adding model type metadata

source/mmt/Quantities.mmt

@@ -4,26 +4,31 @@ import qe http://mathhub.info/MMT/physics-units
 /T   This is a theory containing the electric displacement. 
 
 theory Displacement : qe:?QEBase  =
+        meta modeltype physical_quantity 
 	displacement_dim : type  = QE (ElectricCharge /' (SIlength * SIlength)) 
 	displacement :  displacement_dim  # D 
 
 	
 theory Permittivity : qe:?QEBase  =
+        meta modeltype physical_quantity 
 	permittivity_dim : type  = QE (ElectricCharge /' (ElectricPotential * SIlength)) 
 	permittivity :  permittivity_dim  # εs 
 
 	
 theory Density : qe:?QEBase =
+        meta modeltype physical_quantity 
 	density_dim : type  = QE (DimNone /' (SIlength * SIlength * SIlength)) 
 	density : density_dim 
 
 	
 theory CurrentDensity : qe:?QEBase =
+        meta modeltype physical_quantity 
 	currentdensity_dim : type  = QE (SIcurrent /' Area) 
 	currentdensity : currentdensity_dim 
 
 	
 theory RecombinationRate : qe:?QEBase =
+        meta modeltype physical_quantity 
 	recombinationrate_dim : type  = QE (DimNone /' (Volume * SItime)) 
 	recombinationrate : recombinationrate_dim  # R 
-
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+