Editing Parse tree (section)

==Phrase markers==
Phrase markers, or P-markers, were introduced in early [[transformational generative grammar]], as developed by [[Noam Chomsky]] and others. A phrase marker representing the [[deep structure]] of a sentence is generated by applying [[phrase structure rule]]s. Then, this application may undergo further transformations.

Phrase markers may be presented in the form of [[Tree (data structure)|trees]] (as in the above section on [[#Constituency-based parse trees|constituency-based parse trees]]), but are often given instead in the form of "bracketed expressions", which occupy less space in the memory. For example, a bracketed expression corresponding to the constituency-based tree given above may be something like:

:<math>[_S\ [_\mathit{N}\ \text{John}]\ [_\mathit{VP}\ [_V\ \text{hit}]\ [_\mathit{NP}\ [_\mathit{D}\ \text{the}]\ [_N\ \text{ball}]]]]</math>

As with trees, the precise construction of such expressions and the amount of detail shown can depend on the theory being applied and on the points that the query author wishes to illustrate.