4 Information requirements

This clause specifies the information requirements for the Topologically bounded surface application module. The information requirements are specified as the Application Reference Model (ARM) of this application module.

NOTE 1  A graphical representation of the information requirements is given in Annex C.

NOTE 2  The mapping specification is specified in 5.1. It shows how the information requirements are met by using common resources and constructs defined or imported in the MIM schema of this application module.

This clause defines the information requirements to which implementations shall conform using the EXPRESS language as defined in ISO 10303-11. The following begins the Topologically_bounded_surface_arm schema and identifies the necessary external references.

4.1 Required AM ARMs

The following EXPRESS interface statements specify the elements imported from the ARMs of other application modules.

EXPRESS specification:

*)
USE FROM Basic_geometric_topology_arm;    --  ISO/TS 10303-1323



USE FROM B_spline_geometry_arm;    --  ISO/TS 10303-1801
(*



NOTE 1   The schemas referenced above are specified in the following part of ISO 10303:

Basic_geometric_topology_arm	ISO/TS 10303-1323
B_spline_geometry_arm	ISO/TS 10303-1801

NOTE 2   See Annex C, Figures C.1and C.2 for a graphical representation of this schema.

4.2 ARM entity definition

This subclause specifies the ARM entity for this module. The ARM entity is an atomic element that embodies a unique application concept and contains attributes specifying the data elements of the entity. The ARM entity and definition is specified below.

4.2.1 Advanced_face   

The following constraints apply:

• An Advanced_face is required to be fully bounded by edge loops or by vertex loops;
• At most one of the bounds of the face may define the outer bound;

  NOTE    For some types of closed or partially closed surfaces, it may not be possible to identify a unique outer bound.

  EXAMPLE 1   Any edge loop on a plane surface may be used to define a face outer bound provided it is not enclosed in any other loop in the face.

  EXAMPLE 2   A circular loop on a cylindrical surface cannot define a face outer bound since it does not enclose a closed domain in the surface.

• The geometry used in the definition of the face shall be restricted. The face geometry shall be an elementary surface, swept surface, or b-spline surface;
• The geometry of all bounding edges of the face shall be fully defined as edge curves;
• The types of curve used to define the geometry of edges shall be restricted to lines, conics, polylines, surface curves, or b spline curves;
• All vertices used in the face definition shall be of type vertex point with geometry defined by a cartesian point;
• The use of oriented paths in the definition of the edge loops of the advanced face is prohibited;
• If the face geometry is a swept surface then the swept curve used in the definition shall be a line, conic, polyline, or a b-spline curve;
• For any vertex loop used to bound the face, the loop vertex shall be a vertex whose geometry shall be defined by a cartesian point;
• The face bounds shall be defined by either edge loops or vertex loops;
• If a surface curve is used as part of a face bound then the associated geometry attribute shall reference pcurves not surfaces;
• If a polyline is used either to define a swept surface or as part of a face bound, it shall contain at least three points;
• Any instance of advanced face which has the geometry of a complete spherical surface shall be bounded by a vertex loop located at the point where the z axis of the placement coordinate system leaves the surface of the sphere, (that is, at the North Pole of the sphere).

EXPRESS specification:

*)
ENTITY Advanced_face
  SUBTYPE OF (Face_surface);
END_ENTITY;
(*

© ISO 2014 — All rights reserved