Syntactic Processing AI
- Syntactic Processing is the step in which a flat input sentence converted into a hierarchical structure that corresponds to the units of meaning in the sentence. This process called parsing.
- It plays an important role in natural language understanding systems for two reasons:
- Semantic processing must operate on sentence constituents. If there is no syntactic parsing step, then the semantics system must decide on its own constituents. If parsing is done, on the other hand, it constrains the number of constituents that semantics can consider.
- Syntactic parsing is computationally less expensive than is semantic processing. Thus it can play a significant role in reducing overall system complexity.
- Although it is often possible to extract the meaning of a sentence without using grammatical facts, it is not always possible to do so.
- Almost all the systems that are actually used have two main components:
- A declarative representation, called a grammar, of the syntactic facts about the language.
- A procedure, called parser that compares the grammar against input sentences to produce parsed structures.
Grammars and Parsers
- The most common way to represent grammars is a set of production rules.
- The first rule can read as “A sentence composed of a noun phrase followed by Verb Phrase”; the Vertical bar is OR; ε represents the empty string.
- Symbols that further expanded by rules called non-terminal symbols.
- Symbols that correspond directly to strings that must found in an input sentence called terminal symbols.
- Grammar formalism such as this one underlies many linguistic theories, which in turn provide the basis for many natural language understanding systems.
- Pure context-free grammars are not effective for describing natural languages.
- NLPs have less in common with computer language processing systems such as compilers.
- Parsing process takes the rules of the grammar and compares them against the input sentence.
- The simplest structure to build is a Parse Tree, which simply records the rules and how they matched.
- Every node of the parse tree corresponds either to an input word or to a non-terminal in our grammar.
- Each level in the parse tree corresponds to the application of one grammar rule.