BOOL OPERAND

A CONSTRUCT is an entity that has a scope. The data structure of a construct represents a three-dimensional geometrical shape. Certain domains of this shape may have material properties associated with them. A construct is not an elementary solid model but defines a function which -when evaluated- will produce a solid. The function operators are BOOLEAN, the operands are of type BOOL OPERAND. The elementary operands which are called PRIMITIVE entities exist in the scope of the CONSTRUCT only. However, POLYHEDRON models and B REP entities may exist in the construct scope and may be used as operands to boolean operations (if the CAD system provides this capability). The attribute result is an instance of the BOOLEAN which represents the root of the boolean tree or simply of a PRIMITIVE, B REP, POLYHEDRON, or another CONSTRUCT. 

REFERENCE(BOOL OPERAND) REFERENCE(BOOL OPERAND) ... 

BOOL OPERAND is a class of entities which can occur as an operand to a BOOLEAN operation using regularized boolean operators (see e.g. A.A.G.Requicha and H.B.Voelcker, Solid Modeling, in IEEE Computer Graphics and Applications, Vol.2, No.2, Mar. 1982, pp.9-24)... 

BOOL OPERATOR is an attribute that defines whether the two operands of a boolean expression are to be combined as a difference (first operand minus second operand), union, or intersection. 

---