Package nltk :: Package parse :: Module chart :: Class EdgeI

type EdgeI

object --+
         |
        EdgeI

Known Subclasses:

A hypothesis about the structure of part of a sentence. Each edge records the fact that a structure is (partially) consistent with the sentence. An edge contains:

A span, indicating what part of the sentence is consistent with the hypothesized structure.
A left-hand side, specifying what kind of structure is hypothesized.
A right-hand side, specifying the contents of the hypothesized structure.
A dot position, indicating how much of the hypothesized structure is consistent with the sentence.

Every edge is either complete or incomplete:

An edge is complete if its structure is fully consistent with the sentence.
An edge is incomplete if its structure is partially consistent with the sentence. For every incomplete edge, the span specifies a possible prefix for the edge's structure.

There are two kinds of edge:

TreeEdges<TreeEdge> record which trees have been found to be (partially) consistent with the text.
LeafEdges<leafEdge> record the tokens occur in the text.

The EdgeI interface provides a common interface to both types of edge, allowing chart parsers to treat them in a uniform manner.

Instance Methods

[hide private]

__init__(self)

source code

(int, int)

span(self)
Returns: A tuple (s,e), where subtokens[s:e] is the portion of the sentence that is consistent with this edge's structure. source code

int

start(self)
Returns: The start index of this edge's span.

source code

int

end(self)
Returns: The end index of this edge's span.

source code

int

length(self)
Returns: The length of this edge's span.

source code

lhs(self)
Returns: This edge's left-hand side, which specifies what kind of structure is hypothesized by this edge.

source code

rhs(self)
Returns: This edge's right-hand side, which specifies the content of the structure hypothesized by this edge.

source code

int

dot(self)
Returns: This edge's dot position, which indicates how much of the hypothesized structure is consistent with the sentence.

source code

Nonterminal or terminal or None

next(self)
Returns: The element of this edge's right-hand side that immediately follows its dot.

source code

boolean

is_complete(self)
Returns: True if this edge's structure is fully consistent with the text.

source code

boolean

is_incomplete(self)
Returns: True if this edge's structure is partially consistent with the text.

source code

__cmp__(self, other)

source code

__hash__(self, other)

source code

Method Details

[hide private]

init(self)
(Constructor)

source code

Overrides: object.__init__: (inherited documentation)

span(self)

source code

Returns: (int, int): A tuple (s,e), where subtokens[s:e] is the portion of the sentence that is consistent with this edge's structure.

start(self)

source code

Returns: int: The start index of this edge's span.

end(self)

source code

Returns: int: The end index of this edge's span.

length(self)

source code

Returns: int: The length of this edge's span.

lhs(self)

source code

Returns:: This edge's left-hand side, which specifies what kind of structure is hypothesized by this edge.

See Also: TreeEdge and LeafEdge for a description of the left-hand side values for each edge type.

rhs(self)

source code

Returns:: This edge's right-hand side, which specifies the content of the structure hypothesized by this edge.

See Also: TreeEdge and LeafEdge for a description of the right-hand side values for each edge type.

dot(self)

source code

Returns: int: This edge's dot position, which indicates how much of the hypothesized structure is consistent with the sentence. In particular, self.rhs[:dot] is consistent with subtoks[self.start():self.end()].

next(self)

source code

Returns: Nonterminal or terminal or None: The element of this edge's right-hand side that immediately follows its dot.

is_complete(self)

source code

Returns: boolean: True if this edge's structure is fully consistent with the text.

is_incomplete(self)

source code

Returns: boolean: True if this edge's structure is partially consistent with the text.

hash(self, other)
(Hashing function)

source code

Overrides: object.__hash__: (inherited documentation)

type EdgeI

__init__(self) (Constructor)

span(self)

start(self)

end(self)

length(self)

lhs(self)

rhs(self)

dot(self)

next(self)

is_complete(self)

is_incomplete(self)

__hash__(self, other) (Hashing function)

init(self)
(Constructor)

hash(self, other)
(Hashing function)