Annex E

(Normative)

Ring Option

E.1 Introduction

This annex contains an option which allows GT-ring objects and GT-polygon objects which are composed of GT-rings. Unless stated otherwise in this annex, all requirements of the body of this part also apply when using this option.

E.2 Spatial Objects

The following table indicates spatial object requirements which differ from that of section 2.1 of this profile.

Object Representation Code	Required	Optional	Not Permitted
RU - Ring composed of chains1	x
PC - GT-polygon			x
PR - GT-polygon12	x
PU - Universe polygon12	x
PW - Universe polygon			x
PV - Void polygon12		x
PX - Void polygon			x

1 Each of these objects must participate as a component of a 2-D manifold.

E.3 Relationship Between Modules and 2-D Manifolds

In addition to the requirements of section 4.7 (a), for objects particular to one 2-D manifold there shall be:

• one Ring module for optional simple object type RU.

The Polygon module, required by section 4.7 (a) for objects particular to one 2-D manifold, shall contain "PR", "PU", and "PV" objects when using this annex.

E.4 Transfer Module Specification

The following table contains inclusion/exclusion, and cardinality rules for additional modules permitted by this annex. The standardized modules names are included, along with the minimum number and the maximum number of occurrences of the module type. A lowercase "n" indicates that the upper limit is user defined. Any lowercase letters or dots in the module name has the meaning explained in Section 4, Standard Module Names.

Module Type	Name	Min. No.	Max. No.
Ring	RU..	1	n
Polygon1	PR..	1	n

1 This Polygon module requirement is in place of the Polygon module required by Section 5 of this profile.

A single module shall contain only records of a single object type (indicated by appropriate object representation code), with the technical exception that modules carrying "PR" (GT-polygon) records may also contain a "PU" (universe polygon) and "PV" (void polygon) records.

E.5 Module Restrictions/Requirements: Identification Module

To indicate that this annex is being used, the Profile Identification subfield shall include "/E" in the manner described in section 5.8.2 of Part 4.

E.6 Topological Pointers

When using this annex, GT-polygons, universe polygons, and void polygons shall contain pointers to ring objects which are part of the polygon; order is significant, the outer ring shall be referenced first, followed by any inner rings.

When using this annex, GT-polygons shall not have pointers to their chains.