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A parse tree or parsing tree[ 1] (also known as a derivation tree or concrete syntax tree) is an ordered, rooted tree that represents the syntactic structure of a string according to some context-free grammar. The term parse tree itself is used primarily in computational linguistics; in theoretical syntax, the term syntax tree is more common.
This hierarchy can also be seen as a tree: This tree is called a parse tree or "concrete syntax tree" of the string, by contrast with the abstract syntax tree. In this case the presented leftmost and the rightmost derivations define the same parse tree; however, there is another rightmost derivation of the same string S
The existence of multiple derivations of the same string does not suffice to indicate that the grammar is ambiguous; only multiple leftmost derivations (or, equivalently, multiple parse trees) indicate ambiguity. For example, the simple grammar S → A + A A → 0 | 1 is an unambiguous grammar for the language { 0+0, 0+1, 1+0, 1+1 }.
Derivation: The process of recursive generation of strings from a grammar. Parsing: Finding a valid derivation using an automaton. Parse Tree: The alignment of the grammar to a sequence. An example of a parser for PCFG grammars is the pushdown automaton. The algorithm parses grammar nonterminals from left to right in a stack-like manner.
Top-down parsing is a strategy of analyzing unknown data relationships by hypothesizing general parse tree structures and then considering whether the known fundamental structures are compatible with the hypothesis. It occurs in the analysis of both natural languages and computer languages . Top-down parsing can be viewed as an attempt to find ...
Left corner parsing is a hybrid method that works bottom-up along the left edges of each subtree, and top-down on the rest of the parse tree. If a language grammar has multiple rules that may start with the same leftmost symbols but have different endings, then that grammar can be efficiently handled by a deterministic bottom-up parse but ...
Syntactic ambiguity, also known as structural ambiguity, [1] amphiboly, or amphibology, is characterized by the potential for a sentence to yield multiple interpretations due to its ambiguous syntax. This form of ambiguity is not derived from the varied meanings of individual words but rather from the relationships among words and clauses ...
The algorithm, named after its inventor, Jay Earley, is a chart parser that uses dynamic programming; it is mainly used for parsing in computational linguistics. It was first introduced in his dissertation [ 2] in 1968 (and later appeared in an abbreviated, more legible, form in a journal [ 3] ).