Package nltk :: Package tag :: Module brill :: Class ProximateTokensRule

Class ProximateTokensRule

     object --+        
              |        
yaml.YAMLObject --+    
                  |    
          BrillRule --+
                      |
                     ProximateTokensRule

Known Subclasses:

An abstract base class for brill rules whose condition checks for the presence of tokens with given properties at given ranges of positions, relative to the token.

Each subclass of proximate tokens brill rule defines a method extract_property, which extracts a specific property from the the token, such as its text or tag. Each instance is parameterized by a set of tuples, specifying ranges of positions and property values to check for in those ranges:

(start, end, value)

The brill rule is then applicable to the nth token iff:

The nth token is tagged with the rule's original tag; and
For each (start, end, value) triple:
- The property value of at least one token between n+start and n+end (inclusive) is value.

For example, a proximate token brill template with start=end=-1 generates rules that check just the property of the preceding token. Note that multiple properties may be included in a single rule; the rule applies if they all hold.

Nested Classes

[hide private]

Inherited from yaml.YAMLObject: __metaclass__, yaml_dumper, yaml_loader

Instance Methods

[hide private]

__init__(self, original_tag, replacement_tag, *conditions)
Construct a new brill rule that changes a token's tag from original_tag to replacement_tag if all of the properties specified in conditions hold. source code

Boolean

applies(self, tokens, index)
Returns: True if the rule would change the tag of tokens[index], False otherwise source code

__eq__(self, other)

source code

__ne__(self, other)

source code

__hash__(self)
hash(x)

source code

__repr__(self)
repr(x)

source code

__str__(self)
str(x)

source code

_condition_to_str(self, condition)
Return a string representation of the given condition.

source code

_range_to_str(self, start, end)
Return a string representation for the given range.

source code

Inherited from BrillRule: apply

Inherited from object: __delattr__, __getattribute__, __new__, __reduce__, __reduce_ex__, __setattr__

Class Methods

[hide private]

to_yaml(cls, dumper, data)
Convert a Python object to a representation node.

source code

from_yaml(cls, loader, node)
Convert a representation node to a Python object.

source code

Static Methods

[hide private]

any

extract_property(token)
Returns some property characterizing this token, such as its base lexical item or its tag.

source code

Class Variables

[hide private]

Inherited from yaml.YAMLObject: yaml_flow_style, yaml_tag

Instance Variables

[hide private]

Inherited from BrillRule: original_tag, replacement_tag

Properties

[hide private]

Inherited from object: __class__

Method Details

[hide private]

init(self, original_tag, replacement_tag, conditions)
(Constructor)*

source code

Construct a new brill rule that changes a token's tag from original_tag to replacement_tag if all of the properties specified in conditions hold.

Parameters:

conditions (tuple of (int, int, *)) - A list of 3-tuples (start, end, value), each of which specifies that the property of at least one token between n+start and n+end (inclusive) is value.

Raises: