Abstract Class Name: Feature Hierarchy

Superclass - Feature

Subclasses

• Aggregate Feature
• Feature Model Instance

Definition

A hierarchically organized collection of Features, which can be either an Aggregate Feature or a Feature Model Instance.

Primary Page in DRM Diagram:

• 8

Secondary Pages in DRM Diagram:

• 1
• 2
• 7
• 21

Example

1. A collection of Features representing an entire transportation network, including roads, railroads, and airfields.

FAQs

What distinguishes the Feature Hierarchy class from the Feature and Aggregate Feature classes?

Unlike a Feature, a Feature Hierarchy may not consist of a single Primitive Feature. Unlike an Aggregate Feature, a Feature Hierarchy may be a Feature Model Instance.

Can Level 0 feature topology be represented in SEDRIS?

Yes. Although in VPF, for example, the mere presence of Connected Nodes implies Level 1 topology, this is not the case in SEDRIS. The SDRM requires Feature Nodes to exist to contain the endpoint coordinates of Feature Edges. Consequently, the presence of Feature Nodes means nothing by itself. If, within a single topological layer, any two different Feature Nodes have the same Location coordinates, the topology level is Level 0. If no two Feature Nodes have identical Location coordinates, the topology level is (at least) Level 1.

Which objects (and relationships) are required to exist at each feature topology level?

At Level 0, unless the data consists solely of isolated (i.e., entity) Feature Nodes, the following objects (and the relationships among them) are all required to exist:

• Feature Edge
• Feature Edge Starting Node
• Feature Edge Ending Node
• Feature Node
• Connected Feature Edge

All other types of feature topology objects and relationships MAY also exist at Level 0, but the requirements of Level 1 are NOT met.

At Level 1, no additional objects or relationships are required. However, each Feature Node must have a unique Location (i.e., two or more Feature Nodes cannot be colocated).

At Level 2, no additional objects or relationships are required. However, Feature Edges may not intersect or overlap one another, except where they meet at a common Feature Node.

At Level 3, the remaining objects and relationships are required to exist:

• Feature Face (Regular and Universal)
• Feature Face Ring (External and Internal)
• Bordered Feature Face
• Contained Feature Node
• Contained Within Feature Face

The set of Feature Faces must be exclusive and exhaustive, forming a complete surface (i.e., Feature Faces may not intersect or overlap one another, except where they meet at a common Feature Edge). Exactly two Feature Faces border each Feature Edge.

At Level 4, Location 3Ds are required, and there must be at least one case where more than two Feature Faces meet at a single Feature Edge.

Why can't a Reference Surface be associated to a Feature Hierarchy, as with Geometry Hierarchy?

A Reference Surface is associated to a Geometry Hierarchy to indicate that the Geometry Hierarchy contains a resolution surface. Feature Hierarchies are not used to represent Reference Surfaces.

Constraints

• Image Mapping Functions and Texture Coordinates
• No Attribute Conflicts
• Non Crossing Aggregations
• Non Crossing Associations
• Precedence of Attribute Set Index
• Non Cyclic Aggregations

Associated by (one-way)

• optionally, a Hierarchy Summary Item

Associated with (two-way)(inherited)

• optionally, some Features
• optionally, some Geometry Hierarchies
• optionally, some Property Grids

Composed of (one-way)(inherited)

• optionally, some {ordered} Attribute Set Indices
• optionally, a Classification Data
• optionally, some Colors
• optionally, some {ordered} Image Mapping Functions (notes)
• optionally, some Labels
• optionally, some Property Tables
• optionally, some Property Table References
• optionally, some Property Values
• optionally, a Rendering Priority Level
• optionally, a Spatial Domain

Composed of (one-way)

• optionally, a Reference Surface
• optionally, some Sound Instances

Composed of (one-way metadata)(inherited)

• optionally, an Access
• optionally, some Browse Graphics
• optionally, some Cross References
• optionally, a Data Quality
• optionally, a Keywords
• optionally, a Point of Contact
• optionally, a Time Constraints Data

Component of (two-way)(inherited)

• optionally, some Union of Features

Component of (two-way)

• optionally, some Alternate Hierarchy Related Features through Feature Hierarchy Data
• optionally, some Classification Related Features through Feature Classification Data
• optionally, an Environment Root
• optionally, a Feature Model
• optionally, some Time Related Features through Feature Time Constraints Data
• optionally, some Level of Detail Related Features through Feature Level of Detail Data
• optionally, some Oct Tree Related Features through Feature Oct Tree Data
• optionally, some Perimeter Related Features through Feature Perimeter Data
• optionally, some Quad Tree Related Features through Feature Quad Tree Data
• optionally, some Spatial Index Related Features through Feature Spatial Index Data
• optionally, some State Related Features through Feature State Data

Field Elements

Notes

Composed of Notes

Image_Mapping_Function

 Added to support "attributes for derived objects."
 That is, these components are used only to specify
 texture mapping information for geometry that
 is derived from the <Feature> by the consumer.
 These <Image Mapping Functions> must use
 <Image Anchor> components to specify the mapping.