;;; -*- Mode:Lisp; Syntax: Common-lisp; Package:ONTOLINGUA-USER; Syntax:COMMON-LISP; Base:10 -*-

;;; Standard Units and Dimensions
;;; (c) 1993 Greg Olsen and Thomas Gruber


(in-package "ONTOLINGUA-USER")

(define-theory standard-dimensions (physical-quantities)
  "This theory defines a set of physical dimensions for quantities.
It is independent of any choice of units of measure.  This set is based
on physics and economics."
  :issues ("(c) 1993, 1994 Greg R. Olsen, Thomas R. Gruber, and Yves Peligry"
	   "This theory used to be combined with standard-dimensions in a
theory called standard-units-and-dimensions.  We divided them because commitments
to one are often independent of commitments to the other."
	   (:see-also "The EngMath paper on line")))

(in-theory 'standard-dimensions)

;; The IDENTITY-DIMENSION is defined in the base theory, PHYSICAL-QUANTITIES.

(define-instance LENGTH-DIMENSION (physical-dimension) 
  "The fundamental dimension of length, as defined by the SI
standard.")

(define-instance MASS-DIMENSION (physical-dimension)
  "The fundamental dimension of mass, as defined by the SI standard.")

(define-instance TIME-DIMENSION (physical-dimension)
  "The fundamental dimension of physical, continuous time, 
as defined by the SI standard.")

(define-instance ELECTRICAL-CURRENT-DIMENSION (physical-dimension)
  "The fundamental dimension of electrical current, as defined by the
SI standard.")

(define-instance THERMODYNAMIC-TEMPERATURE-DIMENSION (physical-dimension)
  "The fundamental dimension of temperature, as defined by the SI standard.")

(define-instance AMOUNT-OF-SUBSTANCE-DIMENSION (physical-dimension)
  "The fundamental dimension of amount of substance, as defined by the
SI standard.")

(define-instance LUMINOUS-INTENSITY-DIMENSION (physical-dimension)
  "The fundamental dimension of luminous-intensity, as defined by the
SI standard.")

(define-instance FORCE-DIMENSION (physical-dimension) 

  "The physical dimension of force is defined as mass times length
over time squared.  In some systems FORCE-DIMENSION is fundamental and
MASS-DIMENSION is a derived dimension.  This theory goes with the SI
standard, but we include the definition of force as a non-fundamental
built-in dimension."

  :axiom-def (= FORCE-DIMENSION
		(* MASS-DIMENSION 
		      (* LENGTH-DIMENSION (expt TIME-DIMENSION -2)))))

(define-instance ENERGY-DIMENSION (physical-dimension) 

  "The physical dimension of energy is defined as mass times length squared
over time squared."

  :axiom-def (= ENERGY-DIMENSION 
		(* MASS-DIMENSION 
		      (* (expt LENGTH-DIMENSION 2) (expt TIME-DIMENSION -2)))))

(define-instance CURRENCY-DIMENSION (physical-dimension)
  "The fundamental dimension of currency or money.
CURRENCY-DIMENSION is to currencies as US-dollar's and ECU's as the
LENGTH-DIMENSION is to units of length such as meters.")

(define-instance area-dimension (physical-dimension)
  "The physical dimension of an area is defined as
length dimension squared."
  
  :axiom-def (= area-dimension
		(expt length-dimension 2))
  :issues ("Provided by Bernd Bachmann, DFKI"))

(define-instance pressure-dimension (physical-dimension)
  "the physical dimension of pressure is defined as 
force over area"
  
  :axiom-def (= pressure-dimension
		(* force-dimension
		   (expt area-dimension -1)))
  :issues ("Provided by Bernd Bachmann, DFKI"))

(define-instance therm^-1-dimension (physical-dimension)
  :axiom-def (= therm^-1-dimension
		(expt thermodynamic-temperature-dimension -1))

  :issues ("Provided by Bernd Bachmann, DFKI"))

(define-instance work-dimension (physical-dimension)
  :axiom-def (= work-dimension
		(* force-dimension
		   length-dimension))
  :issues ("Provided by Bernd Bachmann, DFKI"))