PlanarCurve fixes per review. Objects, forgot b4.

Author: conradbock

sysml.library/Domain Libraries/Geometry/ShapeItems.sysml

@@ -14,10 +14,10 @@ package ShapeItems {
 	private import ControlFunctions::'?';
 
 	/**
-	 * A PlanarCurve is a flat Surface with a given area.
+	 * A PlanarCurve is a Curve with a given length embeddable in a plane.
 	 */
 	item def PlanarCurve :> Curve {
-		attribute :>> area [1] ;
+		attribute :>> length [1] ;
 
 		constraint { notEmpty(outerSpaceDimension) &  outerSpaceDimension <= 2 }
 	}

sysml.library/Kernel Library/Objects.kerml

@@ -16,7 +16,8 @@ package Objects {
 	private import SequenceFunctions::notEmpty;
 	private import SequenceFunctions::union;
 	private import CollectionFunctions::contains;
-	private import ScalarValues::Integer;	     
+	private import ScalarValues::Integer;
+	private import ScalarValues::Natural;
 
 	/**
 	 * Object is the most general class of structural occurrences that may change over time.
@@ -81,9 +82,9 @@ package Objects {
 	struct all Surface specializes Object {
 		feature redefines innerSpaceDimension = 2;
 		  /* The number of  "holes" in this Surface, assuming it isClosed. */
-		feature genus : Integer[0..1] default 0;
+		feature genus : Natural[0..1] default 0;
 
-		inv { notEmpty(genus) implies (isClosed & genus >= 0) }
+		inv { notEmpty(genus) implies isClosed }
 	}
 
 	/*