Class Name: Spatial Index Related Feature Topology

Superclass - Topology Hierarchy

Definition

Encodes a spatially indexed (tiled) organization of the primitive Feature Topology objects (Feature Nodes, Feature Edges, and Feature Faces within a SEDRIS transmittal.

Primary Page in DRM Diagram:

• 11

Example

An Aggregate Feature can have more than one spatial organization for its topology. This allows various 'levels' or organizations. Perhaps at the 'top' Aggregate Feature under the Environment_Root, you might find one 10km by 10km spatial organization of topology spanning the entire transmittal, as well as one 500m by 500m spatial organization of topology also spanning the entire transmittal. That 'top' Aggregate Feature would have two Spatial Index Related Feature Topology components, one for the 10km squares and one for the 500m squares.

FAQs

Why not restrict Spatial Index Related Feature Topology to be a component of just Environment_Root and Model - placing Topology as an organizing principle on par with Geometry organizations and Feature organizations?

We must be able to spatially organize the topology of every 'topological surface'. A 'topological surface' is not necessarily 'rooted at' a Environment_Root or a Model object. In general, we allow for many different 'topological surfaces' to exist within a Environment_Root or a Model.

Why an aggregate object instead of a hierarchy or some other type of SEDRIS object?

We need a 'branch', and each branch from an Aggregation is a Hierarchy object, because Aggregate Feature objects objects contain objects. When you cross through an Aggregate Feature object where the independent_topologies field is set to true, then each 'branch' from such an object represents a distinct topological surface. We must organize a topological surface, a.k.a. an "independent topology", which eventually, in SEDRIS, is 'rooted at' a single Aggregate Feature object. The Feature Hierarchy objects are either Aggregate Features or Feature Model Instances. The topological organization of the Model, if any, is contained within the Model, so we're left with a need to specify the topological organization of an Aggregate Feature object. The organizing principle must be applied at the Aggregate Feature level - no lower, no higher.

The same spatial indexing structure can be shared by multiple Aggregate Features because there could exist multiple classification organizations of the same set of Features. When a single set of Features is organized by multiple classification approaches, it's still the same set of Features being dealt with, and still the same set of Feature Nodes, Edges, and Faces. Changing the logical organization of the Features has no effect on the spatial organization of the underlying topological primitives. Thus, one spatial organization for a set of topological primitives may be shared by many different organizations (aggregations) of Features where the Features are composed of the same spatially organized topological primitives, regardless of which organization the Features are viewed from.

Does Spatial Index Related Organizing Principle cover Spatial Index Related Feature Topology?

No. Spatial Index Related Feature Topology implicitly uses a strict organizing principle, since it does not have a flag allowing the data provider to specify that such a principle is not used.

Constraints

• Distinct Link Objects

Composed of (one-way)

• one Location (notes)

Composed of (two-way)

• one or more Union of Feature Topologies through Feature Topology Spatial Index Data

Component of (two-way)(inherited)

• one or more Aggregate Features

Field Elements

Notes

Composed of Notes

Location

 The origin of the collection.  The lower-left corner.

Fields Notes

column_width

 length of a cell in the given units along the X axis

row_width

 length of a cell in the given units along the Y axis