###

    # KEHOME/knowledge/theory/KRdesign/variable.html
    # 1999/1/20
    # new syntax Sep/29/2002

    #===========#
    # variables #
    #===========#

    variables are used in

        every variable is   clist    { ... $variable ... }
        every variable isa  cname    { ... $variable ... }
        every variable isin relation { ... $variable ... }
        every variable isin method   { ... $variable ... }

        m is method with
    	format=[class:1,...],
    	meaning={... $1 ...}

        r is relation with
    	format=[class:1,...],
    	meaning={... $1 ...}

        set . = concept  # current concept

    To facilitate accessing the attributes and actions of the
    current concept, set records the following $ variables:

        $class	# list of all class (concept isa* class)
        $genus	# list of all genus (more than one for a lattice)
        $unit	# list of all units
        $alias	# list of all aliases
        $attribute	# list of all attributes
        $attr	# value of an individual attr
        $action	# list of all actions
        $act	# event of an individual act
        $1,$2,...	# role values of a relation unit
        $fact	# input text (if applicable)

General References