入跳到不同的状态，同时根据其过渡表产生输出.
An FST consists of a finite number of states which are linked by transitions labeled with an input/output pair. The FST starts out in a designated start state and jumps to different states depending on the input, while producing output according to its transition table.
FST在NLP和语音识别中很有用，因为它们具有良好的代数性质，最显着的是它们可以在构图下自由组合(形成代数)，从而在规则关系上实现关系构图(认为这是非确定性函数)组成)，同时保持非常紧凑的外观. FST可以在线性时间内将常规语言解析为字符串.
FSTs are useful in NLP and speech recognition because they have nice algebraic properties, most notably that they can be freely combined (form an algebra) under composition, which implements relational composition on regular relations (think of this as non-deterministic function composition) while staying very compact. FSTs can do parsing of regular languages into strings in linear time.
作为一个例子，我曾经将形态学解析实现为一堆FST.我对动词的主要FST会将常规动词(例如"walked")转换为"walk + PAST".对于动词"to"，我也有一个FST，它将"is"变成"be + PRESENT + 3rd"(第三人称)，其他不规则动词也是如此.使用FST编译器将所有FST合并为一个，生成的FST远小于其各个部分的总和，并且运行速度非常快.可以通过接受扩展的正则表达式语法的各种工具来构建FST.
As an example, I once implemented morphological parsing as a bunch of FSTs. My main FST for verbs would turn a regular verb, say "walked", into "walk+PAST". I also had an FST for the verb "to be", which would turn "is" into "be+PRESENT+3rd" (3rd person), and similarly for other irregular verbs. All the FSTs were combined into a single one using an FST compiler, which produced a single FST that was much smaller than the sum of its parts and ran very fast. FSTs can be built by a variety of tools that accept an extended regular expression syntax.
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