Pattern matching algorithms for streaming data

想象一下，我给你的任务如下：阅读莎士比亚全集，并写下所有出现的短语My Good Lord。这项任务在计算机科学中被称为精确模式匹配；在这里，短语我的好主人就是模式。如果我让你找出所有与我的好主相似的短语，你可以决定写下我的尊贵的主，我仁慈的主和简单的主。这是一个近似的模式匹配问题，其复杂性当然取决于我们如何定义相似这个词。考虑的定义取决于应用，视野的广度和深度很大程度上源于此。现在想象一下，我将为你们朗读莎士比亚全集，并期待你们写下你们听到的类似短语。这是在线近似模式匹配，也是本方案的重点。这项提议适用于与互联网相关的应用程序，其中大量数据不断地通过计算机--这一领域被称为数据流。在这里，数据太大，无法存储，结果必须在数据到达时动态计算。在阅读类比中，如果你听错了一段话，我不会重读给你听。这项建议的目的是将这些字段结合在一起，在流数据中快速搜索模式。继续这个类比，我们将考虑在几种情况下找到模式：1.像以前一样，我会给你读一本书，但这一次要快得多。我知道你不能足够快地写下所有发生的事情，但我想要你保证你会抓住大多数。很多人会同时为你朗读书籍。每当他们中的任何一个人说出你正在寻找的图案时，你都必须把它写下来。我要给你读一本书，但我不承诺按顺序阅读：第6页第3行第6字是好的，第39页第1行第2字是快乐的，第6页第3行第5字是我的…当然，这些问题听起来很奇怪，用简单的英语表达出来是违反直觉的，但潜在的计算机科学问题对于许多新兴的应用程序，如流量整形、防火墙、互联网监控和恶意内容检测都是非常重要的。

Imagine that I give you the following task: read the Complete Works of Shakespeare and write down all occurrences of the phrase my good lord . The task is known in Computer Science as exact pattern matching; here the phrase my good lord is the pattern. If I asked you to find all phrases similar to the phrase my good lord , you may decide write down the phrases my noble lord , my gracious lord and simply my lord . This is approximate pattern matching, a problem whose complexity is, of course, dependent on how we define the word similar. The definition considered depends on the application and much of the breadth and depth of the field arises from this.Now imagine that I am going to read the Complete Works of Shakespeare to you and expect you to write down similar phrases as you hear them. This is online approximate pattern matching and is the focus of this proposal. The proposal is applicable to Internet related applications where a vast quantity of data passes though a computer constantly - a field known as data streaming. Here the data is far too large to be stored and results must be computed on the fly as the data arrives. In the reading analogy, if you mishear a paragraph, I'm not going to reread it to you.The aim of this proposal is to bring these fields together to search for patterns quickly in streaming data. Continuing the analogy, we will be considering finding patterns in a number of circumstances:1. As before I am going to read you a book but this time much faster. I know that you can't write down all the occurrences fast enough but I want you to guarantee you will catch most of them.2. Many people will read books out loud to you at the same time. Any time any of them say the pattern you are looking, for you have to write it down.3. I am going to read you a book but I make no promise to read the words in order: page 6 line 3 word 6 is good , page 39 line 1 word 2 is happy , page 6 line 3 word 5 is my ...Of course, these problems sound strange and counter-intuitive phrased in plain English, but the underlying Computer Science problems are highly significant for many emerging applications such as traffic shaping, firewalls, Internet monitoring and malicious content detection.