Shape Validation in ArcSDE 9.1

ArcSDE maintains valid shapes internally by applying a set of rules to each shape type. All ArcSDE commands that create or update shapes use these rules.

Verification rules for point shapes are:
- The area and length of points are set to 0.0.
- A single point's envelope is equal to the point's x,y values.
- The envelope of a multipart point shape is set to the minimum bounding box.

Verification rules for simple lines, or linestring shapes, are:
- Sequential duplicate points are removed.
- Each part must have at least two distinct points.
- Each part may not intersect itself. The start and endpoints may be the same, but the resulting 'ring' is not treated as an area shape.
- Parts may touch each other at the endpoints.
- The length is the sum of all the parts.

Verification rules for lines, or spaghetti shapes, are:
- Lines can intersect themselves.
- Each part must have at least two distinct points.
- Sequential duplicate points are deleted.
- The length is the length of all of its parts added together.

Verification rules and operations on area shapes are:
- Delete duplicate sequential occurrences of a coordinate point.
- Delete dangles.
- Verify that the line segments close (z coordinates at start and endpoints must also be the same) and don't cross.
- Correct rotation to counterclockwise (see the previous section for an explanation of how ArcSDE stores area shapes).
- For area shapes with holes, ensure that holes reside wholly inside the outer boundary. ArcSDE eliminates any holes that are outside the outer boundary.
- Convert a hole that touches an outer boundary at a single common point into an inversion of the area shape.
- Combine multiple holes that touch at common points into a single hole.
- Multipart area shapes may not overlap. However, two parts may touch at a point.
- Multipart area shapes may not share a common boundary. Common boundaries are dissolved.
- If two rings have a common boundary, they are merged into one ring.
- Calculate the total geometry perimeter, including the boundaries of all holes in donut polygons, and store the perimeter as the length of the geometry.
- Calculate the area.
- Calculate the envelope.