The dependency-based parse trees of dependency grammars see all nodes as terminal, which means they do not acknowledge the distinction between terminal and non-terminal categories.

Thus this dependency-based parse tree acknowledges the subject noun John and the object noun phrase the ball as constituents just like the constituency-based parse tree does.

The constituency-based tree is on the left, and the dependency-based tree on the right:

This aspect of dependency-based structures has allowed DGs, starting with Tesnière ( 1959 ), to focus on hierarchical order in a manner that is hardly possible for constituency grammars.

Each example appears twice, once according to a constituency-based analysis associated with a phrase structure grammar and once according to a dependency-based analysis associated with a dependency grammar.

The final example shows a dependency-based analysis of a sentence where the feature passing path is quite long:

Thus grammars that employ phrase structure rules are constituency grammars (= phrase structure grammars ), as opposed to dependency grammars, which view sentence structure as dependency-based.

An X-bar theoretic understanding of sentence structure is possible in a constituency-based grammar (= phrase structure grammar ) only ; it is not possible in a dependency-based grammar (= dependency grammar ).

It is similar to the System V init system that most Linux distributions use, but uses dependency-based scripts and named run levels rather than numbered ones.

In the corresponding dependency-based structures in the lower row, the left-branching is clear ; the dependent appears to the left of its head, the branch extending down to the left.

This right-branching is completely visible in the lower row of dependency-based structures, where the branch extends down to the right.

The combination of left-and right-branching is now completely visible in both the constituency-and dependency-based trees.

A negative result of this focus on hierarchical order, however, is that there is a dearth of dependency-based explorations of particular word order phenomena, such as of standard discontinuities.

The derivation trees of Tree-adjoining grammar are dependency-based, although the full trees of TAG are constituency-based, so in this regard, it is not clear whether TAG should be viewed more as a dependency or constituency grammar.

In a dependency-based grammar, the distinction is meaningless because dependency-based structures do not acknowledge a finite VP constituent.

For instance, c-command as it is commonly understood can hardly be applied to the dependency-based structures of dependency grammars.

The distinction is hardly present in dependency grammars, since they are dependency-based.

This path is present in both analyses, i. e. in the constituency-based a-analysis on the left and in the dependency-based b-analysis on the right.

* Semantic analysis ( computer science ) – a pass by a compiler that adds semantical information to the parse tree and performs certain checks

The recognizer can be easily modified to create a parse tree as it recognizes, and in that way can be turned into a parser.

Bottom-up parse tree built in numbered steps

The parser builds up the parse tree incrementally, bottom up, and left to right, without guessing or backtracking.

Only the shaded lower-left corner of the parse tree exists.

None of the parse tree nodes numbered 7 and above exist yet.

That shifted symbol becomes a new single-node parse tree.

* A Reduce step applies a completed grammar rule to some of the recent parse trees, joining them together as one tree with a new root symbol.

If the input has no syntax errors, the parser continues with these steps until all of the input has been consumed and all of the parse trees have been reduced to a single tree representing an entire legal input.

In the parse tree example, the phrase A gets reduced to Value and then to Products in steps 1-3 as soon as lookahead * is seen, rather than waiting any later to organize those parts of the parse tree.

# Structured prediction: When the desired output value is a complex object, such as a parse tree or a labeled graph, then standard methods must be extended.

* Parsing: Determine the parse tree ( grammatical analysis ) of a given sentence.

Top-down parsers, on the other hand, hypothesize general parse tree structures and then consider whether the known fundamental structures are compatible with the hypothesis.

Syntax is the study of language structure and phrasal hierarchies, depicted in parse tree format.

Chomsky developed a formal theory of grammar where transformations manipulated not just the surface strings, but the parse tree associated to them, making transformational grammar a system of tree automata.

Depending upon the type of parser that should be generated, these routines may construct a parse tree ( or abstract syntax tree ), or generate executable code directly.

A parse tree is similar to an abstract syntax tree but it will typically also contain features such as parentheses which are syntactically significant but which are implicit in the structure of the abstract syntax tree.

A concrete syntax tree or parse tree or parsing tree

Most XML schema languages are only replacements for element declarations and attribute list declarations, in such a way that it becomes possible to parse XML documents with non-validating XML parsers ( if the only purpose of the external DTD subset was to define the schema ).

A common misconception holds that a non-validating XML parser does not have to read document type declarations, when in fact, the document type declarations must still be scanned for correct syntax as well as validity of declarations, and the parser must still parse all entity declarations in the internal subset, and substitute the replacement texts of internal entities occurring anywhere in the document type declaration or in the document body.

If the XML document type declaration includes any SYSTEM identifier for the external subset, it can't be safely processed as standalone: the URI should be retrieved, otherwise there may be unknown named character entities whose definition may be needed to correctly parse the effective XML syntax in the internal subset or in the document body ( the XML syntax parsing is normally performed after the substitution of all named entities, excluding the five entities that are predefined in XML and that are implicitly substituted after parsing the XML document into lexical tokens ).

This tends to make the output of these KR languages easy for machines to parse, at the expense of human readability and often space-efficiency.

It was based on lib-WWW to download pages, and another program to parse and order URLs for breadth-first exploration of the Web graph.

) Another interchange format, intended to be more compact, easier to parse, and unique for any abstract S-expression, is the " canonical representation " which only allows verbatim strings, and prohibits whitespace as formatting outside strings.

If such a parser exists for a certain grammar and it can parse sentences of this grammar without backtracking then it is called an LL ( k ) grammar.

Languages based on grammars with a high value of k have traditionally been considered to be difficult to parse, although this is less true now given the availability and widespread use of parser generators supporting LL ( k ) grammars for arbitrary k.

Earley parsers in particular have been used in compiler compilers where their ability to parse using arbitrary Context-free grammars eases the task of writing the grammar for a particular language.

This parse tree is simplified ; for more information, see X-bar theory.

* Qtree – LaTeX package for drawing parse trees

Other examples are regression, which assigns a real-valued output to each input ; sequence labeling, which assigns a class to each member of a sequence of values ( for example, part of speech tagging, which assigns a part of speech to each word in an input sentence ); and parsing, which assigns a parse tree to an input sentence, describing the syntactic structure of the sentence.

Analysis of bulk traffic is normally performed by complex computer programs that parse natural language and phone numbers looking for threatening conversations and correspondents.

These rules can be expressed in English, as immediate dominance rules for natural language ( useful for example for programmers in the field of NLP — natural language processing ), or visually as parse trees.

A variant of the CYK algorithm finds the Viterbi parse of a sequence for a given SCFG.

In computing, a parser is one of the components in an interpreter or compiler that checks for correct syntax and builds a data structure ( often some kind of parse tree, abstract syntax tree or other hierarchical structure ) implicit in the input tokens.

* Top-down parsing-Top-down parsing can be viewed as an attempt to find left-most derivations of an input-stream by searching for parse trees using a top-down expansion of the given formal grammar rules.

Although it has been believed that simple implementations of top-down parsing cannot accommodate direct and indirect left-recursion and may require exponential time and space complexity while parsing ambiguous context-free grammars, more sophisticated algorithms for top-down parsing have been created by Frost, Hafiz, and Callaghan which accommodate ambiguity and left recursion in polynomial time and which generate polynomial-size representations of the potentially exponential number of parse trees.

The library cache stores shared SQL, caching the parse tree and the execution plan for every unique SQL statement.

In this way the parsing starts on the Left of the result side ( right side ) of the production rule and evaluates non-terminals from the Left first and, thus, proceeds down the parse tree for each new non-terminal before continuing to the next symbol for a production rule.

That algorithm was extended to a complete parsing algorithm to accommodate indirect ( by comparing previously computed context with current context ) as well as direct left-recursion in polynomial time, and to generate compact polynomial-size representations of the potentially exponential number of parse trees for highly ambiguous grammars by Frost, Hafiz and Callaghan in 2007.