org.aspic.inference
Class Rule

java.lang.Object
  org.aspic.inference.Element
      org.aspic.inference.Constant
          org.aspic.inference.Term
              org.aspic.inference.Rule

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable

public class Rule
extends Term

A Rule is a specialised Term, rule/4. The four parameters are:

• parameter 1: consequent (a Constant or Term)
• parameter 2: antecedent (an ElementList of Constants or Terms)
• parameter 3: degree of belief, dob (a numeric Constant)
• parameter 4: rule name (a Constant)

Rule is also the only class that is explicitly allowed into the Knowledge Base.

The first two parameters arise naturally from a prolog (i.e. horn clause based) rule system. The last two parameters fix us into the argumentation space and need some explanation.

dob allows us to place an ordering over arguments that are developed from facts and rules,List when we develop those arguments using a particular evaluation strategy (i.e. weakest_link or last_link).

name allows a particular rule to be undercut by other rules and facts. It is itself a Term and can be thought of as a "hidden premise". because when developing an argument based on a rule, the algorithm checks that it can develop arguments for each of the rule's premises (members of the antecedent) *and* it's name.

A knowledge base is a collection of Rules

A KnowledgeBase contains a list of rules. Facts and beliefs are represented in a KnowledgeBase as Rules with an empty antecedent. In order to distinguish between proper rules (i.e. those that have non-empty antecendents) and facts/beliefs a helper method, isFact() is provided.

Link between rule.name and knowledge base.

Because of the "hidden premise" nature of a rule's name, a knowledge base automatically adds a rule's name as a fact/belief when you add a rule to the knowledge base. This automatically generated fact/belief is known as the rule hook. If the rule is proper and unnamed then the knowledge base automatically assigns the rule a name and adds that name to the knowledgebase. Care is taken that automatically assigned names do not conflict with user assigned names. To help with this process, isAutoNamed and isAutoGenerated properties are provided.

Caption and Description

Caption and Description fields allow human users to mark-up a rule with a human-readable identifier (caption) and description.

Author:

mjs (matthew.south @ cancer.org.uk)

See Also:

Serialized Form

Constructor Summary

Rule()
Default constructor.

Rule(Constant fact)
Constructor for a fact

Rule(Constant belief, java.lang.Double dob)
Constructor for a belief (a defeasible assertion, with belief less than 1.0)

Rule(Constant consequent, ElementList antecedent)
Constructor for a strict rule

Rule(Constant consequent, ElementList antecedent, java.lang.Double dob)
Constructor for a defeasible rule

Rule(Constant consequent, ElementList antecedent, java.lang.Double dob, Constant name)
General purpose constructor

Method Summary

Rule	apply(Substitution subs) Return copy of this Element with the substitution applied.
java.lang.Object	clone() An element is incompletely cloned.
boolean	equals(java.lang.Object obj)
ElementList	getAntecedent() Getter for Rule's antecendent.
java.lang.String	getCaption() Getter for caption.
java.lang.String	getClaimCaption()
java.lang.String	getClaimDescription()
Constant	getConsequent() Getter for Rule consequent.
java.lang.String	getDescription() Getter for description.
java.lang.Double	getDob() Getter for Rule's Degree of Belief.
Constant	getName() Getter for Rule name.
int	hashCode()
java.lang.String	inspect() (idea from the Ruby prototype) inspect allows us to see a representation of the text expression that the object is based on.
java.lang.String	inspect(boolean showAutoGeneratedRuleNames, boolean showRuleHooks) A version of inspect that allows you to optionally hide all of the auto generated artifacts.
boolean	isFact() Interrogation method to see if this rule actually is a rule, or a rule without a body, which is a fact.
boolean	isStrict() Check whether Rule is defeasible or strict.
void	setAntecedent(ElementList antecedent) Setter for Rule's antecedent.
void	setCaption(java.lang.String caption) Setter for caption.
void	setClaimCaption(java.lang.String claimCaption)
void	setClaimDescription(java.lang.String claimDescription)
void	setConsequent(Constant consequent) Setter for the Rule's consequent.
void	setDescription(java.lang.String description) Setter for description.
void	setDob(java.lang.Double dob) Setter for Rule's Degree of Belief.
void	setName(Constant name) Setter for Rule name.
void	write(KnowledgeWriter writer) Using the Visitor pattern, this method allows the details of an Element to be written in different ways.

Methods inherited from class org.aspic.inference.Term

addArg, getArg, isEqualModuloVariables, isGrounded, isUnifiable, negation, numberOfArgs, ruleTag, setArg, setArgList, setKnowledgeBase, unify

Methods inherited from class org.aspic.inference.Constant

getFunctor, setFunctor

Methods inherited from class org.aspic.inference.Element

getId, getKnowledgeBase, setId, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

Rule

public Rule()

Default constructor.

Rule

public Rule(Constant fact)

Constructor for a fact

Parameters:

fact - strict constant/term

Rule

public Rule(Constant belief,
            java.lang.Double dob)

Constructor for a belief (a defeasible assertion, with belief less than 1.0)

Parameters:

belief - defeasible constant/term

dob - degree of belief (0, 1.0]

Rule

public Rule(Constant consequent,
            ElementList antecedent)

Constructor for a strict rule

Parameters:

consequent - claim

antecedent - premises

Rule

public Rule(Constant consequent,
            ElementList antecedent,
            java.lang.Double dob)

Constructor for a defeasible rule

Parameters:

consequent - claim

antecedent - premises

dob - degree of belief (0, 1.0]

Rule

public Rule(Constant consequent,
            ElementList antecedent,
            java.lang.Double dob,
            Constant name)

General purpose constructor

Parameters:

consequent - claim

antecedent - premises

dob - degree of belief (0, 1.0]

name - consumer supplied rule name

Method Detail

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class Term

hashCode

public int hashCode()

Overrides:

hashCode in class Term

getConsequent

public Constant getConsequent()

Getter for Rule consequent.

Returns:

The Rule's consequent (or head).

setConsequent

public void setConsequent(Constant consequent)

Setter for the Rule's consequent.

Parameters:

consequent - A Constants or Terms.

getAntecedent

public ElementList getAntecedent()

Getter for Rule's antecendent.

Returns:

The Rule's antecedent (or tail).

setAntecedent

public void setAntecedent(ElementList antecedent)

Setter for Rule's antecedent.

Parameters:

antecedent - An ElementList of Constants or Terms.

getDob

public java.lang.Double getDob()

Getter for Rule's Degree of Belief.

Returns:

degree of belief for Rule (0, 1.0]

setDob

public void setDob(java.lang.Double dob)

Setter for Rule's Degree of Belief.

Parameters:

dob - Degree of Belief (0, 1.0]

getName

public Constant getName()

Getter for Rule name.

Returns:

the Rule's name, or null if it's not yet been set.

setName

public void setName(Constant name)

Setter for Rule name.

Parameters:

name - the rule's name to set.

inspect

public java.lang.String inspect()

Description copied from class: Element

(idea from the Ruby prototype) inspect allows us to see a representation of the text expression that the object is based on. Not implemented by overriding toString() because it's still useful to be able to inspect the objectID which toString returns.

Overrides:

inspect in class Term

Returns:

String representation of this knowledge atom

inspect

public java.lang.String inspect(boolean showAutoGeneratedRuleNames,
                                boolean showRuleHooks)

A version of inspect that allows you to optionally hide all of the auto generated artifacts.

Parameters:

showAutoGeneratedRuleNames - Allows you to hide automatically generated rule names

showRuleHooks - Allows you to hide the automatically generated "rule hook" rules

Returns:

String representing a Prolog representation of the rule.

apply

public Rule apply(Substitution subs)

Description copied from class: Element

Return copy of this Element with the substitution applied.

Overrides:

apply in class Term

Parameters:

subs - Substitution to apply

Returns:

Copy of this Element with substitution applied to it.

isFact

public boolean isFact()

Interrogation method to see if this rule actually is a rule, or a rule without a body, which is a fact.

Returns:

true if this rule is actually a fact

isStrict

public boolean isStrict()

Check whether Rule is defeasible or strict.

Returns:

true if this object is a rule and it's dob is 1.0

write

public void write(KnowledgeWriter writer)

Description copied from class: Element

Using the Visitor pattern, this method allows the details of an Element to be written in different ways.

Overrides:

write in class Term

Parameters:

writer - the object that does the writing.

clone

public java.lang.Object clone()

Description copied from class: Element

An element is incompletely cloned. Everything except it's knowledgeBase reference is cloned.

Overrides:

clone in class Term

getCaption

public java.lang.String getCaption()

Getter for caption.

Returns:

human readable identifier for rule.

setCaption

public void setCaption(java.lang.String caption)

Setter for caption.

Parameters:

caption - human readable identifier for rule.

getDescription

public java.lang.String getDescription()

Getter for description.

Returns:

Human readable description of rule.

setDescription

public void setDescription(java.lang.String description)

Setter for description.

Parameters:

description - Human readable description of rule.

getClaimCaption

public java.lang.String getClaimCaption()

setClaimCaption

public void setClaimCaption(java.lang.String claimCaption)

getClaimDescription

public java.lang.String getClaimDescription()

setClaimDescription

public void setClaimDescription(java.lang.String claimDescription)