nltk.sem.evaluate.Model

class documentation

class Model(object): (source)

Constructor: Model(domain, valuation)

A first order model is a domain D of discourse and a valuation V.

A domain D is a set, and a valuation V is a map that associates expressions with values in the model. The domain of V should be a subset of D.

Construct a new Model.

Parameters
domain	A set of entities representing the domain of discourse of the model.
valuation	the valuation of the model.
prop	If this is set, then we are building a propositional model and don't require the domain of V to be subset of D.

Method	`__init__`	Undocumented
Method	`__repr__`	Undocumented
Method	`__str__`	Undocumented
Method	`evaluate`	Read input expressions, and provide a handler for `satisfy` that blocks further propagation of the `Undefined` error. :param expr: An `Expression` of `logic`. :type g: Assignment :param g: an assignment to individual variables...
Method	`i`	An interpretation function.
Method	`satisfiers`	Generate the entities from the model's domain that satisfy an open formula.
Method	`satisfy`	Recursive interpretation function for a formula of first-order logic.
Instance Variable	`domain`	Undocumented
Instance Variable	`valuation`	Undocumented

def __init__(self, domain, valuation): (source) ¶

Undocumented

def __repr__(self): (source) ¶

Undocumented

def __str__(self): (source) ¶

Undocumented

def evaluate(self, expr, g, trace=None): (source) ¶

Read input expressions, and provide a handler for satisfy that blocks further propagation of the Undefined error. :param expr: An Expression of logic. :type g: Assignment :param g: an assignment to individual variables. :rtype: bool or 'Undefined'

def i(self, parsed, g, trace=False): (source) ¶

An interpretation function.

Assuming that parsed is atomic:

if parsed is a non-logical constant, calls the valuation V
else if parsed is an individual variable, calls assignment g
else returns Undefined.

Parameters
parsed	an `Expression` of `logic`.
g:Assignment	an assignment to individual variables.
trace	Undocumented
Returns
a semantic value

def satisfiers(self, parsed, varex, g, trace=None, nesting=0): (source) ¶

Generate the entities from the model's domain that satisfy an open formula.

Parameters
parsed:Expression	an open formula
varex:VariableExpression or str	the relevant free individual variable in `parsed`.
g:Assignment	a variable assignment
trace	Undocumented
nesting	Undocumented
Returns
a set of the entities that satisfy `parsed`.

def satisfy(self, parsed, g, trace=None): (source) ¶

Recursive interpretation function for a formula of first-order logic.

Raises an Undefined error when parsed is an atomic string but is not a symbol or an individual variable.

Parameters
parsed	An expression of `logic`.
g:Assignment	an assignment to individual variables.
trace	Undocumented
Returns
Returns a truth value or `Undefined` if `parsed` is complex, and calls the interpretation function `i` if `parsed` is atomic.

domain: set = (source) ¶

Undocumented

valuation: Valuation = (source) ¶

Undocumented