Phrase structure grammar

The term phrase structure grammar (English phrase structure grammar ) refers to formal grammars, which break after the constituent principle a set of progressively into smaller units. This model, which essentially corresponds to the Konstituentengrammatik, is used both in the field of theoretical computer science and linguistics and has depending on the application detail differences. Must be distinguished from the dependency grammar, with its stringent mother - daughter association of the words in the decomposition.

Definition of the phrase structure grammar

Noam Chomsky defined the phrase structure grammar formally as a set of production rules ( = phrase structure rules ) over an alphabet and a set of initial strings. The production rules restricted Chomsky so that only exactly one replacement step replaces one symbol of a string and it must not be deleted. Due to this limitation, the phrase structure grammars correspond to the context-sensitive grammars.

The production rules in the sense of Chomsky hierarchy context-sensitive, usually even context-free. According to (ie, context-sensitive and context-free ) are sometimes regarded as phrase structure grammars also in theoretical computer science type 1 and type 2 grammars. However, other authors mean by phrase structure grammars all full formal grammars.

Phrase structure rules

The production rules of the early phrase structure grammar of Chomsky are known as phrase structure rules. These rules could generate syntactic structures according to the following scheme:

This rule specifies that is a constituent A is replaced by the constituents B and C. Based on this scheme, all sets can be created:

With these rules you can create the following sentence: The child drinking a cola. In linguistics it is therefore understood to phrase structure grammars grammars, which consist of such ( or similar ) rules. One can represent the structure of the sentence with the following tree:

This tree shows the decomposition of a sentence into phrases, and their further decomposition to the smallest constituent, usually the words. This process takes place according to the principle of the constituency, which is also the basis of the IC analysis ( immediate constituent analysis).

The following grammars based on the Konstituenzmodell:

Dependenzgrammatiken

There are authors who strictly distinguish between phrase structure and Dependenzgrammatiken: while the first is based on the principle of the constituency, the second from the principle of dependence goes out. In a dependency grammar provides the decomposition of the above theorem as follows:

The following grammars are based on the principle of Dependence: