scale.annot
Class Support

java.lang.Object
  scale.annot.Support

public class Support
extends java.lang.Object

This class represents the support level for an annotation.

$Id: Support.java,v 1.24 2007-08-13 12:32:02 burrill Exp $

Copyright 2007 by the Scale Compiler Group,
Department of Computer Science
University of Massachusetts,
Amherst MA. 01003, USA
All Rights Reserved.

A particular support for annotations.

The belief values and combination rule are specified using enumerations, which are as follows:

• Belief: This value represents the strength of belief. Both user and system beliefs are specified with this enumeration.
  • false
  • improbable
  • unlikely
  • neutral
  • possible
  • probable
  • true
  The value neutral expresses no belief, positive or negative, and is therefore identical to the annotation not existing. For many annotations, the absence of an annotation implies a value; hence in these cases, neutral will be equivalent to one of false or true. To make dealing with this unfortunate situation easier, I would like the elements of the enumeration to have a method that returns an integer value (e.g., value() or order()), so that we can do something like the following:

       if (ann.belief().value() <= cNeutral)
           // annotation is false.
       else
           // annotation is true.
     

  False is less than true, and the values are ordered as shown above. Generally, neutral is used to indicate that an annotation is to be ignored.

  For some annotations, beliefs do not make sense. For example, an annotation indicating originating source position is inherently true. Nevertheless, they will be assigned beliefs.

• Combining rule: The combining rule specifies how the user and system belief values will be combined.
  • cStrongestSystem: Use whichever value represents the strongest belief. In the case of a tie, use the system's value. Strength is the distance from neutral
  • cStrongestUser: Use whichever value represents the strongest belief. In the case of a tie, use the user's value.
  • cSystem: Use the system's value.
  • cUser: Use the user's value
  • cOptismistic: Return whichever value reprsents the more optimistic belief.
  • cPessimistic: Return whichever value reprsents the more pessimistic belief.
  cStrongestSystem is the default rule, and is automatically set by the annotation constructor. The combination rule field is mutable, and may be changed to something other than the default by calling a method of the annotation class.

This table lists some sample situations and the appropriate settings for the belief and combination rule fields. The combination rule should always be the default, unless otherwise specified.

Situation	User belief	System belief	Combining rule
User creates annotation	possible	neutral	default
Annotation derived from source language construct	neutral	true	default
Annotation from an accurate analysis	neutral	true	default
Annotation from a conservative analysis	neutral	probable	default
User overrides annotation created by system	neutral	unchanged	user
System choses to drop a user annotation	unchanged	neutral	system

See Also:

Annotation

Nested Class Summary

static class	Support.Belief Annotations retain a measure of belief in the accuracy of the annotation.
static class	Support.Rule The combining rule specifies how the user and system belief values will be combined.

Field Summary

static Support

systemTrue System belief is true.

Method Summary

Support	combine(Support a) Combine two supports.
static Support	create(boolean isUser, Support.Belief belief)
static Support	create(Support.Belief user, Support.Belief system, Support.Rule rule) Re-use an existing instance of a particular support.
Support.Rule	getRule() Return the rule used in the support.
Support.Belief	getSystemBelief() Return the user system used in the support.
Support.Belief	getUserBelief() Return the user belief used in the support.
java.lang.String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

systemTrue

public static final Support systemTrue

System belief is true.

Method Detail

create

public static Support create(Support.Belief user,
                             Support.Belief system,
                             Support.Rule rule)

Re-use an existing instance of a particular support. If no equivalent support exists, create a new one.

create

public static Support create(boolean isUser,
                             Support.Belief belief)

combine

public Support combine(Support a)

Combine two supports.

Returns:

the new Support

getRule

public final Support.Rule getRule()

Return the rule used in the support.

getUserBelief

public final Support.Belief getUserBelief()

Return the user belief used in the support.

getSystemBelief

public final Support.Belief getSystemBelief()

Return the user system used in the support.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object