Definition

1. For any spatial-index-related organization SIRO,

   1.1	The column_width of SIRO shall be a positive number.
   1.2	The row_width of SIRO shall be a positive number.
   1.3	For each branch of the organization, the corresponding <Spatial Index Data> shall define a region in the spatial index, such that
   	1.3.1 The column_index of the <Spatial Index Data> instance shall be between 1 and the column_count defined by SIRO. 1.3.2 The row_index of the <Spatial Index Data> instance shall be between 1 and the row_count defined by SIRO. 1.3.3 Each primitive within the branch shall have a spatial extent overlapping that defined by the <Spatial Index Data> of the branch.

2. Consider an instance SRA, which is either a <Spatial Index Related Features> or a <Spatial Index Related Geometry>.

   2.1	If SRA's strict_organizing_principle = SE_TRUE, then for each branch of SRA, each primitive within the branch shall have a spatial extent fully contained within that defined by the <Spatial Index Data> corresponding to the branch. (If SRA's strict_organizing_principle = SE_FALSE, then no guarantees exist as to how accurately the instances of the component tree rooted at SRA were placed into their "sorted bins" (the branches of SRA), apart from that specified by 1.)
   2.2	If SRA is a <Spatial Index Related Features>, and the same <Feature Representation> instance belongs to more than one of its branches, then the unique_descendants and strict_organizing_principle flags of SRA shall be set to SE_FALSE.
   2.3	If SRA is a <Spatial Index Related Geometry>, and the same <Geometry Representation> instance belongs to more than one of its branches, then the unique_descendants and strict_organizing_principle flags of SRA shall be set to SE_FALSE.

Rationale

1. Each branch of a spatial-index-related organization is intended to organize instances that fall within the specified spatial-index for that branch.

2. The strict_organizing_principle flag of <Spatial Index Related Features> and <Spatial Index Related Geometry> was designed to allow the use of spatial-index-related organization, even when a few primitives cross the boundaries of the organizing principle.

Example

1. Consider a <Spatial Index Related Geometry> instance with row_count = 1, column_count = 4, row_width = 1000 metres, column_width = 1000 metres. For simplicity, each of the 4 branches of the <Spatial Index Related Geometry> in this example is a <Union Of Primitive Geometry>.

   

   Since the origin of the collection (its lower-left corner, the <TM Augmented 3D Location> is (0, 0, 0), the coverages of the branches are:

   1. from (0, 0) to (1000, 1000)
   2. from (1000, 0) to (2000, 1000)
   3. from (2000, 0) to (3000, 1000)
   4. from (3000, 0) to (4000, 1000)
   (Note that a <Spatial Index Related Geometry> does not specify the range of z/height/elevation values.)

   Consider a triangular <Polygon> in branch #2 of this aggregation, with <Vertex> <Location> instances (1995, 0, 0), (2005, 0, 0) (2005, 10, 0).

   Since this <Polygon> crosses the boundary between branch #2 and branch #3, this <Spatial Index Related Geometry>'s strict_organizing_principle shall be set to SE_FALSE.

2. Consider a <Spatial Index Related Features> with row_count = 1, column_count = 4, row_width = 1000 metres, column_width = 500 metres. For simplicity, each of the 4 branches of the <Spatial Index Related Features> instance in this example is a <Union Of Features> instance.

   

   Since the origin of the collection (its lower-left corner, the <TM Augmented 3D Location> is (0, 0, 0), the coverages of the branches are:

   1. from (0, 0) to (500, 1000)
   2. from (500, 0) to (1000, 1000)
   3. from (1000, 0) to (1500, 1000)
   4. from (1500, 0) to (2000, 1000)

   (Note that a <Spatial Index Related Features> does not specify the range of z/height/elevation values.)

   Consider a triangular <Areal Feature> in branch #2 of this aggregation, consisting of one regular <Feature Face>, which in turn has an external Feature Face Ring containing 3 <Feature Edge> instances as follows:

   

   Since the <Areal Feature> thus crosses the boundary between branch #2 and branch #3, the <Spatial Index Related Features>' strict_organizing_principle shall be set to SE_FALSE.

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