Survey:Parsing and Parallelization

Parsing is a process of building structure onto a sentence or other string of characters so that the meaning of the sentence or string can be derived. Consider a simple English sentence: ”the boy hit the ball.” Thinking back to elementary school English class, the sentence can be broken into parts of speech as per Figure 1: an article followed by a noun, then a verb, then an article, then a noun. This string of parts of speech can then be grouped into phrases; the article noun pairs grouping to form noun phrases. Additionally the verb and the second noun phrase can be combined to form a verb phrase. Building farther, a sentence is formed from a noun phrase (the subject), and the verb phrase. Then and only then is the string of words recognized as a complete and valid English sentence. Figure 1 displays these steps in a graphical form known as a parse tree. Approaching the same sentence from the other direction, the parse can be started with the desired result, a sentence. A simple valid sentence is made of two parts, a noun phrase (the subject) and a verb phrase. a verb phrase is made up in tern of a verb, and another noun phrase (the predicate). Each simple noun phrase can be further broken down into an article and a noun. Finally, the parts of speech are rewritten with the actual words of the sentence and the parse is completed. The set of rules that define what structures can be derived is called a grammar. These grammars can take many forms, depending on how they are formalized, and how much information is need to be stored in the structure. The type of grammars