For a general introduction to inexact rules see What are inexact rules? Rule-type specific windows and issues are explained in Inexact Rules Types. See also inexact rule related input facilities for a description "question series" and "question clusters".

Certainty rules and fuzzy sets (fuzzy set rules) are "subordinated" to sentence rules in the way that their ultimate purpose is to return a certainty factor probability or a membership grade to a data element type in the conclusion of a sentence rule. Certainty rules and fuzzy sets are used by (called by) the sentence rule in the same way as functions. The inference engine however deals with functions and certainty rules/fuzzy sets differently. While functions are handled by the core PROLOG-type inference engine, certainty rules and fuzzy sets are handled by special engine used for certainty rules only.  

INEXACT RULE COMPONENTS

An inexact rule consists of three parts:

• terminology
• sentence model declaration
• inexact rule definition

Normally, you have to insert these three elements in the KB in the sequence over, and remove (delete) from the KB in the reversed over. 

The terminology defines the rule's KB name and NL name. The sentence model declaration defines the rule's parameters as an ordered list of data element types, and the domain of the rule's return value. The inexact rule definition defines the mapping from parameters to return value (the "program code").

Example

TERMINOLOGY

the syntagm with language English, KB-name "cPowerfulBike", syntax class INEXACT_RULE, syntax form SINGULAR_UNDETERMINED and token list "powerful" and "bikes" is in the terminology with segment name "MC"!

SENTENCE MODEL

the inexact rule with NL-name powerful bikes, domain name MEMBERSHIP_GRADE and data element list model name is in the sentence model with segment name "MC"!

DEFINITION

There is no representation of an inexact rule definition on NL-format. However, inexact rules have an XML-format representation which incorporates the definition as well as the sentence model declaration:

<inexactRule format="NL" realm="INEXACT_RULES">
<queryRule>
<heading>
<rule>powerful bikes</rule>
<returnDomain>MEMBERSHIP_GRADE</returnDomain>
<parameter>model name</parameter>
<prior>0</prior>
</heading>
<default>
<intVal>50</intVal>
</default>
<query>first value of bhp where bike with model=this model name has metric specifications</query>
<map>
<mapClass>NUMERIC</mapClass>
<intVal>100</intVal>
<intVal>1</intVal>
<intVal>50</intVal>
<fixVal>0.5</fixVal>
<intVal>20</intVal>
<intVal>0</intVal>
</map>
</queryRule>
</inexactRule>
 

Inexact Rules Main Window

Creating a New Rule

You can change the rule type by deleting and then re-creating the rule with the new type. However, this has the disadvantage that knowledge nodes with references to the rule must be deleted or suspended. To avoid this you can instead use the following procedure:

1. Delete the rule's definition in the Inexact Rules-window (i.e. retain the declaration to avoid creating referential problems).
2. In the same window, select the new rule type and press New Rule-button.
3. Enter the rule's NL- and KB-names (the spelling must be identical to existing rue declaration).
4. Re-enter the appropriate rule definition.

INPUT PARAMETERS

Input parameters (which are data element types) are selected from the list button on the right side (you can also type in the data element name rather than selecting it). Use the Look up data element to open the data element window i.e. to see the definition of a selected data element type, or to define a new. The Refresh-button is used to refresh the list (e.g. if you have defined a new data element type).

Use the <---Add-button to add the selected data element as a new input parameter (i.e. include in the left-side listbox). The Remove--->-button removes an existing parameter. The Move Up and Move Down-buttons are used to change the sequence of the selected input parameters. Note that the sequence is significant such that existing calls to the rule (if any) must be modified if the sequence is changed.

Calling Rules - Rule Call Dialog

If an input parameter in the selected rule has the same name as one of the calling rule's parameters, then this parameter is assigned to it by default (to save data entry effort - you can of course change the value assigned to the parameter as something else).

Setting/re-setting actual parameter values:

Select the parameter in the list-box. Then type the actual parameter value in the edit-control on the right side of the (Re-)set parameter value-button and press the button. The typed value must be of the same domain as the parameter.

All parameters must have a value assigned to it before the OK-button is pressed.

CALL-TYPE SPECIFIC CONTROLS

Some call-types need additional details related to or qualifying the call.

CALL SYNTAX-FORMATS (AS DISPLAYED)

The syntax conventions used for displaying calls in the various inexact rule windows are mostly self-explanatory. The call proper is shown as follows:

• <Call> ::= called_rule [ <Parameter> [{, <Parameter>}* and <Parameter>] ]
• <Parameter> ::= parameter_name = <Value>
• <Value> ::= this parameter_name | calling_rule's parameter_name | literal_value

A context call is associated with a value or a range of values for which the calling rule is deemed to be in context:

• <ContextCall> ::= <Range> :: <Call>
• <Range> ::= {=|<>|<|<=|>|>=} literal_value [& {=|<>|<|<=|>|>=} literal_value ]

A switch call additionally has a default-option:

<SwitchCall> ::= ::= <Range> :: <Call> | default :: <Call>

A call in a bayesian combination has increment and decrement values, which either are literal values or another call:

<BayesianCall> ::= ::= <Call> :: INC: {<Call> | literal_value>} DEC: {<Call> | literal_value>}

A reference (call) in an ordered weighted average (OWA) fuzzy set combination has a weight value, which either is literal values or another call:

<OWA_Call> ::= ::= <Call> :: WEIGHT: {<Call> | literal_value>}

A call to a parameter-returning rule in a parameter rule is shown as:

<ParamaterCall> ::= ::= variable :: <Call>

Rule Networks - Rule Trees

Pro/3 can draw rule networks as trees. Rule trees are drawn with the calling rule to the left of the rules called. The example under shows a portion of rule network from the MC-model: