User's Guide for the NARS Applet

Input/Output Language

The input and output of the applet are sequences of Narsese sentences, plus number of inference steps to be carried out. The following is roughly the Narsese grammar rules in BNF notation.

                        GRAMMAR RULE                         BRIEF EXPLANATION
           <sentence> ::= <statement>"." [<truth-value>]     // judgment to be remembered
                        | <statement>"?"                     // question to be answered
                        | <statement>"!" [<truth-value>]     // goal to be realized
           <statement> ::= "<"<term> <relation> <term>">"    // two terms related to each other
                        | <term>                             // a term can name a statement
           <relation> ::= "-->"                              // inheritance
                        | "<->"                              // similarity
                        | "{--"                              // instance
                        | "--]"                              // property
                        | "{-]"                              // instance-property
                        | "==>"                              // implication
                        | "<=>"                              // equivalence
                        | "=/>"                              // predictive implication
                        | "=|>"                              // concurrent implication
                        | "=\>"                              // retrospective implication
                        | "</>"                              // predictive equivalence
                        | "<|>"                              // concurrent equivalence
               <term> ::= <word>                             // an atomic constant term
                        | <variable>                         // an atomic variable term
                        | <compound-term>                    // a term with internal structure
                        | <statement>                        // a statement can serve as a term
      <compound-term> ::= "{" <term> {","<term>} "}"         // extensional set
                        | "[" <term> {","<term>} "]"         // intensional set
                        | "(&," <term> {","<term>} ")"       // extensional intersection
                        | "(|," <term> {","<term>} ")"       // intensional intersection
                        | "(-," <term> "," <term> ")"        // extensional difference
                        | "(~," <term> "," <term> ")"        // intensional difference
                        | "(*," <term> {","<term>} ")"       // product
                        | "(/," <term> {","<term>} ")"       // extensional image
                        | "(\," <term> {","<term>} ")"       // intensional image
                        | "(--," <term> ")"                  // negation
                        | "(||," <term> {","<term>} ")"      // disjunction
                        | "(&&," <term> {","<term>} ")"      // conjunction
                        | "(&/," <term> {","<term>} ")"      // sequential events
                        | "(&|," <term> {","<term>} ")"      // parallel events
                        | "(/>," <term> ")"                  // future event
                        | "(|>," <term> ")"                  // present event
                        | "(\>," <term> ")"                  // past event
           <variable> ::= "#"<word>                          // independent variable
                        | "#"<word> "(" {"#"<word>} ")"      // dependent variable
                        | "#"                                // anonymous term as place holder
                        | "?"<word>                          // query variable for term to be find
        <truth-value> ::= "%"<frequency>";"<confidence>"%"   // two real numbers in [0,1]
               <word> : string in an alphabet

Graphical User Interface

Main Window

This window contains a menu bar, a text area, a clock field, and four command buttons.

• The following menu items are available in the applet version of NARS:
• Memory/[Initialize]: vacate the memory.
• View/[Concepts]: open a Bag Window to display all concepts.
• View/[Task Buffer]: open a Bag Window to display the new tasks to be processed.
• View/[Inference Log]: show the Inference Log Window.
• View/[Input Window]: show the Input Window.
• Parameter/[Task Forgetting Rate]: control how fast the priority values of tasks decay, in a Parameter Window.
• Parameter/[Belief Forgetting Rate]: control how fast the priority values of beliefs decay, in a Parameter Window.
• Parameter/[Concept Forgetting Rate]: control how fast the priority values of concepts decay, in a Parameter Window.
• Parameter/[Report Silence Level]: indicate the resource-budget threshold for derived tasks to be reported to the user, in a Parameter Window.
• Help/[Related Information]: display pointers to NARS related information in a Message Window.
• Help/[About NARS]: display version and copyright information of NARS in a Message Window.
• The text area displays the conversation between the user and the system.
• Lines preceded by "IN:" are input provided by the user.
• Lines preceded by "OUT:" are output provided by the system.
• Lines consist of single integers record the number of inference steps between input/output events.
• The Clock field is a counter of inference steps after the last input/output event.
• The command buttons correspond to basic operations:
  • "Run": start the inference engine.
  • "Walk": let the inference engine work for one cycle.
  • "Stop": stop the inference engine.
  • "Exit": exit NARS.

Input Window

This window contains a text area and four command buttons.

• The text area allows the user to type or paste input lines, each of which may be
• a judgment, which is a statement with a (optional) truth value (a frequency-confidence pair).
• a question, which is a statement without truth value, and may contain query variable to be instantiated.
• a goal, which is a statement to be realized, with a (optional) truth value indicating how much it is desired.
• a number, indicating the inference steps between input events.
• a blank line, indicating a pause in the input.
• The command buttons correspond to basic operations:
• "OK": feed the current lines into the system.
• "Hold": stop feeding the lines.
• "Clear": clear the text field.
• "Hide": hide the window.

Inference Log Window

This window contains a text area and three command buttons.

• The text area displays information in each inference step, including
• a step serial number.
• the concept selected in the step.
• the task selected in the step, if any.
• the belief selected in the step, if any.
• the new task(s) derived in the step, if any.
• The command buttons correspond to basic operations:
• "Play": display the information..
• "Stop": stop displaying.
• "Hide": hide the window.

Bag Window

This window contains a text area, a slider, and three command buttons.

• The text area displays the items in the bag, according to their priority levels.
• The slider indicates and adjusts the priority threshold for items to be displayed.
• The command buttons carry out the following operations:
• "Play": display the information.
• "Stop": stop displaying.
• "Close": close the window.

Parameter Window

This window contains a slider and three command buttons.

• The slider indicates and adjusts the current parameter value.
• The command buttons carry out the following operations:
• "Undo": reset the parameter to its previously saved value.
• "Default": reset the parameter to its default value.
• "Hide": save the current value and hide the window.

Message Window

This window contains a text area and a bottom.

• The text area displays a message to the user.
• The "OK" button closes the window.

Color Usage

• Window color:
  • blue for the main window.
  • purple for a window that has only one instance in the system.
  • green for a window that may have more than one instance in the system.
• Text background color:
  • white means can be edited.
  • light-cyan means display only.